Microchimerism and Renal Transplantation: Doubt Still Persists

Background: The Presence of donor leukocytes in recipients of organ allograft has been shown even several years after transplantation. However, it remains unclear whether this donor cell microchimerism plays an effective role in allograft acceptance or is simply a consequence of immunosuppressive conditions in recipients. Objective: To study microchimerism in a group of kidney transplant recipients. Methods: In this study, the Peripheral Blood Microchimerism (PBM) after renal transplantation was retrospectively evaluated in 32 male-to-female recipients of living (unrelated) and cadaveric donor renal transplants. Using a Nested Polymerase Chain Reaction (Nested-PCR) amplification specific for SRY region of the Y chromosome, microchimerism was detected with a sensitivity of 1:1000000. Recipients were classified and compared according to the presence of PBM, acute and chronic rejection episodes, type of allotransplant, recipient and donor age at transplantation, previous male labor or blood transfusion, allograft function (serum creatinine level), and body mass index. Results: Among 32 recipients, 7 (21.9) were positive for PBM in multiple testing at different post-transplantation times. All microchimeric recipients had received kidney from living-unrelated donors. No significant difference was observed with regard to other parameters mentioned above. In addition, acute rejection rate in the microchimeric group was 3 (42%) versus 4 (16%) in the nonmicrochimeric recipients (not significant). Conclusion: Our results demonstrate better establishment of microchimerism after living donor kidney transplantation. However, concerning the true effect of microchimerism after renal transplantation doubt still persists; and it seems that microchimerism alone has no major protective role in renal allograft survival.