Class 12 Biology MCQ – Human Health – Immune System in the Body


This set of Class 12 Biology Chapter 8 Multiple Choice Questions & Answers (MCQs) focuses on “Human Health – Immune System in the Body”.

1. What is the life span of the memory B-cells of the immune system?
a) A few days
b) A few hours
c) A few years
d) A few years to whole life
View Answer

Answer: d
Explanation: The life span of the memory B-cells of the immune system is a few years to whole life. These memory cells do not produce antibodies but when the same pathogen attacks for the second time, that differentiate into effector cells.

2. Which of the following is introduced during smallpox vaccination?
a) Antibodies
b) Antigens
c) Attenuated virus
d) WBCs
View Answer

Answer: c
Explanation: Small Pox vaccination is a first-generation vaccine where an attenuated form of the virus is injected into the body of the patient. The first vaccination was developed by Edward Jenner against smallpox.

3. Primary response of the body to an antigen is much stronger and intense that the Secondary response.
a) True
b) False
View Answer

Answer: b
Explanation: Primary immune response is the first immune response developed during the first encounter with the antigen. It is feeble but relatively longer. The secondary immune response is a quick heightened immune response against a subsequent encounter with the same antigen. It is due to the presence of memory cells against that antigen. Hence, the secondary response is more intense than the primary response.
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4. Formation of a large number of effector cells against a particular antigen is called ______
a) Mass replication
b) Clonal selection
c) Mass selection
d) Pure line selection
View Answer

Answer: b
Explanation: Formation of a large number of effector cells against a particular antigen is called Clonal selection. It involves the formation of a clone of cells by each activated T-lymphocyte and antibody-producing plasma cells by activated B-lymphocyte, each exhibiting the specificity for the same antigen.

5. Which of the following immunoglobulins is also called secretory immunoglobulin?
a) IgG
b) IgA
c) IgM
d) IgE
View Answer

Answer: b
Explanation: IgA immunoglobulins are also called secretory immunoglobulin because it is present in all the body secretions including colostrum and mother’s milk. It functions as the first line of defence against ingested and inhaled pathogens by activating alternative pathways of the complement system.
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6. Which of the following is an immunosuppressant drug?
a) Antihistamine
b) Cyclosporin
c) Neomycin
d) Streptokinase
View Answer

Answer: b
Explanation: Cyclosporin is an immunosuppressant drug. This drug prevents rejection of kidney, heart and liver transplants. It destroys T-cell mediated immune responses while spares humoral antibody responses.

7. Which one of the following people are given the highest priority in transplanting organs to a donor?
a) Identical twin
b) Sibling
c) Parent
d) Unrelated donor
View Answer

Answer: a
Explanation: For organ or tissue transplantation, the preference order for the donor is Identical twin > Sibling > Parent > Unrelated Donor. As there are antigens which are likely to be attacked by recipient T-cells and antibodies, the recipients of organ or tissue transplants are always given immunosuppressants.

8. Immunosuppressants are chemicals which enhance the immune system of the body.
a) True
b) False
View Answer

Answer: b
Explanation: Immunosuppressants are chemicals which suppress the immune reaction of the body so that the antigens of the patient’s body do not attack the transplanted organs or tissues.

9. What is the full form of SCID?
a) Severe Combined Immunodeficiency
b) Sarcolemma Infected Disease
c) Septic Infectious diseases
d) Seven Convoluted Immunity disorder
View Answer

Answer: a
Explanation: SCID stands for Severe Combined Immunodeficiency where very few T-lymphocytes are formed. B-lymphocytes are also deficient. As a result, the patient dies of even minor infections.

10. Which of the following is not a cause of Immunodeficiency diseases?
a) Gene mutation
b) Infection
c) Accident
d) Shortage of water in the body
View Answer

Answer: d
Explanation: Immunodeficiency diseases are disorders of the immune system where one or more components of innate or acquired immunity become defective due to gene mutations, Infections, Malnutrition or eve accidents.

11. Lymphoid Organs are not responsible for ___________
a) Proliferation of lymphocytes
b) Differentiation of lymphocytes
c) Destruction of lymphocytes
d) Maturation of lymphocytes
View Answer

Answer: c
Explanation: Lymphoid organs are not responsible for the destruction of lymphocytes. Lymphoid organs are those organs having lymphatic tissues where maturation, proliferation and differentiation of lymphocytes occur.

12. In which of the following places MALT is not found?
a) Respiratory tract
b) Digestive tract
c) Urogenital tract
d) Eyes
View Answer

Answer: d
Explanation: MALT is not found in the eyes. MALT is a lymphoid tissue which is located within the mucosal lining of the major tracts like respiratory, digestive and urogenital tracts.

13. MALT constitutes for about _______ percentage of the lymphoid tissue in the human body.
a) 30%
b) 40%
c) 50%
d) 60%
View Answer

Answer: c
Explanation: MALT stands for Mucosal Associated Lymphoid Tissue. It constitutes about 50% of the lymphoid tissue in the human body.

14. Which of the following organs is also called as “Graveyard of RBCs”?
a) Spleen
b) Heart
c) Bone Marrow
d) Liver
View Answer

Answer: a
Explanation: Spleen is also called as Graveyard of RBCs. It is a large bean-shaped organ which mainly contains lymphocytes, phagocytes and a large number of erythrocytes. It acts as a filter of blood by trapping blood-borne microorganisms.

15. Which of the following organ is also called as “Throne of Immunity”?
a) Bone Marrow
b) Thymus
c) Brain
d) Heart
View Answer

Answer: b
Explanation: Thymus is also called as Throne of Immunity or training school of T-lymphocytes. It is a lobed organ located near the heart and beneath the breast bone. It is the site where T-lymphocytes mature.

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