In situ detection of retinoid-X receptor expression in normal and psoriatic human skin

Summary Increasing evidence suggests that the retinmd-X receptors RXR(-α,-β-γ) play a crucial part in regulating the transcription a I activity of several steroid hormone receptors, including 1.25-dihydroxyvitamin D3 receptors (VDR) and retinoic acid receptors (RAR-α,-β,-γ). We developed a new technique for immunohistochemical in situ detection of RXR receptors, and investigated the localization of RXR-a in normal and psoriatic human skin using a recently raised corresponding specific antibody. RXR-α positive cells related to the skin were phenotyped by sequential sections and a double-labelling procedure for the simultaneous demonstration of this nuclear receptor and cell membrane antigens, as well as cytokeratin 10. HLA-DR and vimentin. Our findings indicate that: (i) RXR-m is strongly expressed in normal and psoriatic human skin: (ii) most of the cell types in normal human skin, including keratinocytes, melanocytes, fibroblasts andskin immune cells such as Langerhans cells, reveal strong nuclear immunoreactivity for RXR-a, with less cytoplasmic staining; (Hi) altered levels or distribution of RXR-n in the skin do not appear to be involved in the genesis of psoriasis vulgaris, but subepidermal and subcellular distribution suggest a function of RXR-α in the transition from proliferation to differentiation in epidermal keratinocytes: (iv) expression in the hair follicle points to a contribution from RXR-α to hair growth.