Impaired indomethacin-boosting of the defective natural killer cell activity in patients with primary Sjögren's syndrome.

As it has been shown that the natural killer (NK) cell activity is depressed and the prostaglandin (PG) metabolism is disturbed in patients with primary Sjögren's syndrome (primary SS), we examined the in vitro effect of indomethacin on the NK cell activity. The NK cell activity against K 562 target cells was measured in 20 female patients with primary SS and in 18 female normal controls matched for age. Blood mononuclear cells were incubated with indomethacin (1 microgram/ml). Median baseline NK cell activity in primary SS was 15.4% (range 5.8-50.4) versus 24.7% (range 6.2-47.4) in the controls (p less than 0.05). After in vitro exposure to indomethacin median NK cell activity in the patients was 21.2% versus 34.9% in the controls (p less than 0.02). Indomethacin-enhanced NK cell activity was significantly higher than baseline NK cell activity in both patients (p less than 0.05) and controls (p less than 0.01), but the NK cell activity of the patients was significantly less enhanced than that of the controls (p less than 0.02). We conclude that the impaired indomethacin-boosting of NK cell activity in patients with primary SS probably reflects a decreased capacity of blood mononuclear cells to produce PG in vitro.