Question

What is the committing step for helper T cell activation?

a) The release of interleukin-1 (IL-1)
b) The simultaneous expression of the high affinity IL-2 receptor subunit CD25 and the release of IL-2
c) Phagocytosis of the antigen
d) Interaction with cytotoxic T cells
e) Activation of the alternative complement pathway

Answer 1

The committing step for helper T cell activation occurs when a CD4+ helper T cell binds the MHC II-antigen complex on an APC, with the concurrent expression of CD25 and release of IL-2 being the key event.

Step-by-step explanation:

The committing step for helper T cell activation is when a CD4+ helper T cell binds the MHC II-antigen complex on an antigen-presenting cell (APC), leading to the release of cytokines from both the APC and the T cell. This interaction is pivotal for the activation and initiation of the immune response. The correct answer to the student's question is b) The simultaneous expression of the high affinity IL-2 receptor subunit CD25 and the release of IL-2, which are part of the cytokine signaling essential for the proliferation and differentiation of activated T cells.