In this study, we analyzed the impact of IL-7/IL-7R signaling com

In this study, we analyzed the impact of IL-7/IL-7R signaling components on the generation, composition and function of circulating Treg. We hypothesized that an impairment of this CHIR-99021 concentration pathway might add to the aberrant T-cell homeostasis and Treg dysfunction associated with MS. Most resting lymphocytes express the IL-7 receptor, which is composed of the IL-7Rα-chain and the common cytokine γ-chain. Basal responsiveness of naïve subsets to IL-7 is important for their sustained survival and facilitates homeostatic cycling and differentiation of RTEs 10, 22. In consistence

with an essential role of IL-7/IL-7R signaling for the maintenance of naïve T cells, we provide evidence that the expression level of the IL-7Rα chain on Tconv is closely linked to the percentage of RTEs defined as CD31-coexpressing naïve T cells within the peripheral T-cell pool. This applies not only to conventional CD4+ T cells as described earlier 11, 12, but also to the Treg subset despite the distinctively lower overall levels of CD127 expressed on Treg, which together with intracellular FOXP3 expression and high surface expression of CD25 defines the Treg phenotype in humans 23–25. The reciprocal relation between IL-7Rα-MFIs on Tconv and plasma concentrations of

IL-7 detectable in our study underlines the tight balance between the components of this signaling pathway. Here, we show that the amount of IL-7Rα expressed on the surface of Tconv and Selleckchem Mitomycin C Tconv subsets is significantly decreased in patients with MS. As an important finding, reduced IL-7Rα-MFIs in MS-derived Tconv strongly correlated with both reduced frequencies of RTE-Tconv and RTE-Treg and with reduced Treg-mediated inhibitory activities. Therefore, by determining the prevalences of circulating RTE-Treg, IL-7Rα expression appears to affect the suppressive capacity of total Treg, which is in line with previous studies demonstrating that proportions of RTE-Treg are critical for the function of total Treg 2, 3. A decline of IL-7Rα-MFIs was detectable

in approximately two-thirds of patients with MS, whereas 30% of patients showed HC-like levels of IL-7Rα together with normal RTE-frequencies and normal Treg functions. This observation is consistent with earlier findings of a minority of MS patients 5-Fluoracil mouse exhibiting normal Treg homeostasis and suppressive properties 26. Of note, IL-7Rα expression on Tconv and RTE-Treg were decreased in HC donors of older age whereas age related effects were abolished in MS patients. This substantiates the assumption that immunosenescence might play a role in the development of this disorder 27. As a typical phenotypic feature of the Treg subset IL-7Rα expression is downregulated on circulating Treg 23–25. As expected, we found low levels of IL-7Rα on Treg and Treg subsets in all blood samples analyzed (data not shown). Thus, the MS-related reduction of IL-7Rα-MFIs on Tconv was not detectable in Treg.

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