Zusammenfassung
The vast majority of Foxp3(+) regulatory T cells (Tregs) are generated in the thymus, and several factors, such as cytokines and unique thymic antigen-presenting cells, are known to contribute to the development of these thymus-derived Tregs (tTregs). Here, we report the existence of a specific subset of Foxp3(+) Tregs within the thymus that is characterized by the expression of IL-1R2, which is ...
Zusammenfassung
The vast majority of Foxp3(+) regulatory T cells (Tregs) are generated in the thymus, and several factors, such as cytokines and unique thymic antigen-presenting cells, are known to contribute to the development of these thymus-derived Tregs (tTregs). Here, we report the existence of a specific subset of Foxp3(+) Tregs within the thymus that is characterized by the expression of IL-1R2, which is a decoy receptor for the inflammatory cytokine IL-1. Detailed flow cytometric analysis of the thymocytes from Foxp3(hCD2)xRAG1(GFP) reporter mice revealed that the IL-1R2(+) Tregs are mainly RAG1(GFP-) and CCR6(+)CCR7(-), demonstrating that these Tregs are recirculating cells entering the thymus from the periphery and that they have an activated phenotype. In the spleen, the majority of IL-1R2(+) Tregs express neuropilin-1 (Nrp-1) and Helios, suggesting a thymic origin for these Tregs. Interestingly, among all tissues studied, the highest frequency of IL-1R2(+) Tregs was observed in the thymus, indicating preferential recruitment of this Treg subset by the thymus. Using fetal thymic organ cultures (FTOCs), we demonstrated that increased concentrations of exogenous IL-1 beta blocked intrathymic Treg development, resulting in a decreased frequency of CD25(+)Foxp3(+) tTregs and an accumulation of CD25(+)Foxp3(-) Treg precursors. Interestingly, the addition of IL-1R2(+) Tregs, but not IL-1R2(-) Tregs, to reaggregated thymic organ cultures (RTOCs) abrogated the IL-1 beta-mediated blockade, demonstrating that these recirculating IL-1R2(+) Tregs can quench IL-1 signaling in the thymus and thereby maintain thymic Treg development even under inflammatory conditions.
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