histocompatibility antigen

Histocompatibility antigens, also known as human leukocyte antigens (HLAs) in humans, are substances on cell surfaces that help the immune system distinguish between the body's own cells ("self") and foreign invaders ("non-self"). These antigens are encoded by a group of genes called the major histocompatibility complex (MHC), located on chromosome 6.12

The MHC genes produce proteins that display fragments of other molecules on the cell surface. Immune cells, like T lymphocytes, recognize these fragments. If the fragment is foreign (e.g., from a virus or bacterium), the immune system mounts a response. This system is crucial for fighting infections and also plays a role in tissue transplantation, as differences in histocompatibility antigens can lead to rejection. Certain HLA genes are also linked to autoimmune disorders and cancer.231