Question

Males with a deficiency in the CD40 ligand:

a. can make IgM in response to T-cell independent antigens.
b. suffer from hyper-IgM syndrome.
c. can make antibodies to T-cell dependent antigens.
d. A & B
e. A, B & C

Answer 1

Males with a deficiency in the CD40 ligand can produce IgM in response to T-cell independent antigens but suffer from hyper-IgM syndrome, which prevents them from making antibodies to T-cell dependent antigens.

Step-by-step explanation:

Males with a deficiency in the CD40 ligand can indeed make IgM in response to T-cell independent antigens. This is because T cell-independent activation of B cells involves the crosslinkage of B-cell receptors (BCRs) by repetitive non-protein antigen epitopes, leading to the production of IgM by plasma cells without the need for T cell help.

Additionally, these individuals suffer from hyper-IgM syndrome, a condition characterized by an inability to undergo class switch recombination due to a lack of functional CD40 ligand interactions with CD40 on B cells, preventing the switch from IgM to other immunoglobulin isotypes like IgG, IgA, or IgE during responses to T cell-dependent antigens.

As a result of CD40 ligand deficiency, these males cannot make antibodies to T cell-dependent antigens because the process requires cooperation between helper T cells and B cells.