WBBSE Class 9 Life Science Solutions Chapter 4.1 Immunity and Human Diseases

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 4.1 Immunity and Human Diseases offer valuable context and analysis.

WBBSE Class 9 Science Chapter 4.1 Question Answer – Immunity and Human Diseases

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Which type of immunity develops by birth?
Answer:
Innate immunity develops by birth.

Question 2.
Which characteristic ability of antigen activates the immune system of the body?
Answer:
Immunogenicity of antigen activates the immune system of the body.

Question 3.
Which characteristic ability of antigen makes it compatible to the antibody?
Answer:
Antigenicity of an antigen makes it compatible to the antibody.

Question 4.
What is the name of the reaction shown by the body against any pathogen?
Answer:
The reaction shown by the body against any pathogen is commonly called immuneresponse.

Question 5.
What are allergens?
Answer:
The substances which trigger allergies are called allergens.

Question 6.
What is the name of the chemical, which is produced inside the body to resist a toxin?
Answer:
Antitoxin is produced inside the body to resist a toxin.

Question 7.
Which is the most abundant antibody present in human blood?
Answer:
Immunoglobulin G is the most abundant antibody present in human blood.

Question 8.
Which type of antiborly is present in ditierent body fluids and secretory materials in human body?
Answer:
Immunoglobulin A is present in different body fluids and secretory materials in the human body.

Question 9.
Which is the largest antibody present in our body?
Answer:
Immunoglobulin M is the largest antibody present in our body.

Question 10.
In which antibody five molecules stay as a ciuster?
Answer:
In Immunoglobulin M, five molecules stay as a cluster.

Question 11.
Where do B-lymphocytes mature?
Answer:
B-lymphocyte or B-cells mature in red bone marrow.

Question 12.
Which type of immunity is provided by neutrophils?
Answer:
Neutrophils provide innate immunity to the body.

Question 13.
How does an immunoglobulin G molecule appear?
Answer:
Immunoglobulin G molecules appear like English letter ‘Y’.

Question 14.
How many globulin chains combine to prepare an immunoglobulin G molecule?
Answer:
Two heavy and two light globulin chains combine to prepare an immunoglobulin G molecule.

Question 15.
How do the globulin chains remain tied together in an immunoglobulin G molecule?
Answer:
In an immunoglobulin G molecule the heavy and light chains remain tied together by di-sulphide bonds.

Question 16.
Which type of antibody can penetrate the placental barrier to reach the foetal blood from mother’s body?
Answer:
1gG can penetrate the placental barrier to reach the foetal blood from mother’s body.

Question 17.
Which antibody is present in tears?
Answer:
IgA is present in tears.

Question 18.
Which antibody is synthesised first in human foetus?
Answer:
The antibody synthesised first in human foetus is IgM.

Question 19.
Which antibody protects our body against allergens?
Answer:
IgE protects our body against allergens.

Question 20.
Which is the first line of defence in our immune system?
Answer:
Skin and mucus membrane provide the first line of defence in our body’s immune system.

Question 21.
Which is the second line of defence in our immune system?
Answer:
Phagocytic white blood cells like neutrophils and monocytes provide the second line of defence in our body’s immune system.

Question 22.
Which is the third line of defence of human immune system?
Answer:
Acquired immunity provided by different types of T and B-lymphocytes provides the third line of defence to human immune system.

Question 23.
What is meant by vaccination?
Answer:
Inoculation of the body with vaccines to develop active acquired immunity against specific disease-causing germs or toxins is called vaccination.

Question 24.
What is the full form of DPT vaccine?
Answer:
Full form of DPT is Diphtheria, Pertussis (whooping cough), Tetanus.

Question 25.
What is the full form of TT?
Answer:
Full form of TT is Tetanus Toxoid.

Question 26.
What is the full form of BCG?
Answer:
Full form of BCG is Bacillus CalmetteGuerin.

Question 27.
What is the full form of MMR?
Answer:
Full form of MMR is Mumps, Measles, Rubella.

Question 28.
What is the full form of ATS?
Answer:
Full form of ATS is Anti-Tetanus Serum.

Question 29.
What is the full form of OPV?
Answer:
Full form of OPV is Oral Polio Vaccine.

Question 30.
Give example of attenuated viral vaccines.
Answer:
Vaccines of mumps, measles, rubella, chicken pox belong to attenuated viral vaccines.

Question 31.
What is sub-unit vaccine?
Answer:
The vaccine which is prepared by certain molecular part of a pathogen, a viral protein for instance, is called sub-unit vaccine.

Question 32.
Give example of a sub-unit vaccine.
Answer:
Vaccine of Hepatitis B is a sub-unit vaccine.

