Antigen presentation is a crucial process in the immune system that involves the display of antigens to T cells by antigen presenting cells (APCs), such as dendritic cells, macrophages, and B cells. This process allows the immune system to identify and respond to foreign invaders, such as viruses, bacteria, and cancer cells. Antigen presentation is essential for the activation of T cells and the initiation of an immune response. This research area involves studying the mechanisms and regulation of antigen presentation, as well as its role in various immune responses and diseases.