Production of neutrophil activating peptide-1 (NAP-1/IL-8) by blood and synovial fluid mononuclear cells from patients with arthritis.

As polymorphonuclear leukocytes (PMN) are predominant in inflammatory synovial fluids, we investigated the production of neutrophil-activating peptide-1 (NAP-1) by mononuclear cells (MC) from 15 synovial fluids and matched peripheral blood. MC were cultured for 24 h alone or with stimulants (ConA, LPS). NAP-1 was determined in the supernatants by a bioassay (elastase release from normal human PMN) and an immunoassay (sandwich ELISA with a mouse anti-NAP-1 mAb and an alkaline phosphatase labelled goat anti-NAP-1 pAb). The results showed a significant increase in NAP-1 production by synovial fluid MC when compared to peripheral blood MC. Both cell types produced more NAP-1 in the presence of added stimuli. The results obtained with the two methods of detection were in close agreement. No relationship was found between the amount of NAP-1 produced in 24 h and the number of synovial fluid leukocytes, the erythrocyte sedimentation rate, the diagnosis of the underlying arthritis or the treatment of the patients.