Reduction of TLR7/8-Induced IFN-I Responses by Plasmacytoid Dendritic Cells in a Longitudinal Cohort of Trans Men
Type I interferons (IFN-I) are important mediators of antiviral immunity and autoimmune diseases. Plasmacytoid dendritic cells (pDCs) from females exert an elevated capacity to produce IFN-I in response to activation of toll-like receptor 7 (TLR7) compared to male pDCs, and both hormones and genes encoded by the X chromosome have been implicated in these sex-specific differences. Using longitudinal samples collected from a cohort of trans men receiving testosterone injections as gender-affirming hormone therapy (GAHT), the impact of testosterone on TLR7-mediated IFN-I production by pDCs was assessed. GAHT induced testosterone and estradiol levels within male reference ranges and increased hemoglobin and hematocrit levels, demonstrating biological activity of testosterone. scRNA seq of pDCs showed downregulation of IFN-I-related gene expression signatures, but also revealed inter-donor heterogeneity on the transcriptional level. Longitudinal quantification of IFN-I protein production by pDCs following TLR7-stimulation showed significant and continuous reduction of IFN-I production in trans men, and reduced expression of IFN-I-stimulated genes. These longitudinal studies in trans men demonstrate that testosterone can reduce IFN-I production by pDCs, and provide novel insights into the immune-modulatory role of testosterone in sex differential IFN-I-mediated immune responses. Overall design: Plasmacytoid DCs (pDCs) from longitudinal blood samples collected from a cohort of trans men receiving testosterone injections as gender-affirming hormone therapy (GAHT) were used in this study. PBMCs were stimulated with CL097 and pDCs were FACS-isolated following single-cell sequencing (10x Genomics) including TotalSeq Hashtag antibodies to combined different treatment conditions per donor.