human leukocyte antigen (HLA)

A protein found on the surface of all cells, including white blood cells (leukocytes) and platelets, that plays a role in the immune system’s response to foreign substances.

HLAs are typed in a similar way to red blood cells (A, B, O or AB). HLA typing is done before stem cell or organ transplant to make sure that the donor’s tissues match the recipient’s.

Also called human leukocyte-associated antigen or human lymphocyte antigen.