ELEVATED LEVELS OF CIRCULATING INTERCELLULAR-ADHESION MOLECULE-3 (CLCAM-3) IN PSORIASIS

Intercellular adhesion molecule (ICAM)-3 is important in regulating le ukocyte function and T-lymphocyte-antigen presenting cell interactions . Soluble, circulating forms of ICAM-3 and ICAM-1 (cICAM-3, cICAM-1) e xist in serum, and levels are elevated in a variety of autoimmune dise ases. Two types of soluble circulating tumour necrosis factor receptor (cTNF-R1, cTNF-R2) are found in the sera of healthy people. cTNF-R1 b inds TNF-alpha and is important in regulating TNF-alpha-mediated infla mmation. Psoriasis is a T-lymphocyte-mediated disease, characterized b y cutaneous expression of ICAM-1, ICAM-3 and TNF-alpha. As it is unkno wn whether cICAM-3 is increased in sera of patients with psoriasis, we measured serum levels of cICAM-3 and compared them to levels of cICAM -1, cTNF-R1 and clinical severity of psoriasis. Sera was taken from 11 2 healthy controls and 32 patients with psoriasis. Clinical severity o f psoriasis was assessed using the psoriasis area severity index (PASI ). cICAM-1, cICAM-3 and cTNF-R1 in serum were quantitated using a dual antibody, solid phase ELISA. Levels of cICAM-3, cICAM-1 and cTNF-R1 w ere significantly increased in sera of patients with psoriasis as comp ared with controls, and these elevated levels correlated with clinical severity of psoriasis as assessed by the PASI. Also, there were good correlations between serum levels of cICAM-3, cICAM-1 and cTNF-R1 in p soriasis. These results demonstrate, for the first time, that circulat ing levels of cICAM-3 are increased in psoriasis and that these levels correlate both with disease severity and with elevated levels of cICA M-1 and cTNF-R1. The exact physiologic roles of circulating, soluble a dhesion molecules and cTNF-R1 are unknown, but it is hypothesised that elevation of their circulating levels, as observed in psoriasis, may play a role in modulating the inflammatory reactions occurring in this disease.