Question 33.
To which kingdom of the living world does malaria pathogen belong?
Answer:
Malaria pathogen belongs to kingdom Protista.

Question 34.
What is full form of AIDS?
Answer:
Full form of AIDS is Acquired Immune Deficiency Syndrome.

Question 35.
Which day is observed as World Health Day?
Answer:
Every year 7th April is observed as the World Health Day.

Question 36.
Which day is observed as World AIDS Day?
Answer:
Every year 1st December is observed as the World AIDS Day.

Question 37.
Which disease is commonly known as Lock Jaw disease?
Answer:
Tetanus is commonly known as Lock Jaw disease.

Question 38.
What is the other name of ‘Break Bone fever’?
Answer:
The other name of ‘Break Bone fever’ is dengue.

Question 39.
Which type of hepatitis is transmitted through contaminated food and drink?
Answer:
Hepatitis A is transmitted through contaminated food and drink.

Question 40.
Which vaccine did Calmette and Guerin discover?
Answer:
Calmette and Guerin discovered the vaccine against tuberculosis.

Question 41.
Who discovered the vaccine of polio?
Answer:
Jonas Salk discovered the vaccine of polio.

Question 42.
Who discovered the Oral Polio Vaccine?
Answer:
Albert Sabin discovered the Oral Polio Vaccine.

Question 43.
Name a viral disease which is transmitted by mosquito.
Answer:
Dengue is a viral disease which is transmitted by mosquito.

Question 44.
Mention the full form of ‘WASH’ programme as proposed by UNICEF.
Answer:
The full form of WASH programme isWater and Sanitation Hygiene programme.

Question 45.
Name a virus, which causes severe diarrhoea.
Answer:
Rotavirus causes severe diarrhoea.

Question 46.
Name a bacterial disease, which causes fever, severe chest pain, cough and distressed breathing.
Answer:
Pneumonia causes fever, severe chest pain, cough and distressed breathing.

Question 47.
Name a disease caused by retrovirus.
Answer:
AIDS is caused by retrovirus.

Question 48.
Name two common household disinfectants.
Answer:
Phenyl and bleaching powder are two common household disinfectants.

Question 49.
How can you disinfect your hands without using water?
Answer:
Alcohol-based hand sanitisers can disinfect hands without water.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is immunology?
Answer:
The branch of science, that deals with the study of antigens, antibodies and the overall immune system of the body, is known as immunology.

Question 2.
What is immunity?
Answer:
Immunity is defined as the defence mechanism of the body against a specific infection or toxin or any harmful foreign material, entering the body by the action of specific antibodies or specialised cells or agents.

Question 3.
What is an antigen?
Answer:
Antigens are foreign materials that stimulate the immune system of the body by inducing the synthesis of specific antibodies and sensitising immunologically significant white blood cells.

Question 4.
Mention the characteristic features of antigens.
Answer:
Characteristic features of antigens are as follows-

1. Antigens are commonly proteins, or polysaccharides in nature
2. Antigens are generally of high molecular weight. Minimum molecular weight of an antigen is 10000 Dalton.
3. An antigen induces the synthesis of a specific antibody.

Question 5.
What are the common sources of antigens?
Answer:
The common sources of antigens are as follows-

1. Surface proteins of bacteria and viral capsid are the common sources of antigens.
2. Different toxins, snake venom, sting poisons of bees, wasps, scorpions act as antigens.
3. Secretory or excretory materials of bacteria or parasites contain antigens.
4. Some chemicals, drugs, pollen grains even food materials contain allergic antigens (allergens).

Question 6.
What are exogenous antigens?
Answer:
The antigens, which enter into the body from outside, are called exogenous antigens. Exogenous antigens include different diseasecausing germs, certain allergic food materials, chemicals, pollen grains.

Question 7.
What is endogenous antigen?
Answer:
The antigenic materials, which are synthesised inside the body and are capable of inducing immune response are called endogenous antigens. Certain proteins present on the surface of RBC, cardiolipin of mammalian heart, prostate specific antigen of prostate gland are the examples of endogenous antigens.

Question 8.
What is an antibody?
Answer:
Antibodies are immunoglobulin molecules, which are produced or remain in blood to counteract and inactivate specific antigens and thereby protect the body against their harmful effects.

Question 9.
Mention the characteristic features of antibodies.
Answer:
Characteristic features of antibodies are as follows-

1. Antibodies are glycoproteins commonly called immunoglobulins.
2. Molecular weight of an antibody ranges from 150000 to 950000 Dalton.
3. Antibodies are antigen-specific.

Question 10.
How do antibodies work?
Answer:
Antibodies work through following methods-

1. Antibodies or immunoglobulins bind to specific antigens to agglutinate and precipitate them.
2. Some antibodies bind to antigens to let those to be phagocytized by macrophage cells.
3. Some antibodies immobilize and dissolve antigens.

