A5

A5 refers to a classification of a specific type of human leukocyte antigen (HLA), which is part of the immune system. These antigens help the body recognize and distinguish between its own cells and foreign invaders like bacteria or viruses. The "A5" designation identifies a particular genetic variation within the HLA-A gene, important in contexts like organ transplantation, where matching these antigens between donor and recipient reduces the risk of rejection. In essence, A5 is a specific genetic marker that plays a crucial role in immune response and compatibility assessments.