Immune complexes (IC) are frequently detected in patients with rheumatoid vasculitis (RV). To explore the pathogenic role of IC in the development of vasculitis among patients with rheumatoid arthritis (RA), we examined the effect of IC on the expression of cell adhesion molecules (CAM) on polymorphonuclear cells (PMN).
PMN from healthy volunteers were incubated with the sera from 26 patients with RA including 9 patients with RV, and the expression of CAM on the PMN was assessed by flow cytometry.
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 expression. On the other hand, 89% (8/9) of the samples from RV patients and 12% (2/17) of the samples from RA patients without RV revealed up-regulated CD18 expression. However, the expression of CD11a was not affected. Up-regulation of CD11b and CD18 on PMN was also induced by the immunoglobulin G (IgG) 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 changes in CAM expression on PMN induced by IgG of RV patients were not observed when PMN were incubated with the IgG of RV patients from which the IC formed by IgG had been removed.
These results suggest that IC formed by IgG in patients with RA are involved in the development of vasculitis by affecting the expression of CAM on PMN.