IL-10 inhibits ICAM-1 expression on human Langerhans cells but not on keratinocytes, dermal endothelial cells or fibroblasts.

Intercellular adhesion molecule-1 (ICAM-1) is regularly expressed or inducible on all major cutaneous cell populations including Langerhans cells, keratinocytes, endothelial cells and dermal fibroblasts. ICAM-1 is induced in the skin under inflammatory conditions and plays an important role in the activation of T cells. Interleukin-10 (IL-10) is a pluripotent immunosuppressive cytokine that inhibits proliferation of T cells via inhibition of antigen-presenting cells including Langerhans cells. We demonstrates that IL-10 inhibits baseline and also cytokine-stimulated ICAM-1 expression on human Langerhans cells, which has previously been shown in the murine system. No effect of IL-10 was seen on human dermal vascular endothelial cells, which like Langerhans cells are also able to present antigen. Additionally, no inhibitory effect of IL-10 was observed on the ICAM-1 expression of keratinocytes and dermal fibroblasts. As IL-10 only weakly suppresses MCH II on human Langerhans cells, inhibition of ICAM-1 and other accessory molecules by IL-10 seems to be an important mechanism inhibiting the antigen-presenting function of human Langerhans cells.