Natural killer (NK) cells at inflammatory sites of patients with rheumatoid arthritis and IgM rheumatoid factor positive polyarticular juvenile rheumatoid arthritis.

NK cell activity and Leu 7+ cells were determined in mononuclear cells (MNC) from patients with rheumatoid arthritis (RA) and IgM rheumatoid factor positive polyarticular juvenile rheumatoid arthritis (JRA). NK cell activity was measured in a 51Cr release assay and the Leu 7 positive cells were enumerated in indirect immunofluorescence. The mean NK cell activity +/- SEM was reduced in MNC from peripheral blood (PB), synovial fluid (SF) and synovial membranes (SM's) of patients with RA, with the values of 19.5 +/- 1.4 (p less than 0.00003), 18.3 +/- 3.1 (p less than 0.009) and 2.9 +/- 0.5 (p less than 0.0003) respectively, compared with 26.1 +/- 1.4 in MNC from the PB of healthy controls. The mean percentages of Leu 7 positive cells in MNC from PB and SF on patients with RA were normal while the mean percentage of Leu 7+ cells in MNC eluted from SM's was significantly reduced as compared to that of MNC from PB of healthy controls (p less than 0.0006). In JRA similar results concerning NK activity and Leu 7 positive cells were found but the number of experiments was too low for statistical analysis. MNC from the SF, in contrast to that of BP and SM, had a significant cytotoxicity against the Raji cell line which is a non-NK cell target.