A clinical research consortium sponsored by NIAID and JDRF
Newell KA, Asare A, Kirk AD, Suthanthiran M, Burlingham WJ, Bourcier K, Marks WH, Turka LA, Seyfert-Margolis V, Gisler T
Department of Surgery, Emory University, Atlanta, GA; Immune Tolerance Network, UCSF, San Francisco, CA; Department of Medicine, Cornell University, New York, NY; Department of Surgery, University of Wisconsin, Madison, WI; Organ Transplant Program, Swedish Medical Center, Seattle, WA; Department of Medicine, University of Pennsylvania, Philadelphia, PA
Introduction. Biomarkers predictive of tolerance are key tools for protocols studying immunosuppression minimization/discontinuation. We report on the identification tolerance markers in renal transplant recipients.
Methods. An initial cohort of tolerant kidney transplant recipients (TOL, off all IS for > 1yr with stable function, N=19) were compared to recipients with stable function on standard immunosuppression (SI, N=24), and healthy controls (HC, N=18). A separate cohort of TOL (n=6) SI (n=6) HC (n=24) were recruited as an independent test set for biomarker testing. Initial biomarkers were defined using microarrays on peripheral blood RNA, flow cytometry on whole blood and PCR of urine lymphocytes. Independent verification of these markers was performed using multi-plex real time PCR on all subjects (initial and test set), and flow cytometry on the second test set of participants. Finally, extensive B cell subset analysis was performed on frozen PBMC's from all participants.
Results. We initially defined that tolerant participants exhibited a novel signature of increased B cells in the peripheral blood, as well as increases in B cell development genes. Multi-plex real time PCR analyses of initial and test set samples from the TOL and SI identified 3 transcripts, all corresponding to immunoglobulin variable region genes, that distinguish TOL from SI patients, with 100% accuracy for TOL and 83% accuracy for SI on the test set samples. Independent verification of the initial flow cytometry B cell signature was obtained using samples from the test set described above. B cell subtyping identified increased navie Bcell numbers in the TOL vs. the SI and HC groups.
Conclusions. These data suggest that an increases in B cell numbers and in the genes they express may identify tolerant renal transplant recipients. The powerful predictive value of a very small number of genes makes this approach clinically feasible and may facilitate rational design of tolerance-inducing regimens.
