HLA-A, short for Human Leukocyte Antigen-A, is a crucial component of the Human Major Histocompatibility Complex (MHC) Class I molecules. HLA-A molecules play a central role in the immune system by presenting peptides derived from the endoplasmic reticulum lumen to T-cell receptors, triggering immune responses. HLA-A is critical in determining tissue compatibility between individuals. In organ and bone marrow transplantations, the matching degree of HLA-A is a crucial factor in assessing the risk of transplant rejection. Certain alleles of HLA-A have been associated with the risk of developing specific diseases, such as ankylosing spondylitis and other rheumatic diseases. In transplantation procedures involving bone marrow, kidneys, etc., HLA-A typing is a crucial step to ensure transplant success and minimize rejection risks.