Any of various antigens on the surface of cell membranes that serve to identify a cell as self or nonself. These antigens determine whether a tissue graft or transfusion will be accepted by a recipient.组织相容性抗原：机体各种组织的有核细胞表面具有能诱发移杆体相排斥的相同抗原，这种抗原决定组织移植或输血能否被接受