Natural killing (NK) of cytomegalovirus (CMV)‐infected fibroblasts: A comparison between two strains of CMV, uninfected fibroblasts, and K562 cells

Spontaneous cytolysis of uninfected human fibroblasts (HF), K562 cells, and HF cells infected with cytomegalovirus (CMV) was associated with nonadherent peripheral blood leukocytes (PBL) that passed through a nylon wool column, and rosetted with sheep erythrocytes at low affinity; cytolysis was further associated with enriched preparations of large granular lymphocytes (LGL). The Leu‐7 marker did not correlate as a cell phenotype with functional activity in normal donors. The HF cells infected with the AD169 strain of CMV were as sensitive to cytolysis as K562 cells, although the kinetics of cytolysis differed; HF cells infected with the Davis strain of CMV were generally less sensitive to cytolysis than uninfected fibroblasts. Equivalent amounts of interferon were detected in NK assays containing Davis targets, AD169 targets, or K562 cells; interferon was not detected in NK assays of HF cells. Neither uninfected nor infected HF cells competed effectively against 51 Cr‐labeled K562 cells in cold competition experiments; K562 cells, however, competed effectively against 51 Cr‐labeled AD169‐CMV targets. Uninfected HF cells were efficient competitors of AD169‐CMV targets. Davis‐CMV‐infected cells were less effective, however, than uninfected HF cells in competition experiments, suggesting that fewer receptors for NK cells were present on these targets.