De novo steroidogenesis maintains female‑specific Th2 identity and constrains effector function

ABSTRACT Background T helper 2 (Th2) lymphocytes orchestrate type-2 immunity and drive allergic diseases that disproportionately affect females. Sexual dimorphism in Th2 responses is well-documented, yet current models attribute sex differences exclusively to circulating gonadal hormones and sex chromosomes. Whether cell-intrinsic steroidogenesis, mediated by the enzyme Cyp11a1, contributes to female-biased Th2 differentiation and function remains unknown. Methods Transcriptomes of in vitro generated Th2 cells from male and female T cell-specific Cyp11a1 -knockout ( Cyp11a1 fl/fl ; Cd4 Cre ) and control ( Cyp11a1 fl/fl ) mice were compared. Differential expression, hallmark pathway analysis, transcription factor activity scoring, and functional assays were performed across sexes and genotypes. Cyp11a1-dependent differentially expressed genes were integrated with sex-stratified human Th2 transcriptomes obtained from the type-2 inflammatory skin disease atopic dermatitis. Results Cyp11a1 deletion markedly reduced the transcriptional signature distinguishing female from male Th2 cells. Female Cyp11a1 -knockout Th2 cells underwent extensive transcriptomic reprogramming converging toward the male profile, while male cells were largely unaffected. Female-specific pathway changes included reduced inflammatory signatures and enhanced cell-cycle programmes. Functionally, female Cyp11a1 -deficient Th2 cells exhibited significantly increased proliferation and elevated IL-13 production; male knockout cells showed no comparable changes. These effects were developmentally stage-specific, emerging during Th2 differentiation but not in naïve precursors. Cross-species analysis identified a conserved gene module shared between Cyp11a1 -deficient female mouse Th2 cells and female-biased human Th2 cells in atopic dermatitis. Conclusions Cyp11a1-mediated steroidogenesis is a cell-intrinsic regulator of the female-biased Th2 transcriptional and functional state, identifying de novo steroidogenesis as a mechanism of immunological sexual dimorphism with direct relevance for female-predominant allergic disease.