Question

The co-stimulatory molecule _____ on professional antigen-presenting cells binds _____ on the surface of naive T cells.

1) DC-SIGN; ICAM-3
2) B7; CD28
3) ICAM-1; LFA-1
4) MHC class II; T-cell receptor
5) MHC class II; CD4

Answer 1

The co-stimulatory molecule B7 on APCs binds CD28 on naive T cells, which is essential for T cell activation and proper immune response.

Step-by-step explanation:

The co-stimulatory molecule B7 on professional antigen-presenting cells binds CD28 on the surface of naive T cells. The correct answer to the question is option 2) B7; CD28.

Professional antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells, present antigens via major histocompatibility complex (MHC) molecules to T cells. The interaction is not just limited to the MHC molecule and the T cell receptor (TCR); another crucial interaction occurs through the co-stimulatory molecule B7 on APCs and the CD28 receptor on T cells.

This engagement is imperative for T cell activation, proliferation, and survival, ensuring that naive T cells become effector T cells capable of responding adequately to a pathogen. Without this co-stimulatory signal, T cells may become anergic, meaning they won't respond to antigenic stimulation.