What immune cell type binds to MHC class II molecules?

The immune cell type that binds to MHC class II molecules is CD4+ T cells. MHC class II molecules are primarily present on professional antigen-presenting cells, such as dendritic cells, macrophages, and B cells. These molecules present processed antigens to CD4+ T cells, which are crucial for the adaptive immune response.

When a CD4+ T cell binds to an MHC class II molecule that is displaying a peptide, it initiates a series of immune responses, including the activation of B cells for antibody production and the enhancement of the cytotoxic capabilities of CD8+ T cells. This interaction is essential for orchestrating a coordinated response to pathogens, particularly extracellular ones.

The other immune cell types mentioned, such as CD8+ T cells and natural killer cells, primarily interact with MHC class I molecules, which present intracellular antigens. B cells are important in the immune response but do not directly bind to MHC class II molecules in the same manner as CD4+ T cells; rather, they can present antigens to helper T cells via their B cell receptors in conjunction with MHC class II expression. Understanding this distinction highlights the specific interactions essential for generating effective immune responses.