Immunologic behavior of lymphocytes in experimental viral myocarditis: significance of T lymphocytes in the severity of myocarditis and silent myocarditis in BALB/c-nu/nu mice.

To clarify the immune mechanism in myocarditis, we examined by immunofluorescence techniques the serial changes in percentages of T and B lymphocytes in the heart, spleen, and peripheral blood of DBA/2 mice inoculated with encephalomyocarditis (EMC) virus (experiment I). B cells were demonstrated by staining with fluorescein isothiocyanate (FITC)-labeled rabbit antimouse immunoglobulin (Ig). T cells were demonstrated with rat anti-Thy1.2 monoclonal antibody plus FITC-labeled antimouse Ig. There was a marked decrease in T cells in peripheral blood and a moderate decrease in the cells in the spleen on day 14. There were no significant changes in B cells in peripheral blood or spleen throughout the entire period and T cells accounted for approximately 80% of the cells in the myocardium on days 7 and 14. To confirm the involvement of T cells in the development of myocarditis, we also carried out studies in which BALB/c-nu/nu mice (group 1, n = 58), BALB/c-nu/+ mice (group 2, n = 54), and BALB/c-nu/nu mice injected with 5 X 10(7) spleen cells from BALB/c-nu/+ mice (group 3, n = 50) were inoculated with EMC virus (experiment II). Four mice from each of the three groups were killed on day 6 for virologic studies. In experiment II, there were no significant differences in the incidence of myocarditis among the three groups. Virus titrations of the heart and serum neutralizing antibody titers did not show any significant differences between the three groups on days 6 and 16.(ABSTRACT TRUNCATED AT 250 WORDS)