Class 12 - Biology - Understanding Immunity (Q & A) - Chapter: Human Health and Diseases (#class12Biology)(#cbsenotes)(#eduvictors)(#immunity)

Class 12 - Biology - Understanding Immunity (Q & A) - Chapter: Human Health and Diseases

Q1: Define immunity.

Answer: Immunity means resistance to infections and antigens. Immunity is the capacity of an organism to resist or defend itself from the development of a disease.

Q2: What is an antigen? Give some examples.

Answer: Any substance or molecule that induces the immune system to produce antibodies against it is called an antigen.  Examples include pathogens, virus, pollens, chemicals etc.

Q3: Name two main types of immunities.

Answer: 

1. Innate immunity

2. Acquired immunity

Q4: What is innate immunity?

Answer: Innate immunity is inherited by the organism from the parents and present at the time of birth.

Q5: Explain the four types barriers of innate immunity.

Answer: Innate immunity consists of four types of barriers :

(a) Physical Barriers: prevent entry of microorganisms in the body e.g. skin, mucus coating of epithelium of respiratory, gastrointestinal and urinogenital tracts.

(b) Physiological Barriers: prevent microbial growth in the body. e.g. acid of stomach, lysozymes of saliva and tears

(c) Cellular Barriers: are phagocytes and destroy microbes e.g. PMNL, monocytes, neutrophils and macrophases

(d) Cytokine barriers : are virus infected cells secrete proteins called interferons which protect non-infected cells from further infection.

Q6: What is an acquired immunity? List its important features.

Answer: Acquired immunity is not present since birth. It is developed during individual's lifetime.

(i) It is pathogen specific and is characterised by memory,

(ii) When it encounters a pathogen for the first time, it produces a response called primary response, which is of low intensity,

(iii) Further encounter with same pathogen produces highly intensified secondary or anamnestic response due to memory of the first encounter.

(iv) Immune responses are produced by lymphocytes (B-cells and T-cells)

Q7: Based on defense mechanism, how acquired immunity is classified?

Answer: Two types of acquired immunity:

(a) Humoral immune response or Antibody Mediated Immunity (AMI) 

It is mediated by antibodies present in blood and lymph.

(b) Cell-mediated immune response or Cell Mediated Immunity (CMI) 

It is mediated by T-lymphocytes. The graft rejection during organ transplantation, because of the ability to differentiate between self and non-self, is due to the cell-mediated immunity.

Q8: What are antibodies? 

Answer: Antibodies are immunoglobulin protein molecules (Ig). These are protective proteins produced by the immune system in response to the presence of a foreign substance. There are of five types of antibodies:  IgG, IgM, IgA, IgD, IgE

Q9: Draw the structure of an antibody molecule.

Answer: Each antibody molecule has four peptide chains, i.e. two small called light (L) chains and two longer called heavy (H) chains. Hence, an antibody is represented as H^.

Q10: Tabulate four differences between active immunity and passive immunity.

Answer: 

Active Immunity	Passive Immunity
1. Body prepares antibody itself due to exposure of antigen (Pathogen). Example : Typhoid vaccination	1. Preformed antibodies are injected in the body in case of deadly microbe attack. Example : Anti-snake venom, ATS.
2. Immunity is not immediate	2. Very quick immune response.
3. It has very few side effects.	3. May show side effects like allergic reaction.
4. It lasts for long period.	4. It lasts for limited period.

Q11: What is the working principle of vaccination or immunisation?

Answer: Immunity is obtained after an infection, but immunity can also be achieved artificially by vaccination (also called immunization). The principle is based on the property of memory of| immune system.

① Vaccination is the process of introduction of weakened or inactivated pathogens or proteins (vaccine) into a person to provide protection against a disease.

② Immunisation is a process by which the body produces antibodies against the vaccine (primary response) and develop the ability to neutralise pathogens during actual infection (secondary response), i.e. the body become immune to that antigen or infection.

③ Vaccine generates memory B and T-cells that recognise the pathogens on subsequent exposure and produce an intense immune response.

⑤ In case of requirement of quick immune response like tetanus infection, preformed antibodies are injected into the patient. This is called passive immunisation.

④ Recombinant DNA technology has produced antigenic polypeptides of pathogen in bacteria or yeast. This allowed large scale production of vaccine, e.g. hepatitis-B vaccine from yeast, etc.

Q12: What is auto immunity?

Answer: When the immune system of body starts destroying ‘self” cells and molecules, called auto immune diseases e.g. Rheumatoid arthritis, multiple sclerosis and insulin-dependent diabetes.

Q13: Define allergy.

Answer: Allergy is an exaggerated response of immune system to certain antigens present in the environment.

Q14: What are the symptoms of allergy?

Answer: Sneezing, watery eyes, rashes, running nose and difficulty in breathing.

Q15: How does allergy develop?

Answer: The first exposure to an allergen causes sensitization. Subsequent exposures to the same allergen produce allergy symptoms. On exposure to allergens like dust, pollens, etc., chemicals like histamine and serotonin are released from the mast cells, resulting in an allergic response.

Q16: What are allergens?

Answer: Allergens are the substances to which immune system shows exaggerated response. e.g. mites in dust, pollens, animal dander, perfume, wool, nail polish and drugs.

Q17: Give an example of a plant which came into India as a contaminant and is a cause of pollen allergy.

Answer: Parthenium or Carrot grass.

Parthenium, which is a noxious weed, came to India as a contaminant with imported wheat and caused pollen allergy.

Q18: Where do the lymphocytes produced by the lymphoid organ mentioned above migrate and how do they affect immunity?

Answer: The lymphocytes produced migrate to secondary lymphoid organs like spleen, lymph nodes, etc. They trap the microorganism thereby activating the lymphocytes present in the lymph nodes and produce an immune response affecting the immunity.

Q19: Expand the name of the enzyme ADA. Why is this enzyme essential in the human body? Suggest a gene therapy for its deficiency.

Answer: ADA–Adenosine deaminase.

This enzyme is essential for immune system to function. ADA deficiency can be cured by gene therapy. Lymphocytes from the blood of the patients are extracted and cultured outside the body. A functional ADA cDNA (using a retroviral vector) is introduced into these lymphocytes and these lymphocytes are then returned to the patient's body.  However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes.

Q20: What is the difference between primary immune response and secondary immune response?

Answer: When our body encounters a pathogen for the first time produces primary response.

Subsequent encounter with the same pathogen generates highly intensified secondary response.

Q21: Name the category of the disease Rheumatoid arthritis.

Answer: Auto-immune disease.

👉See Also:

The Living World (AIPMT 7 MCQs)
Kingdom Fungi (AIPMT MCQs)
Plant Nutrition MCQs (AIPMT/NEET)
Plants Of Special Interests (Pre-Medical)

Environmental Biology MCQs (AIPMT/NEET)
Genetics MCQs (AIPMPT/NEET)
Evolution (Very Short Question Answers)
Famous Indian Biologists
Animal Nutrition and Digestive System (AIPMT MCQs)
Human Nutrition (Worksheet)
Five Digestive Juices
List of Important Proteins
Human Reproduction (Important Terms)
Human Reproduction System (Very Short Q & A)
HIV/AIDS (A Brief Introduction)
AIPMT/NEET Biology Quiz-1
An overview of Virus and Viroids (Q & A)