Question 11.
How many types of antibodies are found in human body?
Answer:
Human body contains five different types of antibodies or immunoglobulins. These are IgA, Ig D, Ig E, Ig G and IgM.

Question 12.
What is primary immune response?
Answer:
The reactions in the body in response to an antigen for the first time is called primary immune response. This response takes a little more time (10-17 days) for recognition of the antigen.

Question 13.
What is secondary immune response?
Answer:
The reactions in response to an antigen, already known to the body’s immune system, is known as secondary immune response. This response is very fast (2-7 days) because memory cells, already produced in the body, recognise the antigen and respond instantaneously.

Question 14.
What is meant by cell-mediated immunity?
Answer:
The immune response, which involves activity of the cytotoxic T-lymphocytes and different phagocytic cells in destroying the pathogens or pathogen infected cells within the body, is called cell-mediated immunity.

Question 15.
What is meant by innate immunity?
Answer:
The innate immunity refers to non-specific defence mechanisms that come into play immediately or within hours of an antigen’s appearance in the body.

Question 16.
What is meant by acquired immunity?
Answer:
The immunity, which develops within the body of an organism by any infection, vaccination or by introduction of antibody artificially, is called acquired immunity.

Question 17.
Schematically represent different types of acquired immunity.
Answer:
Schematic representation of different types of acquired immunity is given below-

Question 18.
What is meant by active acquired immunity?
Answer:
The immunity, which is developed in the body of an organism by introduction of an antigen, naturally or artificially, is called active acquired immunity.

Question 19.
What is artificial active immunity?
Answer:
The active immunity, which develops in an organism after vaccination is called artificial active immunity. Examples-Vaccines like DPT, OPV, BCG etc. develop artificial active immunity.

Question 20.
What is passive acquired immunity?
Answer:
The immunity which is developed in the body of an organism by introduction of an antibody, naturally or artificially, is called passive acquired immunity.

Question 21.
What is natural active immunity?
Answer:
The active immunity, which is developed in an organism after natural infection by any pathogen (virus, bacteria etc.) is known as natural active immunity. Example-After infection of chicken pox, a person develops natural active immunity against this disease and is not attacked by the same disease in future.

Question 22.
What is natural passive immunity?
Answer:
The passive immunity, which is developed by the inflow of antibodies from mother to the foetus through placental circulation is known as natural passive immunity. Example-Immunoglobulin A, acquired by a baby through colostrum of breast milk of the mother, develops natural passive immunity.

Question 23.
What is artificial passive immunity?
Answer:
The passive immunity, which develops in an animal by introduction of antibodies from outside by injection, is known as artificial passive immunity. Example-Antitoxin serum, produced from horse’s blood, is injected to save the life of a person suffering from snake bite.

Question 24.
What is the importance of vaccination?
Answer:
Importance of vaccination are as follows-
1. By means of vaccination specific antibody develops within our body. Memory cells develop in the body, which remain stored in lymphatic system to counter any chance of infection by the same pathogen in future.
2. Certain vaccines develop immunity for lifetime and some others immunize the body for a certain period.

Question 25.
What is meant by attenuated vaccine?
Answer:
The vaccines, which are prepared by living but inactivated pathogens (bacteria or virus) are called attenuated vaccines. Examples-Vaccines of tuberculosis, mumps, influenza, and Oral polio vaccine (Sabin vaccine) belong to attenuated vaccine.

Question 26.
What is meant by killed vaccine?
Answer:
The vaccines, which are prepared with dead or inactivated bacteria or virus, are known as killed vaccines. Examples-Vaccines of typhoid, cholera, whooping cough (pertussis), rabies, hepatitis B and Salk vaccine belong to killed vaccine category.

Question 27.
What is a toxoid?
Answer:
Toxins collected from pathogenic microorganisms, are chemically detoxified keeping their antigenic property intact. These preparations are used as vaccines, which are called toxoids. Examples-Tetanus and diphtheria vaccines are of this type.

Question 28.
What is meant by combination vaccines?
Answer:
Certain vaccines are prepared with different antigens to immunize individuals against more than one disease by a single inoculation. These vaccines are called combination vaccines. Examples-DPT (Diphtheria, Pertussis, Tetanus) vaccine, MMR (Mumps, Measles, Rubella) vaccine are of this type.

Question 29.
What is booster dose of vaccine?
Answer:
To maintain a steady stock of memory cells in the immune system certain vaccines are applied at regular intervals. These slots of vaccines are known as booster dose. Example-Booster dose of tetanus toxoid must be given after every ten years.

