Comparison of the presence of immune complexes in Felty's syndrome and rheumatoid arthritis.

Evidence has been found to document the presence of circulating immune complexes in all patients with Felty's syndrome. The sera of all 12 patients studied showed intermediate complexes by analytical ultracentrifugation. The sera of 9 of 12 patients (75%) showed precipitin lines upon immunodiffusion against IgM rheumatoid factor. Both findings were statistically increased above those in a matched group of patients with classic rheumatoid arthritis. The presence of circulating immune complexes in the sera of the Felty patients was consistent with the observation that large inclusions containing IgG, IgM, and complement were phagocytized by normal polymorphonuclear cells when incubated with sera of Felty patients. Normal polymorphonuclear cells phagocytosed inclusions from 77% of Felty sera, compared with 27% classic rheumatoid arthritis sera. It is suggested that the uptake of immune complexes by polymorphonuclear cells plays a role in the neutropenia of Felty's syndrome.