Enhanced bacterial phagocytosis by peripheral blood monocytes in rheumatoid arthritis.

To assess the functional state of peripheral blood monocytes in rheumatoid arthritis, we have measured phagocytosis of Staphylococcus aureus and Proteus mirabilis in 48 patients and 28 controls. Using radiolabelled bacteria preopsonised in normal human serum we have demonstrated significantly enhanced uptake of both organisms by patients' monocytes: (Median % uptake Staph. aureus: patients = 35.8; controls = 19.3; p less than 0.001. Median % uptake P. mirabilis: patients = 32.3; controls = 19.8; p less than 0.01.) These results indicate that patients' monocytes exist in an activated state, which may be important in the pathogenesis of rheumatoid arthritis.