MHCII, or major histocompatibility complex class II, is a group of cell surface proteins that play a key role in the immune system by presenting antigens to T-cells. This process is crucial for the activation of T-cells and the initiation of an immune response against pathogens. MHCII proteins are primarily expressed on antigen presenting cells such as dendritic cells, macrophages, and B cells. Research in the MHCII field focuses on understanding the structure and function of these proteins, as well as their role in various diseases such as autoimmune disorders, infectious diseases, and cancer. Additionally, researchers are investigating how MHCII proteins can be targeted for therapeutic interventions, such as in vaccine development or immunotherapy.