Abstract
OBJECTIVE: To compare neutrophil Fc receptor (Fc gamma R) and CD59 signalling responses in normal healthy subjects and patients with active rheumatoid arthritis (RA). METHODS: Intracellular free calcium concentrations were measured in neutrophils loaded with the fluorescent calcium indicator fura-2, using a spectrofluorimeter. RESULTS: Basal intracellular calcium ion concentrations were similar in both groups when no primary antibody, CD59, or CD32 (Fc gamma RIII) antibody was added. When CD16 (Fc gamma RIII) antibody was added, there was a significantly greater basal calcium concentration in the patient group compared with the control group. Transient cytosolic calcium ion fluxes were observed after binding Fc gamma RII, Fc gamma RIII, or CD59 with specific monoclonal antibodies and cross linking with the F(ab)2 fragment of sheep antimouse IgG. Peak concentrations of intracellular free calcium, [Ca2+]i, after cross linking each of the three receptors, were comparable between normal healthy donors and patients with RA. The lag period between addition of cross linking antibodies and the increase in calcium was also similar between normal individuals and patients. CONCLUSION: Contrary to previous reports, these results demonstrate that Ca2+ signalling responses of cross linked Fc receptors in blood neutrophils from patients with RA are identical to those in neutrophils of normal subjects. Signalling responses of cross linked CD59 are also unaltered.