Distinct peripheral blood molecular signature emerges with successful tacrolimus withdraw in kidney transplant recipients

Tacrolimus (Tac) is an effective anti-rejection agent in kidney transplantation, but its off-target effects make withdrawal desirable. While studies indicate that Tac can be safely withdrawn in a subset of kidney transplant recipients, immune mechanisms that underlie successful vs. unsuccessful Tac removal are unknown. We performed microarray analyses of PBMC RNA from subjects enrolled in the Clinical Trials in Organ Transplantation-09 study in which stable kidney transplant recipients were randomized to Tac withdrawal or maintenance of standard immunosuppression beginning 6-mo post-transplant. Eight of 14 subjects attempted but failed withdrawal, while six developed stable graft function for ≥2 years on mycophenolate mofetil plus prednisone. Whereas failed withdrawal upregulated immune activation genes, successful Tac withdrawal was associated with a distinct, T cell-specific, downregulatory, and pro-apoptotic gene program. Functional analyses suggested stronger donor-reactive immunity in subjects who failed withdrawal without evidence of regulatory T cell dysfunction. Together, our data suggest that successful Tac withdrawal can unleash an active, protective pro-apoptotic T cell program, and provide the foundation for developing strategies to promote this protective immunological phenotype in kidney transplant recipients. Samples of PBMCs obtained from patients 6 months post kidney transplant randomized to no withdrawal (N=4) and Tac withdrawal (N=14), and 3 months post Tac withdrawal when tapering was completed. See PMID: 25925687 for more references.