Abstract
Background During pregnancy contact with paternal HLA-antigen can lead to activation of maternal immune system while exposure of the child to the non inherited (NIMA) antigens may lead to tolerance due to immaturity of the child immune system in utero. Multiple studies on hematopoietic stem cell transplantation demonstrate this beneficial effect but studies on NIMA-specific tolerance in renal transplant are generally few and demonstrated improved kidney graft from sibling who is mismatched at the NIMA haplotype. We report here a case of a successful kidney retansplant from a sibling who is mismatched at the NIMA after failed initial graft from the mother. 26-year-old female with ESRD was referred for second kidney transplantation. Her mother offered the first graft which shortly after the transplantation possibly due to chronic rejection. Investigation revealed weak DSA against DQ2. A haploidentical brother offered the second NIMA-mismatched graft. FXM results were negative for both T and B with second donor. She received Thymoglobulin induced second transplant from her brother. The first post transplant SAB results showed remarkable increase in DQ2, MFI of 11380. We alerted the clinician to this increment in DSA, so he put the patient under close observation despite normal creatinine level. A kidney biopsy was unremarkable. Because of persistence elevation of DSA in view of normal kidney function the treating team questioned our reports and a second biopsy was performed which showed the same findings, however C4d was focally positive in the second biopsy. Consequently the patient received full rejection therapy. The lack of expected response in DSA level guided us to reanalyze our data. HR typing confirmed HLA-DQB1∗02:02 associated with DQA1∗02:01 for both donors but careful analysis of DQ2 coated bead reaction showed that what we reported as DSA was actually non donor specific and directed against sub group of DQ2 indicating tolerance to mismatch NIMA despite repeated exposures. Our case is a further confirmation for the superior graft outcome from sibling expressing NIMA compared to maternal graft expressing the same NIMA.
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