MHC class II molecules play a crucial role in the immune system by presenting antigens specifically to CD4+ T helper cells. This interaction is fundamental for the activation of these T cells, which are essential for orchestrating various adaptive immune responses.
When antigen-presenting cells, such as B cells, dendritic cells, and macrophages, engulf pathogens, they process these antigens and present them on their surface bound to MHC class II molecules. This presentation is critical because CD4+ T cells recognize these antigen-MHC class II complexes through their T-cell receptors (TCRs). This recognition is the first step in the activation of CD4+ T cells, leading to their proliferation and differentiation into various subsets that help coordinate the immune response, including the activation of B cells and cytotoxic T cells.
The other options do not align with the primary role of MHC class II molecules. For instance, MHC class I molecules are responsible for presenting peptides to CD8+ T cells, which is a separate function from that of MHC class II. Additionally, while regulatory T cells do play a role in modulating the immune response, they do not specifically interact with MHC class II for their primary function. Lastly, binding to antiviral antibodies