Adhesion molecule expression in synovial membrane obtained from patients with psoriatic arthritis (PA) has previously been compared with rheumatoid arthritis (RA).(1) Although expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) was similar in both psoriatic and rheumatoid synovium, in contrast, little or no endothelial leucocyte adhesion molecule-1 (ELAM-1) was observed in psoriatic synovium. In the present study, the expression of ICAM-1, ELAM-1 and VCAM-1 was examined in the involved and uninvolved skin from patients with PA (n = 15), patients with psoriasis (Ps) but no arthritis (n = 5) and in normal skin (n = 4). ICAM-1 was intensely expressed on endothelium and keratinocytes of involved skin from patients with Ps with or without arthritis. There was constitutive expression of ICAM-1 on endothelium only in uninvolved and normal skin. In contrast, ELAM-1 expression was restricted to endothelial cells; it was widespread and intense in involved skin, but was minimal in uninvolved and normal skin. VCAM-1 was expressed on endothelium, and also on some dendritic cells in involved psoriatic skin. There was minimal VCAM-1 staining on endothelial cells in uninvolved and normal skin. In conclusion, in involved psoriatic skin from patients with and without arthritis ICAM-1, ELAM-1 and VCAM-1 expression is up-regulated on vascular endothelium, and ICAM-1 is expressed on keratinocytes. However, ELAM-1 and VCAM-1 expression seen in dermal vessels is not found in psoriatic synovial vessels. These differences suggest a mechanism for controlling cellular traffic in Ps and in PA.
