T-lymphocyte subpopulations and function during murine cytomegalovirus infection

To study the effects of cytomegalovirus infection on T-lymphocyte subpopulations, we determined helper (Lyt 1.2) and suppressor (Lyt 2.2) T-lymphocyte subset numbers using monoclonal antibodies and measured lymphocyte responsiveness to mitogen during sublethal murine cytomegalovirus (MCMV) infection of 3-wk-old Balb/c mice. MCMV-infected mice had reduced Lyt 1.2 to Lyt 2.2 T-lymphocyte ratios on days 1, 3, 5, and 9 of infection. Alterations in T-lymphocyte subsets were accompanied by diminished lymphocyte response to concanavalin A. Lymphocyte responsiveness and Lyt 1.2 to Lyt 2.2 ratios were maximally reduced on day 5 of MCMV infection and correlated strongly with peak virus recovery from spleen, bone marrow, and peripheral blood leukocytes. These results indicate that acute MCMV infection of mice causes abnormalities in T-lymphocyte subset ratios and responsiveness to mitogen similar to the abnormalities observed in human cytomegalovirus infections. MCMV infection of mice is a useful model to study the mechanism by which cytomegalovirus infections induce altered T-lymphocyte subpopulations.