Singh, S.; Nanjundappa, R. H.; Kolla, H. B.; S. Chauhan, D.; Palyada, A.; Krishnamurthy, P.; Umeshappa, C. S.

Invariant natural killer T (iNKT) cells are a unique subset of innate immune cells activated by T cell receptor (TCR) signaling through CD1d molecules presenting lipid antigens. By localizing to specific tissues, iNKT cells play critical roles in maintaining homeostasis and regulating pathophysiology, making them attractive therapeutic targets for inflammatory diseases. However, their frequency in the heart and potential roles in mitigating inflammation-induced cardiac damage remain poorly understood. In this study, we examined the distribution of cardiac iNKT subsets and their response to TCR-directed alpha Galactosyl ceramide/cluster of differentiation 1d (GalCer/CD1d) complexes in a mouse model of Doxorubicin (Dox)-induced cardiotoxicity. In healthy mice, the heart harbored distinct iNKT subsets, dominated by pro-inflammatory iNKT1 cells, followed by iNKT2 subsets. Treatment with GalCer/CD1d complexes preferentially expanded the iNKT1 subset. In Dox-induced cardiotoxicity, this treatment unexpectedly increased both IFN-{gamma}, a hallmark cytokine of iNKT1 cells, and IL-10, a key anti-inflammatory mediator typically associated with regulatory iNKT subsets. Despite the expansion of iNKT1 cells and elevated IFN-{gamma} levels, GalCer/CD1d treatment did not exacerbate cardiac damage and showed modest clinical improvements compared to controls. These findings highlight the complexity of iNKT-mediated immune regulation in the heart and emphasize the need for modified TCR-directed immunotherapeutics to skew immune responses toward a regulatory phenotype. Such approaches could hold promise for treating inflammatory cardiac diseases, including Dox-induced myocarditis, myocardial infarction, and autoimmune myocarditis.