Invariant Natural Killer T (iNKT) cells have been implicated in lung inflammation in humans and also shown to be a key cell type in inducing allergic lung inflammation in mouse models. iNKT cells differentiate and acquire functional characteristics during development in the thymus. However, the correlation between development of iNKT cells in the thymus and role in lung inflammation remains unknown. In addition, transcriptional control of differentiation of iNKT cells into iNKT cell effector subsets in the thymus during development is also unclear. In this report we show that β-catenin dependent mechanisms direct differentiation of iNKT2 and iNKT17 subsets but not iNKT1 cells. To study the role for β-catenin in lung inflammation we utilize mice with conditional deletion and enforced expression of β-catenin in a well-established mouse model for IL-25-dependen lung inflammation. Specifically, we demonstrate that conditional deletion of β-catenin permitted development of mature iNKT1 cells while impeding maturation of iNKT2 and 17 cells. A role for β-catenin expression in promoting iNKT2 and iNKT17 subsets was confirmed when we noted that enforced transgenic expression of β-catenin in iNKT cell precursors enhanced the frequency and number of iNKT2 and iNKT17 cells at the cost of iNKT1 cells. This effect of expression of β-catenin in iNKT cell precursors was cell autonomous. Furthermore, iNKT2 cells acquired greater capability to produce type-2 cytokines when β-catenin expression was enhanced. This report shows that β-catenin deficiency resulted in a profound decrease in iNKT2 and iNKT17 subsets of iNKT cells whereas iNKT1 cells developed normally. By contrast, enforced expression of β-catenin promoted the development of iNKT2 and iNKT17 cells. It was important to note that the majority of iNKT cells in the thymus of C57BL/6 mice were iNKT1 cells and enforced expression of β-catenin altered the pattern to iNKT2 and iNKT17 cells suggesting that β-catenin may be a major factor in the distinct pathways that critically direct differentiation of iNKT effector subsets. Thus, we demonstrate that β-catenin expression in iNKT cell precursors promotes differentiation toward iNKT2 and iNKT17 effector subsets and supports enhanced capacity to produce type 2 and 17 cytokines which in turn augment lung inflammation in mice.
Abstract During late stages of T cell development, positively selected CD4+CD8+ (DP) thymocytes must make a lineage choice decision to become MHC-I-restricted cytotoxic CD8+ T cells or MHC-II-restricted helper CD4+ T cells. This lineage choice process is determined by extrinsic signals such as TCR and γc cytokines and by intrinsic transcriptional factors such as Myb, Gata3, ThPOK and Runx. The canonical Wnt effector transcription factors, TCF-1 and LEF-1, are essential for the transition from CD4-CD8- (DN) to the DP stage, but their requirement beyond the DP stage is unknown. Here we show that deficiency in TCF-1 resulted in a preferential loss of CD4+ T cells and reduced CD4/CD8 ratio, and this phenotype was exacerbated upon loss of both TCF-1 and LEF-1. By crossing TCF-1-/- mice to MHC-I-deficient strain or OT-2 CD4+ TCR transgenic strain, we found that DP thymocytes selected on MHC-II were re-directed to the CD8 lineage in the absence of TCF-1 and/or LEF-1. Mechanistically, we observed that Myb expression is greatly diminished in post-select DP thymocytes lacking TCF-1 and/or LEF-1, and that activation of the Wnt signaling pathway in post-select DP thymocytes induced Myb expression. Collectively, these findings revealed a novel role of Wnt effectors TCF-1 and LEF-1 in promoting CD4+ lineage choice, which is likely mediated by Wnt-dependent upregulation of Myb.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)