Background: The presence of a small number of cells of donor origin in organ transplant recipients (microchimerism) may influence allograft survival and may induce tolerance. Postpartum women may be microchimeric to offspring hematopoietic cells up to 27 years. We hypothesized that mothers receiving renal allografts from offspring would have better graft survival compared with either fathers receiving allografts from offspring, or mothers receiving allografts from nonoffspring donors.
Methods: We analyzed 1803 living related kidney transplants from the UNOS database performed between January 1, 1990, and December 31, 1995, for mothers and fathers who received grafts from offspring with one haplotype match. We also compared these mothers with parous females receiving a kidney from nonoffspring donors (spouse and other biologically related or unrelated family members). A multivariate logistic regression method was used to analyze the effect of donor type, as well as other recipient, donor, and transplant characteristics, on graft and patient survival.
Results: Mothers receiving one haplotype-matched offspring renal allografts did not have better graft survival at 1 or 3 years posttransplant compared with fathers receiving similar grafts. There was also no difference in graft or patient survival between mothers receiving kidney grafts from either offspring or nonoffspring donors. Graft survival in mothers with multiple pregnancies was poorer than those with a single pregnancy.
Conclusions: It is possible that persistent microchimerism of fetal cells in maternal circulation may, for some mothers, cause a detectable improvement in graft or patient survival. Comparison of female and male recipients from the UNOS database did not reveal any differences in outcomes. If mothers are tolerant to their offspring, our results indicate that this microchimerism may not improve renal allograft or patient survival in offspring donor to maternal recipient combinations. Lastly, more sensitive pretransplant cross-match assays may need to be implemented in multiparous women, given our results.