Question

The T cell ligand binding B7 on a professional Antigen-presenting cell is:

1) CD2
2) CD28
3) LFA-1
4) ICAM-1
5) VCAM-1

Answer 1

The T cell ligand that binds to B7 on a professional Antigen-presenting cell is CD28, necessary for the activation of T cells through a necessary co-stimulatory signal.

Step-by-step explanation:

The T cell ligand that binds B7 on a professional Antigen-presenting cell (APC) is CD28. This is a crucial interaction in the immune response, necessary for the activation of T cells. The B7 molecule is expressed on professional APCs like dendritic cells, macrophages, and B cells. Importantly, T cells require two signals for activation: the recognition of the antigen-MHC complex by the T cell receptor (TCR), and a co-stimulatory signal provided by the interaction of CD28 on

T cells with B7 on APCs. Failure to receive the second co-stimulatory signal can lead to T cell anergy or apoptosis, making this interaction essential for a proper immune response. Other molecules listed such as CD2, LFA-1, ICAM-1, and VCAM-1 play different roles in the immune response and cell-cell adhesion, but do not bind B7. The T cell ligand that binds B7 on a professional Antigen-presenting cell is CD28, which is crucial for T cell activation.