Synovial fluid polymorphonuclear leucocytes from patients with rheumatoid arthritis have reduced MPO and NADPH-oxidase activity.

Synovial fluid (SF) polymorphonuclear leucocytes (PMN) from patients with rheumatoid arthritis (RA) were compared to RA and normal circulating blood PMN. RA SF PMN were as viable as blood PMN and remained viable for up to 24 h in culture. Measurement of myeloperoxidase indicated that RA SF PMN had degranulated and secreted their myeloperoxidase prior to isolation, 26.5 +/- 11.7% being found extracellularly compared to less than 2.9% in RA and normal blood PMN. RA SF PMN alone showed a decrease in basal NADPH-oxidase activity as well as an increase in responsiveness to stimulation by chemotactic peptide during culture. Stimulation of PMN with phorbol-12-myrisitate-13-acetate evoked equivalent responses in each population before and after culture. These results demonstrate a major difference in resting and receptor-mediated activation of superoxide release by RA SF PMN. Together, these results have important implications in identifying the role of the activated PMN in RA.