Fc-gamma receptor III shedding by polymorphonuclear cells in primary Sjögren's syndrome

A sandwich enzyme-linked immunosorbent assay was developed to assess Fc-gamma receptor III (Fc gamma RIII), based on a combination of two non-competing monoclonal antibodies. This receptor was detectable in the serum of eight out of 23 patients with primary Sjögren's syndrome and two out of 23 normal controls. The proportion of Fc gamma RIII-carrying polymorphonuclear (PMN) cells was lower (P < 0.05) in the patients with cell-free Fc gamma RIII (90.4 +/- 7.5%) than in the remainder (84.8 +/- 8.3%). The PMN cell functions were evaluated and the diminished adherence (71.7, geometric mean) and chemotaxis (1.23) paralleled the Fc gamma RIII release. The relative inefficiency of PMN cells in SS might be due to phagocytosis of immune complexes.