Tyrosine phosphorylation in neutrophils from synovial fluid of patients with rheumatoid arthritis.

The priming of neutrophils is associated with an increase in the level of tyrosine phosphorylation of cytosolic proteins, specifically of proteins with mol. wts of 42 and 74 kDa. We show here, using dot blots and Western blotting, that neutrophils isolated from rheumatoid synovial fluid have increased tyrosine phosphorylation of these target proteins. The level of tyrosine phosphorylation within neutrophils in the synovial fluid was increased when compared with neutrophils from the blood of the same patients, normal blood or neutrophils from the synovial fluid of patients without rheumatoid arthritis. Neutrophils from the rheumatoid synovial fluid were also more active and were unable to be further primed by exogenous primers. These data suggest that this elevation of tyrosine phosphorylation was the result of the action of local priming agents within the rheumatoid synovial fluid.