Suppression of natural killer cell activity by Friend murine leukemia virus.

BALB/c mice infected with Friend murine leukemia virus (F-MuLV) evinced a decreased natural killer (NK) cell activity to susceptible target cells. This suppression increased as the interval between infection and assay was lengthened. The decrease in NK activity due to F-MuLV infection was partially reversible when spleen cells were pretreated with interferon before the cytolytic assay. The ability of F-MuLV-infected splenocytes to bind to target cells was unaltered, indicating that the defect was in the lytic phase of NK cytolysis. When mixed with uninfected spleen cells, F-MuLV-infected splenocytes suppressed their NK cell activity. This suppression was associated with a nylon wool-adherent cell population in the F-MuLV-infected spleens.