These results are in agreement with a recent study showing that STAT5-mediated signaling induced GM-CSF expression in human naïve and memory CD4+ T cells, whereas STAT3 signaling blocked it [6]. In fact, dysregulation of the IL-7/IL-7R axis has long been implicated in autoimmune diseases, such as type 1 diabetes, multiple sclerosis and rheumatoid arthritis [7, 8]. Thus, the results from Sheng et al. may now provide a mechanistic link between IL-7/STAT5-mediated signaling and T helper cell-mediated pathogenicity.