Question 30.
Mention the causative agents of diarrhoea. How is the disease transmitted?
Answer:
Causative agents of diarrhoea: Diarrhoea is caused by ETEC- Enterotoxigenic E. coli, Salmonella sp. (bacteria), Rotavirus (virus).
Mode of transmission of diarrhoea: This disease is transmitted through contaminated food and water.

Question 31.
What in meant by primary lymphoid organ?
Answer:
The organs, within which T and B lymphocytes attain maturity, are called primary lymphoid organs. Example-Thymus gland, the site of maturity of T-cells and red bone marrow, the tissue where B-cells mature, are the two primary lymphoid organs.

Question 32.
What is secondary lymphoid organ?
Answer:
Matured T and B-lymphocytes are transferred to some other organs for further proliferation. These organs are known as secondary lymphoid organs. Example-All lymph glands, especially tonsils and spleen are the examples of secondary lymphoid organs.

Question 33.
Write the common symptoms of diarrhoea.
Answer:
Common symptoms of diarrhoea are –

1. frequent watery stool,
2. abdominal pain and cramps,
3. disability to hold bowel movement,
4. nausea and fatigue,
5. thirst and dehydration.

Question 34.
Mention the names of different malaria causing pathogens. How is malaria transmitted?
Answer:
Causative agents of malaria: Malaria is caused by different species of Plasmodium, a parasitic protozoan. They are Plasmodium vivax, P. falciparum, P. malariae and P. ovale.
Transmission of malarial parasite: Female Anopheles mosquito carries Plasmodium from a diseased individual to a healthy person.

Question 35.
Write down the different symptoms of malaria.
Answer:
The symptoms of malaria are-

1. chilled feeling with severe shivering
2. severe headache, [3] very high fever (104 °F or more)
3. remission of fever with profuse sweating
4. fatigue
5. nausea.

Question 38.
Name the causative agent of diphtheria. How is the disease transmitted?
Answer:
Causative agent of diphtheria: Causative agent of diphtheria is a bacterium named Corynebacterium diphtheriae.
Mode of transmission of diphtheria: Diphtheria is transmitted mainly through respiratory droplets. This disease also spread by touching the body of an infected person and from contaminated materials like telephone, utensils, towels, handkerchiefs etc.

Question 37.
Mention the symptoms of diphtheria.
Answer:
The symptoms of diphtheria are-

1. thick, gray coating over pharyngeal wall and tonsils
2. sore throat and hoarseness
3. swelling of lymph glands near the neck
4. distressed breathing and swallowing
5. nasal discharge
6. high fever.

Question 38.
Name the causative agent of pneumonia. How is the disease transmitted?
Answer:
Causative agent of pneumonia: Causative agent of pneumonia is a bacterium named Streptococcus pneumoniae.
Mode of transmission of pneumonia: The pathogens of pneumonia are transmitted through respiratory droplets from the nose and mouth of a sick person.

Question 39.
Mention the symptoms of pneumonia.
Answer:
The symptoms of pneumonia are

1. severe cough
2. distressed breathing
3. chest pain, especially with cough
4. fever
5. breathlessness
6. fatigue.

Question 40.
Name the causative agent of tetanus. How is the disease transmitted?
Answer:
Causative agent of tetanus: Causative agent of tetanus is Clostridium tetani.
Mode of transmission of tetanus: Pathogen of tetanus is transmitted directly from soil through open wounds or injuries. Injuries from contaminated nails, knives, razors, surgical instruments etc. also transmit this disease.

Question 41.
Mention the symptoms of tetanus.
Answer:
The symptoms of tetanus are-

1. fever followed by jaw cramping,
2. spasm in stomach,
3. stiffness of muscles with severe pain,
4. trouble in swallowing,
5. high blood pressure and fast heart rate.

Question 42.
Name the causative agent of tuberculosis. Mention the symptoms of tuberculosis.
Answer:
Causative agent of tuberculosis: Causative agent of tuberculosis is a bacterium named Mycobacterium tuberculosis.
Symptoms of tuberculosis:

1. Night fever with sweating,
2. Dry cough with blood-tinted sputum,
3. Significant weight loss,
4. Fatigue.

Question 43.
How is tuberculosis transmitted?
Answer:
Tuberculosis is transmitted through respiratory droplets from nose and mouth of a diseased person. Exhaled air of the patient carries pathogens of this disease. Inhaling this air from a distance of a few metres, may infect another person with the same disease.

Question 44.
Name the causative agent of dengue. How is dengue transmitted?
Answer:
Causative agent of dengue: Causative agent of dengue is Flavivirus.
Mode of transmission of dengue: Female Aedes aegepti mosquito (which is a blood sucking ectoparasite) carries dengue virus from a diseased person to a healthy individual.

Question 45.
Mention the symptoms of dengue.
Answer:
The symptoms of dengue are-

1. high fever with severe headache
2. pain behind the eyes
3. severe body ache and joint pain
4. rash over skin
5. moderate bleeding from gums.

