The TNF family member TL1A induces IL-22 secretion in committed human TH17 cells via IL-9 induction

TL1A contributes to the pathogenesis of several chronic inflammatory diseases, including Inflammatory Bowel Diseases by enhancing TH1, TH17, and TH2 responses. TL1A mediates a strong co-stimulation of these TH subsets particularly of mucosal CCR9+ T cells. However, the signaling pathways that TL1A induces in different TH subsets are incompletely understood. Here, we investigated the function of TL1A on human TH17 cells. TL1A together with TGF- IL-6, and IL-23 enhanced the secretion of IL-17 and IFN- from human CD4+ memory T cells. TL1A induced the expression of the transcription factors BATF and T-bet that correlated with the secretion of IL-17 and IFN-. In contrast, TL1A alone induced high levels of IL-22 in memory CD4+ T cells and committed TH17 cells. However, TL1A did not enhance expression of IL-17A in TH17 cells. Expression of the transcription factor aryl hydrocarbon receptor that regulates expression of IL-22 was not affected by TL1A. We performed transcriptome analysis of TH17 cells to determine genes that are transcriptionally regulated by TL1A. transcriptome analysis revealed increased expression of IL-9 in response to TL1A. Total RNA was obtained from human TH17 cells (sorted by flow cytometry for CD4+ CD45RO+ CCR6+) that were untreated (control) or treated with TL1A (TL1A) for 24, 48, or 72 h. Total RNA was extracted from 5 healthy donors (5 independent experiments).