Statement I : Antibodies are protein molecules, each of which has four light chains .

Statement II : Rejection of a kidney graft is the function of B-lymphocytes

Both statement I and statement II are incorrect.

The correct answer is Option (4) – Both statement I and statement II are incorrect.

Statement I :

Antibodies are protein molecules that consist of four polypeptide chains, but they do not have four light chains. Antibodies have a Y-shaped structure composed of two identical heavy chains and two identical light chains.

Each antibody molecule has two heavy chains and two light chains, resulting in a total of four chains. The heavy chains are larger and have a more complex structure, while the light chains are smaller. The light chains are connected to the heavy chains by disulfide bonds, forming the overall antibody structure.

The combination of heavy chains and light chains gives antibodies their diversity and specificity in recognizing and binding to specific antigens. The variable regions of the heavy and light chains form the antigen-binding site, allowing antibodies to interact with and neutralize antigens.

In summary, antibodies consist of two heavy chains and two light chains, resulting in a total of four chains in each antibody molecule.

Statement II :

"Rejection of a kidney graft is the function of B-lymphocytes" is not accurate. B-lymphocytes do not play a direct role in the rejection of a kidney graft.

In the context of organ transplantation, the rejection of a kidney graft typically involves the immune response mediated by T-lymphocytes rather than B-lymphocytes. T-lymphocytes, specifically the cytotoxic T-cells, recognize and attack the transplanted organ as foreign, leading to graft rejection.

During a kidney transplant, the recipient's immune system recognizes the transplanted kidney as non-self due to the differences in human leukocyte antigens (HLA) between the donor and recipient. This triggers an immune response aimed at eliminating the perceived threat. The immune response involves the activation and proliferation of T-lymphocytes, which play a central role in orchestrating the rejection process.

B-lymphocytes, on the other hand, primarily function in the humoral immune response by producing antibodies. They are responsible for the production of antibodies that specifically target foreign antigens. While B-lymphocytes can be involved in the overall immune response during organ transplantation, their role is not primarily associated with the direct rejection of the kidney graft.

In summary, the rejection of a kidney graft is mainly mediated by T-lymphocytes, particularly cytotoxic T-cells, rather than B-lymphocytes.