Question 46.
Name the causative agent of hepatitis A. How is hepatitis A transmitted?
Answer:
Causative agent of hepatitis A: Causative agent of hepatitis A is HAV or Hepatitis A Virus.
Mode of transmission of hepatitis A: This virus comes out through faeces of a person, infected with hepatitis A. The pathogen is then transmitted through contaminated food (raw vegetables) or drinks (water) in a healthy person.
Therefore, in other words it can be stated that this infection is transmitted through faecal-oral route.

Question 47.
Mention the symptoms of hepatitis A.
Answer:
The symptoms of hepatitis A are –

1. nausea and vomiting
2. liver pain
3. loss of appetite
4. darkish urine
5. yellowing of skin and eye.

Question 48.
Name the causative agent of hepatitis B. How is hepatitis B transmitted?
Answer:
Causative agent of hepatitis B: Causative agent of hepatitis B is HBV or Hepatitis B Virus.
Mode of transmission of hepatitis B: This virus is carried by blood or other body fluids. It is transmitted through transfusion of contaminated blood, and sharing same injection needle with a patient. This virus may pass through placenta, therefore, infect a foetus of a diseased mother. It may be transmitted by sexual contact also.

Question 49.
Mention the symptoms of hepatitis B.
Answer:
The symptoms of hepatitis B are-

1. nausea and vomiting,
2. abdominal pain,
3. loss of appetite,
4. darkish urine,
5. yellowing of skin and eye,
6. severe fatigue.

Question 50.
Name the causative agent of AIDS. How is AIDS transmitted?
Answer:
Causative agent of AIDS: The causative agent of AIDS is HIV or Human Immunodeficiency Virus.
Mode of transmission of AIDS: The virus of AIDS is transmitted by transfusion of contaminated blood, sharing same injection needle with a patient, through unsafe sexual contact, from mother to foetus through placental circulation.

Question 51.
Mention the symptoms of AIDS.
Answer:
The symptoms of AIDS are-

1. recurrent fever
2. common cold-like symptoms
3. frequent diarrhoea
4. quick loss of weight
5. swelling of glands in groin
6. fatigue
7. joint pain
8. persistent skin rashes.

Question 52.
What is meant by washing?
Answer:
The process of disinfecting hand and other body parts, garments, utensils, raw food matters, like fish, meat, vegetables and fruits with clean water, soap, detergents or germicidal lotions is known as washing.

Question 53.
Mention the role of different washing materials?
Answer:
The role different washing materials are as follows-

1. Water is used to wash all items.
2. Detergents are used to wash garments, beddings and utensils.
3. Floor cleaners are used to clean floors of room and toilet.
4. Soap, shampoo and shower gels are used in bathing.
5. Hand is washed with soap and disinfecting lotion.

Question 54.
Briefly describe the importance of brushing teeth.
Answer:
Unhygienic oral condition leads to different problems like tooth decay, gum disease, bad breath, pyorrhoea, loosening and falling of teeth. Proper brushing with toothpaste helps in reducing plaque and germ build up in the mouth and reduces the chances of oral problems. For this purpose brushing of teeth is to be done essentially before going to bed.

Question 55.
Why is bathing important for good health?
Answer:
Population of different bacteria, fungi and ectoparasites grow fast on unclean body surface. Sweat and sebum provide the germs a good medium for nutrition and growth. Unclean body surface leads to several skin infections. By regular bathing, these germs are washed off. Therefore, bathing is important to maintain a good health.

Question 56.
What should be the proper bathing technique?
Answer:
To clean the body surface shower with clean water is necessary. Then soap or bathing gel is to be applied and then rubbed with a scrubber to create rich foam. More attention is to be given at the hidden parts like armpits, groins, as these regions provide good places for germ build-up. Finally, the foam is to be cleared with adequate water to get a clean and hygienic skin.

Question 57.
Why are washing and sun drying of garments, beddings, bathing towels, handkerchiefs essential for maintaining hygiene?
Answer:
Pathogens of scabies, ringworm, eczema and a number of allergens spread through contaminated garments, beddings, bathing towels and handkerchiefs. Washing can reduce the population of pathogens from these materials. Therefore, washing and sun drying of these items is essential for maintaining a good hygiene.

Question 58.
Why is washing of hand essential before taking food?
Answer:
We commonly take food by hand. A contaminated hand may carry the pathogens of various diseases like diarrhoea, dysentery, hepatitis A, cholera, gastroenteritis. By washing hand before taking food, the occurrence of these diseases can be reduced to a great extent.

