Invariant NKT cells are unusually refractory to glucocorticoid-induced apoptosis but exhibit impaired functional fitness and fail to trigger antitumor immunity following physiological stress

Abstract

Abstract The nervous system serves critical roles in the regulation of immune responses. Consequently, the neuroimmune functional interface can be disrupted by physiological stress, potentially impeding our ability to combat malignancies. Invariant natural killer T (iNKT) cells are innate-like T cells that, upon activation by lipids such as αGC, participate in antitumor immune surveillance. However, whether mediators of stress impact iNKT cell functions in this context remains unexplored. Here, we subjected mice to prolonged psychological stress due to physical restraint or chronic stress due to heterotypic stressors before administering αGC. We report that stress abrogates TH1-type cytokine production by iNKT cells in vivo, an effect that is reversible by glucocorticoid receptor (GR) blockade and that is diminished in mice selectively lacking GRs in their T cell compartment. Instead, iNKT cell responses are skewed towards an abnormal anti-inflammatory and TH17-type cytokine signature. Gene expression analysis revealed that iNKT cells in stressed mice express reduced levels of critical genes supporting their typical differentiation states. Accordingly, iNKT cells in stressed mice fail to protect against pulmonary metastases of B16-F10 melanoma and are also unable to initiate killing activity against MHC class I-deficient splenocytes in vivo or YAC-1 lymphoma cells in vitro. Finally, the suppressive effects of stress on iNKT cells are not due to their apoptotic death. Unlike conventional T cells, human and mouse iNKT cells are remarkably resistant to glucocorticoid-induced apoptosis. Collectively, our findings define a novel mechanism of stress-induced immunosuppression involving innate-like but not conventional T cells.