Sex Hormone Receptor Expression in the Immune System

The major sex hormones that have been studied in immunity are estrogens, testosterone, progesterone, and vitamin D. Sex hormones bind to hormone receptors on the surface of immune cells or more classically, within the cytoplasm of the cell. Most immune cells express multiple sex hormone receptors that are involved in driving immune responses in sex-specific directions following antigen stimulation. Sex hormone regulation of innate antigen-presenting cells like dendritic cells, mast cells, and monocyte/macrophages is the key step in determining the type of adaptive immune response. Sex hormone receptors on adaptive T and B cells further distinguish sex differences in inflammation that characterize the immune response to infections and the development of chronic inflammatory diseases like autoimmune diseases. However, data are contradictory and further research is needed to better understand how sex hormone receptors regulate inflammation. This chapter describes current knowledge on how sex hormones alter the function of innate immune cells like dendritic cells, mast cells, macrophages, and adaptive immune cells like T cells, T regulatory cells, and B cells. Detailed descriptions of the downstream signaling pathways of major sex hormone receptors are also provided.