In the immune system, what is the role of antigen-presenting cells when interacting with MHC II?

Antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells, have a crucial role in initiating immune responses by presenting foreign antigens to T cells. When APCs interact with Major Histocompatibility Complex (MHC) class II molecules, they display processed fragments of extracellular proteins (antigens) on their surface. This presentation is essential for the activation of helper T cells, which recognize the antigen-MHC II complex through their T cell receptors (TCRs).

Once activated, helper T cells proliferate and differentiate into various subtypes, which then coordinate the immune response by releasing cytokines. These cytokines stimulate other immune cells, such as B cells and cytotoxic T cells, to respond effectively to pathogens. Thus, the relationship between APCs and MHC II is fundamental in linking the innate and adaptive immune responses, allowing for a tailored attack against specific foreign invaders.

The other choices do not accurately describe the primary role of antigen-presenting cells in the context of MHC II interaction. While APCs are involved in facilitating the elimination of pathogens and can produce antibodies (with B cells), their distinct function regarding MHC II is specifically to present antigens to helper T cells. They do