Invariant natural killer T (iNKT) cells are innate-like lymphocytes that rapidly respond to lipid antigens presented by CD1d or to inflammatory cytokines and influence diverse immune responses. Much of our current understanding of iNKT cell biology derives from murine studies, which established a framework of thymic differentiation into NKT1, NKT2, and NKT17 subsets. Recent single-cell RNA sequencing (scRNAseq) studies have substantially expanded this view by revealing non-linear developmental trajectories, early epigenomic priming, and a multipotent recent thymic emigrant population that continues to differentiate after thymic egress. In peripheral tissues, iNKT cells undergo extensive remodeling driven by local environmental cues and antigen exposure, giving rise to regulatory, and effector states not observed in the thymus. At the same time, emerging human studies reveal principles that differ from those described in mice. Human iNKT cells exhibit a blended type 1/type 17 transcriptional program, limited evidence for NKT2-like populations, and functionally distinct CD4+, double-negative (DN), CD8αα+, and terminal effector-like subsets. Comparative analyses across species further suggest that differences in thymic selection, transcription factor networks, and peripheral maturation contribute to divergent patterns of iNKT cell specialization. Together, these findings support a revised view of iNKT cells as dynamic and context-dependent transcriptional states shaped by developmental history, tissue environment, antigen exposure, and species-specific regulatory programs.
Meng Zhao, Lihua Wu· Frontiers in Immunology· 0 citations
Invariant natural killer T (iNKT) cells are innate-like T cells with rapid effector functions. Distinct metabolic programs support their differentiation and function. We found that iNKT cells exhibit higher mitochondrial content, activity, and a punctate morphology compared to conventional CD4+ T cells. Notably, the mitochondrial fusion regulator Opa1, but not the fission factor Drp1, is specifically required for iNKT cell differentiation: NKT1 and NKT17 subsets are markedly reduced in Opa1-deficient mice, whereas NKT2 cells remain unaffected.
We used complementary approaches, including conditional genetic models, flow cytometry, thymic organ culture, confocal imaging, and transcriptomic analyses, to dissect how mitochondrial dynamics influence iNKT cell development and signaling.
The differentiation defect is cell-intrinsic and not rescued by Bcl-XL overexpression. Opa1 loss leads to increased mitochondrial volume and decreased membrane potential, indicating dysfunction supported by transcriptional changes. Metabolic reprogramming accompanies this defect, with increased Glut1 expression and 2-NBDG uptake, while LDHA appears to compensate for Opa1 loss. TCR signaling is impaired: NF-κB, AP-1, and mTOR activities are reduced, whereas PLZF and Egr2, downstream of Ca²+/NFAT, are elevated. Consistently, TCR-induced Ca²+ flux is altered. Remarkably, simultaneous loss of Opa1 and Drp1, which induces mitochondrial stasis, partially restores iNKT cell homeostasis, proliferation, and TCR signaling in Opa1-deficient cells.
These findings uncover a critical role for Opa1-mediated mitochondrial dynamics in coordinating TCR signaling and metabolic programs that shape iNKT cell differentiation.
NIH
Hematopoiesis and Immune System Development (HEM)
Meng Zhao, Jianan Cheng, Xiao-Hui Sun et al.· Journal of Immunology· 0 citations