Question 59.
Why an open wound should be washed with germicidal lotion?
Answer:
Skin acts as a great barrier against the entry of germs into our body. However, open wounds become a good entry point for various germs. Therefore, any open wound is to be washed with germicidal lotions to kill the germs in the wound and at its periphery. After washing, the wound must be covered with sterilised bandage, gauge or cotton to resist the entry of germs through it.

Question 60.
What are ‘paratope’ and ‘epitope’?
Answer:
The part of antibody that adheres to antigen is known as ‘paratope’ and the part of the antigen, attached to the paratope is known as ‘epitope.’

Question 61.
What is interferon (IFN)?
Answer:
Interferon is a group of proteins that is formed and released by the host cells in response to pathogens specially virus. These are highly effective in combating hepatitis, influenza etc.

Question 62.
What is MALT?
Answer:
The full form of MALT is Mucosa Associated Lymphoid Tissue. These types of lymphoid tissues are located within the lining of respiratory tract, digestive tract and urino-genital tract and it constitutes 50 % of lymphoid tissues in human body.

Question 63.
What is the main objective of vaccination?
Answer:
Generating memory cells in the blood to recognise a specific antigen for quick triggering of immunological response in case of infection by the same pathogen in future is the main objective of vaccination.

Question 64.
Distinguish between innate and acquired immunity.
Answer:

Features	Innate immunity	Acquired immunity
1. Activation	Becomes active with birth	Becomes active in presence of antigen
2. Specificity	It is nonspecific immune response	It is specific immune response

Question 65.
Distinguish between active acquired immunity and passive acquired immunity.
Answer:

Features	Active acquired immunity	Passive acquired immunity
1. Source of antibody	Originates inside the body with introduction of any antigen	Enters into the body from mother’s body or from other animal source
2. Span of action	Develops slowly but remains active for a long time	Acts instantaneously

Long Questions and Answers : (5 marks for each question)

Question 1.
Briefly describe the structure of the most common antibody present in human plasma. Distinguish between antigen and antibody. 3 + 2
Answer:
Structure of antibody

Immunoglobulin G or IgG is the most common antibody present in human plasma. Its structure is mentioned below.
1. Immunoglobulin G molecule is a ‘Y’ – shaped structure.
2. Each molecule has a specific antigen-binding site, by which it attaches with a specific antigen to inactivate it.
3. The immunoglobulin molecule is composed of 4 polypeptide chains of which two are heavier and two others are lighter in weight. These chains remain attached with di-sulphide bonds.
4. The two forked arms are made up of one light and one heavy chain each. The stem arm of IgG molecule is composed of two heavy chains.

Differences between antigen and antibody

Features	Antigen	Antibody
1. Occurrence	Enters into body from outside (rarely synthesised inside body)	Occurs within the body in the presence of antigen
2. Effect	Causes harm to the body	Protector of the body
3. Chemical nature	Glycoprotein, lipoprotein or polysaccharide	Generally glycoprotein
4. Function	Activates the immune system of the body	Inactivate or destroy antigens

Question 2
Briefly describe the mechanism of immune response against viral attack in human body. Mechanism of immune response against a viral attack
Answer:
Immune response is a complex process involving various cells and biochemical components inside the body.

The steps of immune response against viral antigen are as follows –

1. As any virus reaches blood or attacks any body cells, large phagocytic macrophages engulf those infected cells. Soon viral antigens appear on the cell surface of macrophages.
2. High concentration of viral antigens on macrophage activates helper Tlymphocytes in blood.
3. Helper Tcells immediately initiate the production of cytotoxic killer T-cells, memory T-cells and B-lymphocytes.
4. B-lymphocytes proliferate very fast to produce plasma cells and memory B-cells.
5. Plasma cells produce specific antibodies to bind and inactivate virus before they get chance to infect a cell.
6. Killer Tcells destroy the infected body cells along with viruses.
7. T and memory B- cells stay in the body to recognize the same pathogen in case of further infection and to develop quicker response.

Question 3
What is humoral immunity? How does humoral immunity work?
Answer:
Humoral immunity
The immune response, which involves the action of different B-lymphocytes, like plasma cells, for producing antigen-specific antibodies and memory cells for neutralizing or eliminating toxins and pathogens in the blood and lymph is called humoral immunity.
Mechanism of humoral immunity –
Humoral immunity works for both primary and secondary immune response.
In primary response B-lymphocytes develop typical antibody-producing plasma cells. These cells produce antigen

specific antibodies. Antibodies work in following four ways.

1. Agglutination: By this process antibodies agglutinate pathogens into clusters, which are then collectively phagocytized by macrophages.
2. Precipitation: Some antigen molecules are clamped by antibodies and are precipitated.
3. Opsonisation: Antibodies form a covering on the antigens so that the phagocytic cells ingest packed antigens.
4. Neutralisation: Certain toxic antigens are detoxified and inactivated by the antibodies.

