Tissue typing is a medical test used to determine the compatibility of tissues between a donor and a recipient, especially in organ transplants. It involves analyzing specific proteins, known as human leukocyte antigens (HLAs), on the surface of cells. Matching these proteins helps reduce the risk of transplant rejection, where the recipient's immune system attacks the new tissue. The process typically includes a blood sample from both the donor and recipient. Laboratory techniques identify the HLA types, allowing doctors to assess how well the tissues match. Accurate tissue typing is crucial for successful transplants and improving patient outcomes.