Kidney Transplant Compatibility: Why Relatives Aren't Always Matches

Matching Criteria

• ABO blood group: Must be compatible (O universal donor; AB universal recipient).
• HLA typing: Match at HLA‑A, ‑B, ‑DR loci; fewer mismatches → lower rejection risk.
• Crossmatch: Recipient serum vs. donor lymphocytes; positive = high rejection risk (contraindication).
• Non‑HLA antibodies: MICA, AT1R, etc., also matter.

When Relatives Are Incompatible

• ABO mismatch (e.g., donor A, recipient B).
• High HLA mismatches despite relatedness.
• Pre‑formed donor‑specific antibodies (DSA) in recipient.

Alternatives

• Paired kidney exchange (KPD).
• Deceased donor waitlist.
• Desensitization protocols (for low‑level DSA).