In secondary response memory B-cells play the major role. These cells are produced during primary immune response and remain stored in the secondary lymphoid tissues for keeping the immunological behaviour of the pathogen in memory of the body’s immune system. In case of another attack, these cells help in quick activation of body’s immune system.

Question 4.
Mention the roles of different T-cells in immune response? Mention the roles of different B-cells in immune response? 3 + 2
Answer:
Roles of different T-cells
Different T-cells or T-lymphocytes play different roles in immune response of the body. They are as follows-
1. Cytotoxic T-cells or T_C-cells kill the infected cell, to destroy antigen carrying pathogens within it.
2. Helper T-cells or T_H-cells enhance the activity of killer cells (a type of T_C – cells), antibody producing B-cells and phagocytic macrophages.
3. Suppressor T-cells or T_S-cells destroy T_C-cells, T_H-cells and B-cells to stop immune response after the elimination of the antigens.

Roles of different B-cells :
Different B-cells or B-lymphocytes play different roles in immune response of the body. They are as follows-
1. Plasma cells originated from B-cells produce specific antibodies to inactivate antigens.
2. Memory B-cells remain in lymph glands, keeping the nature of antigens in memory, take quick action in case of any further attack.

Question 5.
Mention the differences between B-cells and T cells.
Answer:
Differences between B-cells and T-cells

Features	B-cells	T-cells
1. Maturation	Lymphoid tissue or bone marrow	Thymus
2. Longivity	Short (few days to a week)	Long (months to years)
3. Surface immunoglobulins	Present	Absent
4. Type of immunity	Humoral immunity	Cell mediated immunity
5. Secretary product	Antibodies	Lymphokines
6. Defence mechanism	Defend against pathogens that enter the blood and lymph	Defend against pathogens that enter the cells
7. Inhibition	Have no inhibitory effect on immune system	Suppressor cells inhibit immune system

Question 6.
Give a brief historical account of the discovery of small pox vaccine.
Answer:
Discovery of small pox vaccine
The scientific concept of vaccination was developed in the later half the of 18th century when a number of scientists and physicians were working hard to develop a vaccine against small pox, the most deadly and contagious disease of that time. Scientists noticed that most individuals, who once suffered from cow pox safely bypassed small pox. But the search was on for long 25 years. Then Dr. Edward Jenner (1798) broke through the concept of vaccination. He collected a little pus from a cow pox vesicle on the hand of Sarah Nelmes, a milkmaid, and introduced it into the arm of James Phipps, an eight year old boy.

After two months, the boy was inoculated with small pox virus, but he did not develop the disease. The modern concept of vaccination is standing on this story. After this discovery, the practice of vaccination took the correct route. After a long battle for about two centuries, small pox has now been eradicated from the world.

Question 7.
What is a vaccine? Mention the basic working principles of vaccines to develop immunity in the body. 2 + 3
Answer:
Vaccine
Vaccine is an antigenic material that is prepared with killed or weakened pathogens, part of pathogens, bacterial toxins or microbial proteins, which do not cause illness but provide active acquired immunity against those pathogens when introduced into the body.

Working principle of vaccines
By vaccination, a killed germ, attenuated (weakened) germ, toxoids (toxins collected from germs) or subunits (fragments of proteins from germs) are introduced into the body of an individual. These may be injected or administered orally. As soon as the substance enters the body, antigens present in it, activate the immune system and initiate an immune response. T-cells and B-cells take a little time to inactivate such little quantity of antigens and this process is known as primary immune response.

However, in this case, main function is done by memory B-cells. These cells, produced during the immune response, are retained in lymph nodes such as spleen, thymus etc.. for a long time. In case of any future infection by the same germ, these memory cells recognize those antigens instantly and inactivate or destroy the attacker very fast. This process is recognized as secondary immune response. Thus, a successful vaccination immunizes a person effectively.

Question 8.
Give a brief account of different types of vaccines.
Answer:
Types of vaccines

With the development of science, new and advanced varieties of vaccines are being developed. Till date World Health Organisation (WHO) has licensed vaccines for 25 diseases. Different types of vaccines are:
1. Killed vaccine: These vaccines contain killed pathogens. Vaccines of cholera, plague, influenza are of this type.

2. Live attenuated vaccine: By some laboratory techniques virulence of the pathogens are reduced to prepare this type of vaccines. Vaccines of mumps, measles, and rubella are of this type.

3. Toxoid vaccine: This type of vaccine is prepared by inactivated toxins from pathogens. Vaccines of tetanus, diphtheria are of this type.

4. Conjugate vaccine: Generally polysaccharide of bacterial capsule is attached with a protein to prepare this vaccine. Body’s immune system can recognise this conjugated protein and keep it in memory for future immune response. Vaccine against Haemophilus influenzae type-B is of this type.

