PIK3CD and Autoimmunity: Compared to their function in the development of autoimmunity, the roles of PI3K-Akt-mTORC1 signaling and HIF-1 of CD4+ T cells in the host defense are still largely unknown, despite the major roles of PI3K-Akt-mTORC1 pathway in APCs to regulate Th1- and Th17-type immune reactions (Fukao et al. 2002; Ohtani et al. 2008; Weichhart et al. 2008).