Which factor is crucial when selecting a kidney donor for transplantation?

• A. Blood type compatibility and HLA matching with donor.
• B. Height difference.
• C. Skin color.
• D. Hair color.

Answer: (A)

Immunologic compatibility between donor and recipient is the essential factor in selecting a kidney donor. The most important pieces are ABO blood type compatibility and matching of HLA antigens. ABO compatibility prevents immediate, antibody-driven rejection because the recipient has antibodies against nonself A or B antigens; an incompatible blood type can trigger hyperacute or rapid rejection of the graft. HLA matching involves several antigens on donor cells that the immune system recognizes as foreign; closer matches reduce the likelihood of T-cell– and antibody-mediated rejection, improving long-term graft survival. Before a transplant, a crossmatch is performed to see if the recipient has antibodies against the donor’s HLA; a positive crossmatch raises the risk of severe rejection and typically contraindicates the transplant. If the crossmatch is negative and ABO compatibility is present, the transplant is more likely to succeed with the planned immunosuppressive regimen. In contrast, factors like height, skin color, or hair color do not influence immune compatibility or graft outcomes and are not relevant to donor suitability.