Natural killer cell activity during murine Schistosomiasis mansoni.

Natural killer cell (NK) activity of spleen cells from CBA/J and C57BL/6 mice infected with Schistosoma mansoni was assayed using 51Cr-labeled YAC-1 cells as target cells. No significant difference in NK activity was detected between infected and age-matched control spleen cells from 1 to 4 wk after infection. The NK-mediated cytotoxic abilities of both infected and age-matched control mice fell in parallel, as expected, on an age-related basis. However, on a cell-to-cell basis the splenic NK activity of mice infected from 8 to 18 wk was significantly less than that of age-matched control mice. Meanwhile, because of the splenomegaly associated with patent infection, the total number of nucleated splenocytes in chronically infected mice increased to fourfold that of age-matched control mice. Therefore, the total available NK activity per spleen was increased by chronic infection. The NK activities of spleen cells from age-matched control mice and those infected for 18 wk could be augmented by in vivo administration of polyinosinic-polycytidylic acid, indicating the continued responsiveness of NK cells from chronically infected mice to activation. Spleen cell NK activity in age-matched control and infected C57BL/6 mice exhibited a pattern similar to that of CBA/J mice.