CD4 EXPRESSION IS IMPORTANT BUT NOT ESSENTIAL FOR INFECTION WITH EXOGENOUS MOUSE MAMMARY-TUMOR VIRUS

We studied local events in the popliteal lymph nodes of CD4-deficient mice following foot pad injection with an MMTV strain which carries th e gene for a V beta 14-specific superantigen. Injection of the V beta 14-specific MMTV induced vigorous expansion of V beta 14(+) CD4(+) T c ells and B cells in their lymph nodes of CD4+/- heterozygous control m ice. On the other hand, CD4-/- mice injected with the MMTV showed a pr oliferation of V beta 14(+) T cells among the population of TCR alpha beta(+) CD4(-)CD8(-) T cells, although to a lesser extent. This phenom enon was not accompanied by vigorous B cell expansion. A PCR assay rev elated that the MMTV definitely infected the lymph nodes cells of the CD4-/- mouse. However, the infectivity of the MMTV in CD4-/- mice was approximately 20 rimes lower than that in CD4+/- mice. These findings indicate that, in MMTV infection of CD4-deficient mice, the superantig en-reactive T cells among the population of TCR alpha beta(+) CD4(-)CD 8(-) T cells substitute for the superantigen-reactive CD4(+) T cells o f normal mice, and that the absence of CD4 molecules decreased the inf ectivity of MMTV because of insufficient expansion of the superantigen -reactive T cells.