IL-17 cytokines preferentially act on naïve CD4+ T cells

CD4+ Th17 T cells are a key helper population in the regulation of both protective immunity during infection and in self-tolerance. Through the secretion of IL-17, Th17 cells act in promotion of inflammation and thus a major therapeutic target for autoimmune disorders. Recent reports have brought to light that the IL-17 family cytokines, IL-17A, IL-17F and IL-17AF, can directly act on CD4+ T-cells, both in murine and human systems. Here we show that this action is preferentially targeted toward naïve, but not memory, CD4+ T-cells. Moreover, IL-17A, IL-17F and IL-17AF led to reduction in immune signaling genes, but an increase in interferon responsive genes across all treatments. In addition, IL-17A, IL-17F and IL-17AF treatment possessed differences in downstream transcriptional signaling, with IL-17AF heterodimer conferring both the greatest transcriptional change and suppressed phenotype. Detailed transcriptome analysis provides important functional insights into the genes and pathways that are modulated as a result of IL-17-mediated signaling. Overall design: mRNA profiles of ex vivo-purified bulk CD4+CD25- CD45RO+ memory T-cells were activated in vitro for 48 or 168 hours in the presence of media alone (controls), or 10 ng/ml of IL-17A, IL-17F or IL-17AF