Unexplained post-renal transplant tolerance: a case report.

Achievement of an immunosuppression-free condition defined as clinical operational tolerance is an ideal goal. We hereby report a case of clinical operational tolerance in a patient whose allograft is functioning normally, without immunosuppression, for more than 3 years. The patient withdrew from immunosuppression in 2011 following which his serum creatinine was 1.34 mg/dl and proteinuria was 178 mg/24 h. Flowcytometric studies showed an elevated number of B lymphocytes and NK cells. IL-10 cytokine levels had increased, whereas those of IFN-γ decreased, suggesting that both B lymphocytes and NK cells, with their immunoregulatory function, contribute to the maintenance of long-term graft function. Consequently, further studies in understanding the interactions of NK cells and B lymphocytes may give us a better insight into the underlying mechanisms that underpin organ tolerance.