Question

Activation of resting B cells by T helper cells depends directly upon costimulatory interaction between?

1) B7 and CD28
2) B7 and CTLA-4
3) CD4 and MHCI
4) CD40 and CD40L
5) ICAM-1 and LFA-1

Answer 1

Activation of resting B cells by T helper cells requires costimulatory interaction between CD40 on B cells and CD40L on T helper cells, necessary for full B cell activation, proliferation, and differentiation.

Step-by-step explanation:

The activation of resting B cells by T helper cells indeed depends directly upon a costimulatory interaction. Among the options provided, the correct interaction for the costimulatory process is between CD40 on the B cell and CD40L (CD40 ligand) on the T helper cell. When a B cell has processed an antigen, it presents parts of this antigen on its surface in complex with MHC II molecules. The helper T cell, with its T cell receptor (TCR) and CD4 molecule, recognizes this antigen-MHC II complex. However, for full activation of the B cell, a second signal is required which is provided by the interaction of CD40 on the B cell with CD40L on the T helper cell. This costimulatory signal, along with the cytokines released from the helper T cell, stimulates the B cell to proliferate and differentiate into memory B cells or antibody-producing plasma cells.