Correlation between natural killer cell activation in the bone marrow and haemopoietic dysfunction following cytomegalovirus infection of mice

We describe here the activation of natural killer (NK) cells in the bone marrows and spleens of mice infected with murine cytomegalovirus (MCMV). NK activity at these sites peaked at day 2 to 3 post-infection (p.i.) and declined between days 6 and 10 p.i. in BALB/c and C57BL/6 mice. In BALB/c mice, the increases in NK activity coincided with depletion of colony-forming units of the granulocyte-monocyte lineage (CFU-GM) from the marrow. CFU-GM depletion in MCMV-infected C57BL/6 mice was less severe, despite the presence of activated NK cells in the marrow. Treatment of BALB/c mice with anti-asialo GM, prior to MCMV infection resulted in less severe CFU-GM depletion at day 2 p.i. than infection with MCMV alone. When homozygous C57BL/6 or CBA/CaH bg/bg mice were infected with MCMV, depletion of marrow CFU-GM was more severe than in their heterozygous littermates. Finally, we observed some inhibition of colony formation when marrow cells from MCMV-infected and uninfected BALB/c donors were mixed and incubated prior to the CFU-GM assay. These results suggest that activated NK cells may contribute to depletion of haemopoietic cells soon after MCMV infection of BALB/c mice, but may limit the loss of these cells in C57BL/6 and CBA/CaH mice.