Possible role of natural killer cells in granulomatous inflammation

Natural killer (NK) cell activity is down-regulated in patients with active chronic inflammatory processes, and appears abnormal in sarcoidosis. We investigated NK cell activity in lymph nodes (LN) and spleen cells of C57BL/6 mice by using a 51Cr-release assay against Yac-1 tumor target cells. Hepatic granulomas were caused by infection with 75 cercariae of Schistsoma mansoni ans skin granulomas formed by transplanting isolated liver granulomas into skin of another group of naive mice. Also, anti-NK-1.1 MoAb was injected intraperitoneally into some mice (1 mg IgG/mouse) 1 wk before and weekly for 4 wks after grafting; control mice received saline. Well-organized granulomas appeared in both liver and skin. NK activity (%) was markedly reduce in LN and spleen: (table; see text) The results showed a relationship between granuloma formation and reduction of NK cell activity; both systemically and locally. MoAb did not alter total LN and spleen cell numbers, but reduced NK cell activity by 70-90%. Mean diameter of skin granulomas developed in treated mice was greater (p less than 0.05). NK cells may act as suppressor cells in granulomatous inflammation.