CELL-FREE FC-GAMMA RECEPTOR III IN SERA FROM PATIENTS WITH SYSTEMIC LUPUS-ERYTHEMATOSUS - CORRELATION WITH CLINICAL AND BIOLOGICAL FEATURES

Fifty patients (41 females and 9 males, ranging in age from 12 to 79 y ears) with systemic lupus erythematosus (SLE) and 20 normal controls w ere evaluated for the presence of plasma cell-free Fc gamma receptor I II (Fc gamma RII) using an ELISA based upon a sandwich of two monoclon al antibodies. The standard curve was obtained with serial dilutions o f recombinant Fc gamma RIII. In the patients, the cell-free Fc gamma R III levels ranged from to 1.76 mu g/ml, while it did not exceed 0.21 m u g/ml in the controls. Assuming that the cutoff is 0.25 mu g/ml, 11 S LE patients and no controls had elevated cell-free Fc gamma RIII level s in the serum. Among the SLE patients, the level of cell-free Fc gamm a RIII was significantly lower (p=0.05) in 4 patients with sicca syndr ome than in the remaining 46. Furthermore, cell-free Fc gamma RIII lev els appeared to be lower in 11 patients with renal involvement than in those without. For the biological parameters, we observed that the 27 patients who presented lymphopenia also had a lower level of cell-fre e Fc gamma RIII when compared to the 23 patients without lymphopenia ( 0.09+/-0.19 versus 0.35+/-0.52 mu g/ml; p=0.05). Circulating cell-free Fc gamma RIII may originate from shedding by presumably activated pol ymorphonuclear cells.