Coordinated transcriptional and epigenetic regulation of type 2 CD8⁺ T cells in asthma

Steroid-insensitive type 2 cytokine-producing CD8⁺ T cells (Tc2) are enriched in patients with severe asthma and correlate with disease severity, highlighting their potential role as drivers of treatment-refractory disease. The molecular mechanisms governing their functional differentiation remain incompletely understood.

Mouse CD8⁺ T cells were differentiated in vitro under type 1 or type 2 polarizing conditions. Genome-wide transcriptional and H3 histone acetylation profiles were analyzed using RNA sequencing and chromatin immunoprecipitation (ChIP) sequencing. Both were integrated to identify H3Ac-associated transcriptional programs. Functional consequences of pharmacologic inhibition of histone acetyltransferase (HAT) activity in Tc2 cells were assessed after adoptive transfer into allergen-sensitized CD8-deficient mice. In parallel, transcriptomic profiling of human CD8⁺ T cells from healthy individuals and steroid-resistant asthmatics was performed and integrated with the mouse Tc2 dataset to identify conserved regulatory pathways.

Tc1 and Tc2 differentiation were characterized by coordinated transcriptional remodeling with distinct type 2-associated networks emerging in response to IL-4 and T cell receptor stimulation including Il-24, Cyp11a1, and Il-13. Integration of histone acetylation data and transcriptional networks identified condition-specific H3Ac-associated differentially-expressed genes (DEGs) and functional programs specific to Tc1 and Tc2 cells. While H3Ac-associated DEGs in Tc1 cells were linked predominantly to broader inflammatory and immune effector pathways, this integrative approach showed an enrichment of type 2 immune pathways in Tc2 cells. Pharmacologic modulation of HAT activity increased Tc2 cytokine responses and enhanced the pathogenic effects of Tc2 cells in vivo, resulting in heightened airway hyperresponsiveness and eosinophilic inflammation. Human CD8⁺ T cells from steroid-resistant asthmatics exhibited distinct transcriptional profiles compared with healthy individuals, including increased IL-13 expression. Cross-species integration revealed significant overlap between mouse Tc2 transcriptional signatures and gene networks in steroid-resistant asthmatics.

These findings propose coordinated epigenetic and transcriptional remodeling as a central mechanism regulating functional differentiation of Tc2 cells. They further define shared molecular pathways linking CD8⁺ T cell programming to type 2 inflammation in severe asthma, providing insight into mechanisms that may contribute to persistent disease and therapeutic resistance.