Spatiotemporal regulation of human IFN-ε and innate immunity in the female reproductive tract

Although published studies have demonstrated that IFN-ε has a crucial role in regulating protective immunity in the mouse female reproductive tract, expression and regulation of IFN-ε in the human female reproductive tract (hFRT) have not been characterized to our knowledge. We obtained hFRT samples from a well-characterized cohort of women to enable us to comprehensively assess ex vivo IFN-ε expression in the hFRT at various stages of the menstrual cycle. We found that among the various types of IFNs, IFN-ε was uniquely, selectively, and constitutively expressed in the hFRT epithelium. It had distinct expression patterns in the surface and glandular epithelia of the upper hFRT compared with basal layers of the stratified squamous epithelia of the lower hFRT. There was cyclical variation of IFN-ε expression in the endometrial epithelium of the upper hFRT and not in the distal FRT, consistent with selective endometrial expression of the progesterone receptor and regulation of the IFNE promoter by progesterone. Because we showed IFN-ε stimulated important protective IFN-regulated genes in FRT epithelium, this characterization is a key element in understanding the mechanisms of hormonal control of mucosal immunity.