Human Leukocyte Antigen (HLA) Class II molecules are proteins found on the surface of certain immune cells, including dendritic cells, macrophages, and B cells. They play a critical role in the immune system by presenting processed antigens to CD4+ T helper cells, initiating immune responses. This antigen presentation is crucial for the activation and regulation of the immune system, particularly in recognizing and responding to foreign pathogens, as well as abnormal cells, such as those found in cancer.
