IL-21 and TGF-β are required for differentiation of human TH17 cells

Abstract

The recent discovery of CD4 + T cells characterized by secretion of interleukin (IL)-17 (T H 17 cells) and the naturally occurring regulatory FOXP3 + CD4 T cell (nT reg ) has had a major impact on our understanding of immune processes not readily explained by the T H 1/T H 2 paradigm. T H 17 and nT reg cells have been implicated in the pathogenesis of human autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease and psoriasis 1,2 . Our recent data and the work of others demonstrated that transforming growth factor-β (TGF-β) and IL-6 are responsible for the differentiation of naive mouse T cells into T H 17 cells, and it has been proposed that IL-23 may have a critical role in stabilization of the T H 17 phenotype [3][4][5] . A second pathway has been discovered in which a combination of TGF-β and IL-21 is capable of inducing differentiation of mouse T H 17 cells in the absence of ). However, TGF-β and IL-6 are not capable of differentiating human T H 17 cells 2,9 and it has been suggested that TGF-β may in fact suppress the generation of human T H 17 cells 10 . Instead, it has been recently shown that the cytokines IL-1β, IL-6 and IL-23 are capable of driving IL-17 secretion in short-term CD4 + T cell lines isolated from human peripheral blood 11 , although the factors required for differentiation of naive human CD4 to T H 17 cells are still unknown. Here we confirm that whereas IL-1β and IL-6 induce IL-17A secretion from human central memory CD4 + T cells, TGF-β and IL-21 uniquely promote the differentiation of human naive CD4 + T cells into T H 17 cells accompanied by expression of the transcription factor RORC2. These data will allow the investigation of this new population of T H 17 cells in human inflammatory disease.To better understand regulation of IL-17A secretion from human CD4 + T cells, we used a strategy that would allow us to evaluate the effects of various combinations of cytokine on expansion of T H 17 cells from memory T cells versus differentiation of naive CD4 + lymphocytes into T H 17 cells. Specifically, we used high-speed flow cytometry for sorting these two distinct populations of CD4 + T cells from the peripheral blood of healthy subjects: CD4 + CD25 − CD62L + CD45RA hi cells highly enriched for naive T cells and CD4 + CD25 − CD62L + CD45RA − cells enriched for central memory T cells (T CM ; Fig. 1a). All cells enriched for a naive or a central memory phenotype expressed the chemokine receptor CCR7 (data not shown). These two T cell populations were then stimulated with plate-bound

Induction, function and regulation of IL‐17‐producing T cells

“…Furthermore, in a study of patients with genetic traits affecting TGF-b, IL-1, IL-6 and IL-23 production, enhanced TGF-b responses, due to mutations in TGFB1 and TGFBR2, did not alter expression of Th17 cells, whereas mutations in STAT3 and IL-12RB1 impaired dedifferentiation or expansion of Th17 cells in vivo [54]. Three recent reports have demonstrated that TGF-b does have a role in promoting differentiation of human Th17 cells in vitro and that previous failures to identify a role for TGF-b reflected the high content of this cytokine in fetal bovine or human serum used to culture the T cells [53,55,56]. It appears that high concentrations of TGF-b, such as that present in FCS can inhibit Th17 differentiation, but that lower concentrations may promote it.…”

“…Three recent reports have demonstrated that TGF-b does have a role in promoting differentiation of human Th17 cells in vitro and that previous failures to identify a role for TGF-b reflected the high content of this cytokine in fetal bovine or human serum used to culture the T cells [53,55,56]. It appears that high concentrations of TGF-b, such as that present in FCS can inhibit Th17 differentiation, but that lower concentrations may promote it.…”

“…An independent study reported that IL-1b and IL-6 induced differentiation of naïve human T cells into Th17 cells following co-stimulation with anti-CD3 and anti-CD28 in vitro [51]. These studies found that, unlike murine T cells, human naïve T cells did not differentiate into IL-17-secreting T cells in response to TGF-b and IL-6 in vitro [38,50,52,53]. Furthermore, in a study of patients with genetic traits affecting TGF-b, IL-1, IL-6 and IL-23 production, enhanced TGF-b responses, due to mutations in TGFB1 and TGFBR2, did not alter expression of Th17 cells, whereas mutations in STAT3 and IL-12RB1 impaired dedifferentiation or expansion of Th17 cells in vivo [54].…”

“…It appears that high concentrations of TGF-b, such as that present in FCS can inhibit Th17 differentiation, but that lower concentrations may promote it. Yang et al reported that TGF-b and IL-21 can induce differentiation of naïve human T cells cultured in serum-free medium in the presence of anti-CD3 and anti-CD28, whereas IL-1, IL-23 or IL-1 + IL-6 induced IL-17A production by central memory CD4 1 T cells [53]. Manel et al showed that TGF-b with IL-1b, IL-23 and IL-2 promoted development of human Th17 cells in vitro in serum-free conditions; IL-6 or IL-21 also combined with IL-1b and IL-2 to drive Th17 differentiation, but not as effectively as with IL-23 [55].…”

“…Initial studies in humans suggested that TGF-b did not activate IL-17 production, either alone or in the presence of 50,52]. However, recent studies have shown that in association with IL-21 or IL-1 and IL-23, low concentrations of TGF-b do promote human Th17 differentiation [53,55,56]. However, studies in mice showed that while TGF-b acted in synergy with IL-1, IL-23 or IL-6 to promote IL-17 production, it reduced the expression of IL-23R on naïve murine T cells stimulated with .…”