114-P: REGULATORY T AND B CELL CIRUITS IN TOLERANT HLA-IDENTICAL KIDNEY TRANSPLANT RECIPIENTS AND NORMAL VOLUNTEERS

Abstract

In an HLA Identical (HLA-id) renal transplant (RT) tolerance trial using donor hematopoietic stem cells, alemtuzumab induction, and temporary maintenance immunosuppression (IS), primarily with sirolimus, 6 of the first 12 recipients achieved non-chimeric tolerance (IS-free for over 1 year without rejection in biopsies at >3 years post-op). We assessed the phenotypic and functional T and B regs present in these tolerant vs. non-tolerant recipients compared with T and B regs generated in vitro in MLRs of normal volunteers. We tested the generation of Bregs (CD19 + IL10 + ) and Tregs (CD4 + CD25 high CD127 − FOXP3 + ) interactively in MLR both in HLA-id tolerant recipients and normal volunteers. All recipients developed significantly higher percentages of phenotypic Treg and naïve B cells (containing putative Bregs) post-RT. In tolerant vs. non-tolerant recipients, unselected post-RT PBMC (>18 months) (vs. pre-RT PBMC) added into recipient donor specific MLRs, augmented of newly generated Bregs and Tregs (P < 0.02; n=5 thus far tested). In normal laboratory volunteers, i mmunoselected CD127 − CD4 + CD25 + Tregs generated in 7-day MLRs, added as third component modulators, inhibited proliferation of fresh MLR readouts from the same pairs and augmented the generation of new responder Bregs by 5-10 fold. This was in contrast to PBMC modulator controls (n=12). The Bregs in turn could secondarily generate additional Bregs and Tregs. [figure1] These results suggest that long-lasting functional Treg and Breg circuits are generated in tolerant non-chimeric HLA-id recipients. Such assays might be used to discriminate between tolerant and non-tolerant recipients.