Abstract: The inventors have made the surprising discovery that SGK1, a serine/threonine kinase previously described as being involved in regulation of cellular sodium homeostasis, has a novel and unexpected function in the differentiation and function of a specific subset of CD4 T cells, the TH17 lineage. Described herein are methods and compositions for modulation of TH17 cell differentiation, proliferation, and/or function that rely upon modulating the activity or expression of SGK1. Such methods and compositions are useful in the treatment of disorders including autoimmune diseases, chronic inflammatory conditions, infectious diseases, and cancer.