[IgG rheumatoid factor in rheumatoid arthritis with interstitial lung disease].

Case of rheumatoid arthritis (RA) with interstitial lung disease (ILD) have been reported to show increased titers of rheumatoid factor (RF) in serum; however the pathogenic role of this substance in the lung is still obscure. The aims of this study were to estimate IgGRF in the bronchoalveolar lavage fluid (BALF) in RA and to investigate its possible roles in the ILD of RA. Two step bronchoalveolar lavage in 20 RA patients (9 males, 11 females) was performed in conjunction with high resolution chest CT. IgGRF was measured by enzyme-linked immunosorbent assay and its molecular size in BALF was evaluated by high performance liquid chromatography. IgGRF bound to BALF cells was eluted by sonication of the cells. RA patients with ILD had significantly elevated levels of IgGRF in serum as well as in BALF. The IgGRF in BALF was monomeric in 2 of 3 RA patients with ILD. The activity of IgGRF bound to BALF cells was significantly higher in RA with ILD than in control patients. These findings suggest that monomeric IgGRF in the lungs of RA patients could bind to the cells with Fc receptors.