Regulatory, effector, and cytotoxic T cell profiles in long-term kidney transplant patients

Animal studies have suggested a potential role for regulatory T cells (Tregs) in allograft tolerance, but these FOXP3+ cells seem to be an inherent component of acute rejection (AR) in human recipients of renal transplants. The balance between regulatory cells and effector/cytotoxic cells may determine graft outcome; this balance has not been described for chronic allograft injury. We investigated the expression of key regulatory, effector, and cytotoxic transcripts (i.e., FOXP3, T-bet, and granzyme B, respectively) in the grafts and peripheral blood of long-term-surviving renal transplant patients. We found that, whereas neither intragraft nor peripheral blood FOXP3 or T-bet mRNA could distinguish between rejection and nonrejection status, granzyme B (GrzB) mRNA could: It was significantly increased in the graft and significantly decreased in the peripheral blood of patients with chronic antibody-mediated rejection (CAMR). Quantifying peripheral blood GrzB mRNA demonstrated potential to aid in the noninvasive diagnosis of CAMR. In summary, these data affirm GrzB as a marker not only for AR but also for CAMR. In addition, we identified several previously unreported clinical or demographic factors influencing regulatory/effector/cytotoxic profiles in the peripheral blood, highlighting the necessity to consider confounding variables when considering the use of potential biomarkers, such as FOXP3, for diagnosis or prognosis in kidney transplantation.