Increased C1q binding immune complexes in felty's syndrome

Abstract

Sera from patients with Felty's syndrome (FS) and rheumatoid arthritis (RA) were examined for the presence of circulating immune complexes (IC) by using the ¹²⁵I‐C1_q binding and monoclonal rheumatoid factor (mRF) techniques. Of 15 patients with FS, 9 (60%) had high ¹²⁵I‐C1_q binding as compared to 3 of 26 RA patients (12%). The average C1_q binding was significantly higher in the FS patients than in the RA patients without FS. C1_q binding in both FS and RA patients was significantly higher than a group of 90 normal controls. In addition, serum C4 levels were significantly lower in the FS patients than in the RA patients. In contrast to these findings, IC levels in FS and RA patients were very similar when measured by the mRF technique. These studies indicate that FS patients have higher levels of complement‐fixing IC in their sera than RA patients without FS. These findings raise the possibility that the complement‐fixing IC found in these patients may play a role in the pathogenesis of the neutropenia of FS.