Other findings show that TSLP plays an important role in the expansion and survival of CD4 + T cells (47). patients. CD31, a marker lost with excessive immunoreactivity, was significantly reduced in thymic but not blood resting Treg. These results suggest that an altered thymic environment may explain Treg differences between MG patients and controls. Since thymic epithelial cells (TECs) play a major role in the generation of Treg, we co-cultured healthy thymic CD4 + T cells with control or MG TECs and tested their suppressive function. Co-culture with MG TECs consistently hampers regulatory activity, as compared with control TECs, suggesting that MG TECs contribute to the immune regulation defects of MG CD4 + T cells. MG TECs produced significantly higher thymic stromal lymphopoietin (TSLP) than control TECs, and a neutralizing anti-TSLP antibody partially restored the suppressive capacity of Treg derived from co-cultures with MG TECs, suggesting that TSLP contributed to the defect of thymic Treg in MG patients. Finally, a co-culture of MG CD4 + T cells with control TECs restored figures and function of MG Treg, demonstrating that a favorable environment could correct the immune regulation defects of T cells in MG. Altogether, our data suggest that the severe defect of thymic Treg is at least partially due to MG TECs that overproduce TSLP. The Treg defects could be corrected by replacing dysfunctional TECs by healthy TECs. These findings highlight the role of the tissue environment around the immune regulation. 0.05. Each physique story mentions the statistical test used. Other statistical tests have been used and are indicated in the text (One-way anova to compare 3 groups and Spearman non-parametric correlation). Results Functional Characterization of Thymic MDM2 Inhibitor and Peripheral Regulatory Cells The suppression function of Treg is usually profoundly impaired in the MG thymus (10). In order to investigate whether peripheral Treg behave similarly, we compared the suppressive function of Treg isolated from your thymus or from peripheral blood cells from MG and control donors. In both compartments, the suppressive function was impaired in MG patients. In the thymus, the average proliferation was 23.0% for controls and 81.1% for MG patients (Determine 1A, 0.001). In PBMCs, the average proliferation was 29.4% for controls and MDM2 Inhibitor 60.8% for MG patients (Determine 1B, 0.04). While in the thymus, there was no overlap between MG and control values, it was not the case for PBMC results (Figures 1A,B). Open in a separate window Physique 1 The suppression function is usually more impaired in the thymus than in the periphery in MG patients. Percentages of proliferation of Tconv in co-culture with MDM2 Inhibitor Treg (ratio 1:1) from control IL12RB2 individuals (CTRL) or patients with myasthenia gravis (MG) using cells derived from the thymus (A) or from PBMCs (B). Data symbolize the imply standard error of the imply. Statistical test: Two-tailed 0.05; ?? 0.01; and MDM2 Inhibitor ??? 0.005, gray star corresponds to 0.1). (F) Statistical summary of the data shown in (BCE). Colorized bubbles correspond to significant differences. Size is usually proportional to the statistical significance and color represents fold switch between mean values of control individuals and MG patients (green, lower value in MG; reddish, higher value in MG). To characterize more precisely the phenotypic changes of the subsets defined with CD45RA (rTReg, eTreg FIII) in the thymus and PBMCs, we decided imply fluorescent intensities of markers associated with Treg function. In the thymus of MG patients, CD25 expression was significantly reduced in eTreg but not in the other subsets while in PBMCs a decrease in CD25 expression was observed in FIII (Physique 2B) but not in the other subsets. The level of CD127.