Characterization of CD200-Receptor Expression in the Murine Epidermis

CD 200 is a widely expressed transmembrane glycoprotein that transmits an inhibitory signal after ligation of the structurally homologous CD 200-receptor-1 (CD 200 R1). Recently, we showed that CD 200 is expressed on keratinocytes and plays a role in protecting hair follicles from autoimmune attack. Here, we report the characterization of cell surface and mRNA expression of CD 200 R1 by cells of the murine epidermis. In addition, we report mRNA expression for other members of the CD 200 R-family (R2-R4) by quantitative real-time RT-PCR. Variable levels of CD 200 R1, R2, R3, and R4 mRNA were detected in bulk epidermal cell suspensions. Freshly isolated Langerhans cells (LC) preferentially expressed CD 200 R1. Consistent with an inhibitory role for CD 200:CD 200 R1 interaction, LC obtained from mice deficient in CD 200 (CD 200(-/-)) were in a heightened state of activation as compared with wild-type (CD 200(+/+)) cells. Freshly isolated dendritic epidermal T cells (DETC) expressed low levels of CD 200 R1, R2, and R3 mRNA, but they preferentially increased cell surface and mRNA expression of CD 200 R1 upon activation in vitro. In functional assays using sub-optimal CD3 signaling, immobilized CD 200 inhibited DETC proliferation and cytokine secretion. Collectively, these results suggest that CD 200:CD 200 R interactions may play a role in regulating both LC and DETC in cutaneous immune reactions.