TCR-dependent generation of natural Foxp3+ CD4+ regulatory T cells (Treg) in the thymus is essential for maintaining self-tolerance. Although a simply affinity model of self-antigen recognition is widely accepted as governing thymic Treg development, it is poorly substantiated experimentally. To address the mechanism by which TCR interactions with peptide:MHC complex result in Treg development, we are analyzing the ability of a variety of TCRs to facilitate Treg development due to interactions with OVA(323-339) expressed via the RIP-mOVA transgene. To obtain TCRs with varying reactivity to OVA, we sequenced TCR-alpha chains of proliferating CD4+ T cells from DO11 TCR-beta transgenic mice stimulated in vitro with OVA peptide. OVA reactivity was confirmed by retroviral transduction of individual TCRs into a hybridoma cell line expressing an NFAT-GFP reporter for TCR activation. Approximately 9 TCRs have thus far been obtained that show up to 1000-fold differences in sensitivity to OVA in vitro. Sensitivity to OVA appeared to correlate with the ability to facilitate RIP-mOVA dependent Treg development. Using DO11-alpha-beta TCR as a reference point for TCR-cognate peptide interaction, one TCR with a 1,000 fold lower reactivity to OVA was unable to facilitate Treg development, whereas TCRs within 100-fold sensitivity were capable. Thus, these preliminary data allow us to begin to quantify the nature of TCR interactions with peptide:MHC required for Treg selection.
- Copyright © 2011 by The American Association of Immunologists, Inc.