Answer:
The Human Leukocyte Antigen (HLA) system, a group of genes in the human major histocompatibility complex, plays a crucial role in how the body recognizes "self" and "nonself" cells. HLA genes code for MHC molecules, specifically HLA class I and class II molecules. HLA molecules present antigens from within the cell (class I) or from outside the cell (class II) to immune cells, aiding in the distinction between self and nonself cells. The unique combinations of HLA molecules on an individual's cells are a key factor in organ transplantation compatibility and immune responses.
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