Question

Which of the following immunogens is most likely to promote effective T:B cell collaboration?

A) Pathogens with a high mutation rate
B) Large, highly repetitive antigens
C) Small, non-repetitive antigens
D) Antigens with no MHC-binding capacity

Answer 1

Large, highly repetitive antigens are most likely to promote effective T:B cell collaboration as they can activate B cells and with the presence of T cell cytokines, further potentiate the immune response.

Step-by-step explanation:

The most likely immunogen to promote effective T:B cell collaboration is B) Large, highly repetitive antigens. These antigens can crosslink the B cell receptor (BCR) due to their repetitive nature, leading to B cell activation even without T cell help. However, the presence of helper T cells will further enhance the immune response. As per Figure 21.25., to actuate fully, a B cell requires signals from both the native antigen and the T cell's cytokines. The T cell-dependent antigen needs to be presented on a class II MHC molecule, which the B cells process and present to helper T cells (Th2 cells). The T cell receptor (TCR) of a helper T cell binds to antigens presented with MHC II molecules. Once activated, these T cells secrete cytokines that are instrumental for B cell activation and antibody production.

Pathogens with a high mutation rate (A) might evade immune detection, small and non-repetitive antigens (C) may not effectively crosslink BCRs, and antigens with no MHC-binding capacity (D) cannot be presented to T cells effectively, leading to a diminished immune response.