Effect of immune complexes in serum from patients with rheumatoid vasculitis on the expression of cell adhesion molecules on polymorphonuclear cells

Objective Immune complexes (IC) are frequently detected in patients with rheumatoid v asculitis (RV). To explore the pathogenic role of IC in the development of vasculitis among patients with rheumatoid arthritis (RA), we examined the e ffect of IC on the expression of cell adhesion molecules (CAM) on polymorph onuclear cells (PMN). Methods PMN from healthy volunteers were incubated wi th the sera from 26 patients with RA including 9 patients with RV and the e xpression of CAM on the PMN was assessed by flow cytometry. Results We found that 67% (6/9) of the serum samples from RV patients and 18% (3/17 ) of the samples from RA patients without RV revealed up-regulated CD11b ex pression. On the other hand 89% (8/9) of the samples from RV patients and 1 2% (2/17) of the samples from RA patients without RV revealed up-regulated CD18 expression. However; the expression of CD11a was not affected. Up-regu lation of CD11b and CD18 on PMN was also induced by the immunoglobulin G (I gG) fraction of the sera of RV patients. Moreover L-selectin expression on PMN was down regulated by the sera or IgG of some patients with RV. These c hanges in CAM expression on PMN induced by IgG of RV patients were not obse rved when PMN were incubated with the IgG of RV patients from which the IC formed by IgG had been removed. Conclusion These results suggest that IC formed by IgG in patients with RA are involve d in the development of vasculitis by affecting the expression of CAM on PM N.