Shared TCR epitope cross-reactivity could permit dyads of Foxp3+ regulatory and IL-2-producing T cell precursors to escape thymic purge

Abstract

The thymus-derived Foxp3+ regulatory T cells (Tregs) represent a unique population of CD4+ T cells responsible for maintaining dominant tolerance to auto-antigens, beneficial microbiota and potential irritants such as allergens on the one hand and efficient but balanced defense against pathogens on the other. How Tregs with high-affinity TCRs for thymically expressed epitopes survive thymic deletion or display such broad functionality is presently unclear. We recently introduced a novel framework dubbed SPIRAL (SPecific ImmunoRegulatory ALgorithm) which suggests that antigen cross-reactivity of thymic Treg repertoire could provide a mechanistic basis for its broad functionality. Here we further develop this model to propose how escape of high-affinity Tregs from thymic purge could be achieved in dyads with high-affinity natural IL-2-producing T cells (IL-2p T cells) sharing TCR epitope cross-reactivity. We believe this interpretation could reconcile contradictions related to Treg ontogeny in the thymus and their role in modulating antigen-specific immune responses.