Increased Apoptosis and aberrant apoptosis signaling pathways of CD4+CD25+FOXP3+ regulatory T cells in patients with systemic lupus erythematosus

Background: Systemic Lupus Erythematosus (SLE) is a prototype of autoimmune disease. Decreased cell numbers and suppressive defects of naturally occurring CD4+CD25+FOXP3+ regulatory T cells (Tregs) play an important role in the breakdown of SLE immune tolenrance. We have peviously observed significantly increased apoptosis of peripheral blood CD4+ T cells in SLE patients. Our objective here was to detect the apoptosis of Tregs in SLE patients to see if it could contribute to reduced suppressive activity of Tregs, and further elucidate the genes and signaling pathways which trigger the apoptosis in these cells. Methods and findings: The cell number and apoptosis rates of Tregs was respectively evaluated in SLE patients and normal controls (NCs) by FACS. The suppressive activity of Tregs was measured by coculture with CD4+CD25-CD127dim/- T cells. The relationship of abnormal Tregs apoptosis with clinical parameters was analyzed by Pearson correlation analysis. Gene expression profiles of unstimulated Tregs from active SLE patients and NCs were generated by microarray analysis. Differential genes expression was verified by real time-PCR. We found that the Tregs from SLE patients showed a significantly reduced number, elevated apoptosis rates and impared suppressive capacity compared to NCs. The increased apoptosis of Tregs was negatively correlated with the total number of Tregs and positively correlated with disease activities. Gene expression profiles of unstimulated Tregs from recent-onset SLE subjects reveal a cellular response that could make the cells sensitive to apoptosis, partially due to the stress responses, DNA-damaging and cytokine stimulation. This global picture of pathway-specific expression signatures is a step further into dissecting Tregs defects in the pathogenesis of SLE. 3 recent-onset and untreated female SLE patients whose disease activity were all considered severe and 3 age-, gender-, and ethnically matched healthy female subjects were selected to perform microarray analysis. 20ml peripheral blood was freshly extracted, CD4+CD25+CD127dim Tregs cells were isolated by immunomagnetic beads. Mixed Tregs of 3 normal controls as one normal sample for gene expression profile detection. As for the normal control samples, we extracted the peripheral blood of three healthy subjects, separated the peripheral blood Tregs of them respectively, and then mixed the three Tregs together as one normal control sample for microarray detection.