5. Sub-unit vaccine: This type of vaccine is prepared by small fragments of pathogenic protein. Vaccine against Hepatitis B is of this type.
Heterotypic vaccine: This is prepared by pathogens, causing disease to other animals but less or non-virulent to human. Vaccines of small pox and tuberculosis are of this kind.

Question 9.
Why and when should an individual wash hands? Write down the proper method of washing hand. 1 + 2 + 2
Answer:
Reason of washing hand
We take food with hand. We often touch our lips, face and nose with our hands. By contaminated hands, germs or toxins may enter our body through mouth, eyes and nose. Therefore, one must wash the hands to stay healthy.

Time of washing hand
Hands must be washed before –

1. taking food
2. cooking
3. serving food
4. feeding and attending a baby or a patient.

Proper washing of hand is a must after using toilet, cleaning raw vegetables, fish and meat, attending a patient, sweeping and cleaning rooms and toilets, polishing shoe and tying shoe-laces, checking air pressure of cycle tyre, coming home from outside, etc.

Proper method of washing hand :
Proper method of washing hand is mentioned below.

1. Wet the hands with clean water.
2. Take liquid hand-wash or soap in wet hands and rub it for one or two minutes to make rich foam.
3. Carefully rub in between all fingers.
4. Place the hands under running water and continue rubbing until the foam clears.
5. Close tap with clean cloth and wipe the hand with dry and clean towel.

Question 10.
Wilte a short note on ‘WASH’ programme of UNICEF.
Answer:
‘WASH’ programme of UNICEF
Percentage of healthy children in a population is the index of development of a nation. But it is unfortunate that even in the 21 st century, millions of children suffer from diarrhoea and several other water-borne diseases. This happens because of contaminated water, which occurs mostly due to lack of proper sanitation. 44 % of global population defecate in open areas. Faeces contain numerous germs, which easily contaminate water, especially during rainy season.

In view of that, UNICEF (United Nations International Children’s Emergency Fund) has developed a global strategy to lift the standard of health of school children by providing them adequate drinking water, infrastructure for proper sanitation and sense of hygiene. This programme is popularly known as ‘WASH’ (Water Sanitation Hygiene programme). United Nations has set a goal for sustainable development of the standard of living of world population in this millennium. To reach the target, UNICEF has developed a strategy to maximise child survival rate by providing an access to adequate drinking water, sanitation facilities to schools all over the world along with education and nutrition

Question 11.
Describe the WASH strategy taken by UNICEF to improve hygiene behaviour among school children. How can the WASH programme be made successful? 3 + 2
Answer:

WASH strategy to improve hygiene behaviour among school children Schools are the places where a child spends most of the time of his or her life all through the development period. So UNICEF has developed the plan to make every school a child-friendly place. In view of that UNICEF has extended both monetary and strategic support to all developing countries of the world to develop infrastructure for child-friendly schools. The strategy to enhance child survival and development, UNICEF has encouraged a three pillar approach. The first is enabling a child-friendly environment in the school. Next is to improve hygiene behaviour among the students and the third one is to build infrastructure for water supply and sanitation services.

Points to make WASH successful :
The points to make WASH successful are as follows-

1. Wash your hands with adequate water and soap before taking food and after using toilets.
2. Always use sanitary toilets.
3. Clean raw fruits and vegetables before consuming.
4. Keep a close vigilance on drinking water sources to reduce contamination to zero.
5. Clean water storage containers every day.
6. Keep your domestic and school toilets clean.
7. Clip your nails regularly and do not let any filth to deposit under it.

Question 12.
Mention different hygienic practices to secure good health of a person as well as of the society.
Answer:
Different types of hygienic practices
The conditions or practices helpful to maintain health and to prevent diseases, especially through cleanliness are known as hygiene. Hygiene can be practiced in three different levels, i.e., personal, household and social levels, which are mentioned below.
1. Personal level hygiene:

• Cleaning hands before taking food, after using toilet and handing any unclean material.
• Brushing teeth after taking meal and before going to bed.
• Taking bath once or twice a day.
• Trimming hair and clipping nails regularly.

2. Househoid level hygiene:

• Washing and sun-drying clothing and bedding at regular intervals.
• Cleaning utensils, kitchen equipment, raw vegetables, fish and meat.
• Cleaning toilet, basins and sinks.
• Cleaning and disinfecting water reservoirs.

3. Social level hygiene:

• Cleaning of sewage system at regular interval.
• Maintaining general cleanliness in hospitals, educational institutions, market places, railway stations, bus terminus,
• auditoriums, theaters and other community places.
• Regular cleaning and disinfecting public toilets.