Phagocytosis by normal polymorphonuclear leukocytes of immune complexes from serum of patients with Felty's syndrome and rheumatoid arthritis with special reference to IgE immune complexes.

Sera from patients with Felty's syndrome, rheumatoid arthritis (RA) and controls were investigated for the presence of immune complexes (IC) using phagocytosis by normal polymorphonuclear leukocytes and direct immunofluorescence technique. IC visible as large cytoplasmic inclusions were seen in 19 of 24 cases of Felty's syndrome, 3 of 16 cases of RA, and all 3 patients with extraarticular manifestations, and none of 21 control sera. IC containing IgG, IgA and complement C3 were found in nearly all positive cases. IgM IC were found in only 8 of the Felty's syndrome cases, IgE in 5 and beta-2-microglobulin in one case, respectively. A tendency to increasing number of large inclusion positive cells in vitro was found inversely correlated to the number of circulating leukocytes in the Felty patients at the time of serum sampling. In contrast, small cytoplasmic inclusions were found both in Felty's syndrome and RA patients and in some of the controls, and IgG and C3 were the most frequent constituents in these cases. As these inclusions were found in all groups it may have little significance. IgE IC as determined by a PEG precipitation technique were positive in the same 5 cases of Felty's syndrome with IgE containing inclusions, and in one case of RA with extraarticular manifestations. The complexed IgE amounted to about 3% of the total serum concentration of IgE. Phagocytosed IC may be involved in the pathogenesis of neutropenia and contribute to the inflammatory processes in Felty's syndrome.