Immunosuppression by Leukemia Viruses

Abstract

Summary Infection of adult BALB/c mice with Friend disease virus resulted in a marked alteration of the expected immune response to a second injection of sheep erythrocytes. Whereas normal control mice primed 4 weeks previously with sheep erythrocytes had a vigorous cellular and humoral immune response following a second injection of erythrocytes, mice infected with FDV before the booster injection had a markedly suppressed response. Both high- and low-efficiency hemolysin-forming cells, presumably due to 19 S IgM and 7 S IgG antibody, respectively, were depressed in spleens of infected mice. The appearance of 7 S PFC's was suppressed to the greatest extent. Infection of mice with virus and antigen at the same time resulted in only a slight to moderate suppression in the number of antibody-forming cells appearing 4 days later, the day of peak response. However, by the 7th to 10th day after immunization and virus infection there was a marked depression in the number of cells forming both 7 S or 19 S plaques. When mice were injected with erythrocytes 1 month after primary immunization, and then infected with virus 2 days later, there was a stimulation in the number of 19 S and 7 S PFC's 2 days later (4th day after secondary immunization). However, by the 7th to 10th day most of the infected mice had fewer 7 S PFC's than did the controls. Splenomegaly was generally evident at this time. Serum antibody titers in secondarily immunized mice were only slightly affected, if at all, when mice were infected with FDV either simultaneously or after immunization. Infection 3 days before immunization had a slight effect on antibody titers, whereas infection 8 days before immunization generally resulted in a significant depression. Most of the serum antibody was resistant to 2-ME treatment before and after secondary immunization, both in control and infected animals, suggesting that much of the antibody was 7 S IgG.