Psoriatic patients with arthropathy show significant expression of free HLA class I heavy chains on circulating monocytes: a potential role in the pathogenesis of psoriatic arthropathy

BACKGROUND: Surface free heavy chains on monocytes were recently implicated in playing a role in the pathogenesis of several forms of arthritis. OBJECTIVES: To determine the expression of surface free heavy chains (recognized by monoclonal antibody HC10) on peripheral blood mononuclear cells of psoriatic patients with or without arthropathy. METHODS: Twenty-eight psoriatic patients from the dermatology outpatient clinic were included in this study. Blood samples were collected during outpatient visits and clinical characteristics of the patients were documented. Quantitative analyses of circulating mononuclear cells were performed using flow cytometry. RESULTS: Circulating monocytes showed higher expression of HC10 compared with circulating lymphocytes (P < 0.05). Psoriatic patients with arthropathy showed elevated expression of HC10 on peripheral blood monocytes compared with those without arthropathy (P < 0.05). Among the arthropathic group, those without the human leucocyte antigen (HLA)-B27 allele showed even higher expression of HC10 on circulating monocytes compared with those possessing HLA-B27 (P < 0.05). The polyarthropathic subgroup showed the highest HC10 expression, but the level of expression was not high enough to be of statistical significance compared with other arthropathic subgroups. No correlation was found between psoriatic skin involvement and the expression of HC10 on circulating monocytes. CONCLUSIONS: The presence of free heavy chains on circulating monocytes is closely associated with psoriatic arthropathy, while the expression of free heavy chains on circulating monocytes has no significant influence on psoriatic skin lesions.