Question

Binding of _____ to _____ induces T-cell proliferation and differentiation of T cells.

a. B7 ; MHC class II
b. CD28 ; TCR along with CD3 complex and zeta chains
c. LFA-1 ; ICAM-I
d. IL-2 ; the high-affinity IL-2 receptor
e. IL-2 ; the low-affinity IL-2 receptor

Answer 1

The correct answer is 'd. IL-2 ; the high-affinity IL-2 receptor'. IL-2 binding to its high-affinity receptor on T cells is vital for their proliferation and differentiation.

Step-by-step explanation:

Binding of IL-2 to the high-affinity IL-2 receptor induces the proliferation and differentiation of T cells. When a T cell becomes activated after recognizing an antigen presented in association with an MHC molecule on an antigen-presenting cell (APC), it starts to express the high-affinity IL-2 receptor. Once IL-2 binds to this receptor, it triggers signaling pathways that lead to T cell proliferation and differentiation into effector cells capable of executing the immune response.

The process of T cell activation involves multiple steps. Initially, a T cell receptor (TCR) recognizes a processed antigen presented by MHC molecules on APCs. Specifically, helper T cells bind antigens presented with MHC II molecules. After this antigen recognition, several co-stimulatory signals are also required, one of which is the interaction between CD28 on the T cell and B7 on the APC. Following activation, T cells increase the expression of the high-affinity IL-2 receptor, allowing them to respond to IL-2, which is a crucial growth factor for T cells. This interaction is fundamental in enhancing the immune response by facilitating the clonal expansion of T cells.