Distinct metabolic programs support the differentiation of CD4+T cells into their separate lineages. In this study, we investigated metabolic mechanisms underlying the differentiation of IL-9 producing-CD4+T cells (TH9) in allergic airway inflammation and cancerous tumors. We found here that SIRT1 negatively regulates TH9 differentiation. A deficiency of SIRT1 induced by either conditional deletion in mouse CD4+T cells or the use of small interfering RNA (siRNA) in mouse or human T cells increased IL-9 production, whereas ectopic SIRT1 expression inhibited it. Notably, SIRT1-inhibited the differentiation of TH9 cells that regulated anti-tumor immunity and allergic pulmonary inflammation. Glycolytic activation through the mTOR-hypoxia-inducible factor-1α (HIF1α) pathway was required for the differentiation of the TH9 cells that confer protection against tumors and are involved in allergic airway inflammation. Our results define the essential features of a SIRT1-mTOR-HIF1α signaling-coupled glycolytic pathway in inducing TH9 cell differentiation, with implications for metabolic reprogramming as an immunotherapeutic approach. Lymphocytes were isolated from the spleen and lymph nodes of mice and sorted on a FACSAria II (Becton Dickinson). The sorted naïve T cells (CD4+TCR+CD62Lhi CD44lo) from WT or SIRT1flox/flox-CD4-Cre mice were used for in vitro culture. T cells were activated with 2 ug/ml anti-CD3 (2C11; Bio X Cell), 2 ug/ml anti-CD28 (37.51; Bio X Cell) and 100 U/ml human IL-2. For TH9 cell differentiation, cultures were supplemented with 10 ng/ml IL-4 (R&D system), 2 ng/ml TGFβ1 (R&D system). After 5-6 d culture, differentiated T cells were collected and for microarray assay.