Choose the correct statements about antibodies and acquired immunity:
A. An antibody molecule, having two light chains and two heavy chains, is represented as H2L2.
B. Because antibodies are found in the blood, the antibody-mediated response is also called humoral immune response.
C. The cell-mediated immune response is mediated by the B-lymphocytes.
D. The colostrum secreted by the mother during the initial days of lactation has abundant antibodies of the IgG type.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A and B only
Acquired immunity works in two ways. In the antibody-mediated (humoral) response, B-lymphocytes produce antibodies into the blood. In the cell-mediated response, T-lymphocytes act directly. Ready-made antibodies can also reach an infant from the mother, which is passive immunity.
Statement A: An antibody molecule, having two light chains and two heavy chains, is represented as H2L2. — True. Each antibody molecule has four peptide chains: two small light chains and two longer heavy chains. Hence it is written as H2L2.
Statement B: Because antibodies are found in the blood, the antibody-mediated response is also called humoral immune response. — True. Blood is one of the body fluids (humors), and the antibodies of this response are found in it. So it is called the humoral immune response.
Statement C: The cell-mediated immune response is mediated by the B-lymphocytes. — False. Cell-mediated immunity (CMI) is mediated by the T-lymphocytes. B-lymphocytes produce antibodies, which belong to the humoral response.
Statement D: The colostrum secreted by the mother during the initial days of lactation has abundant antibodies of the IgG type. — False. Colostrum has abundant antibodies of the IgA type, which protect the infant. This is an example of passive immunity.
NCERT Extract:
Acquired Immunity – “… Each antibody molecule has four peptide chains, two small called light chains and two longer called heavy chains. Hence, an antibody is represented as H2L2. Different types of antibodies are produced in our body. IgA, IgM, IgE, IgG are some of them. A cartoon of an antibody is given in Figure 7.4. Because these antibodies are found in the blood, the response is also called as humoral immune response. This is one of the two types of our acquired immune response – antibody mediated. The second type is called cell-mediated immune response or cell-mediated immunity (CMI). The T-lymphocytes mediate CMI.”
Active and Passive Immunity – “… The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant.”
Figure 7.4 Structure of an antibody molecule