Synergistic Role of DGKalpha and zeta in Regulatory T cell function, stability, and pathogenecity
Regulatory T cells (Tregs) actively engage in immune suppression to prevent autoimmune diseases but also inhibit anti-tumor immunity. Although Tregs express a TCR repertoire with relatively high affinities to self, they are normally quite stable and their inflammatory programs are intrinsically suppressed. We report here that diacylglycerol kinases (DGK) alpha and zeta are crucial for homeostasis, suppression of proinflammatory programs, and stability of Tregs and for enforcing their dependence on CD28 costimulatory signal. Treg-specific deficiency of both DGKa and z derails signaling, metabolic, and transcriptional programs in Tregs to cause dysregulated phenotypic and functional properties and to unleash conversion to pathogenic exTregs, especially exTreg-T follicular helper (Tfh) 2 cells, leading to uncontrolled effector T cell differentiation, deregulated germinal center B cell responses and IgG1/IgE predominant antibodies/autoantibodies, and multiorgan autoimmune diseases. Our data not only illustrate the crucial roles of DGKs in Tregs to maintain self-tolerance but also unveil a Treg-to-self-reactive-pathogenic-exTreg-Tfh-cell program that is suppressed by DGKs and that could exert broad pathogenic roles in autoimmune diseases if unchecked. Overall design: Splenocytes and lymph node cells from WT-Foxp3YFPiCre and DGKa-/-zf/f-Foxp3YFPiCre mice were enriched for CD4+ T cells using magnetic beads.  Enrichment of CD4+ T cells were sorted into CD4+CD8-Foxp3YFP+ regulatory T cells (Tregs) and CD4+CD8-Foxp3YFP- conventional T cells (Tcons). Total RNA from sorted Tregs and Tcons were purified and subjected to mRNAsequencing.