%0 Journal Article %A McLain, L. %A Morgan, D. J. %A Dimmock, N. J. %T Protection of mice from lethal influenza by defective interfering virus: T cell responses %D 1992 %J Journal of General Virology, %V 73 %N 2 %P 375-381 %@ 1465-2099 %R https://doi.org/10.1099/0022-1317-73-2-375 %I Microbiology Society, %X The immune-mediated lethal influenza in C3H/He-mg (H-2k) mice infected with A/WSN influenza virus (H1N1) was investigated. A primary class I major histocompatibility complex-restricted, CD8+ cytotoxic T lymphocyte (CTL) response was found in the lungs with a peak activity at 5 days post-infection. Monoclonal antibody depletion in vivo showed that a lethal CD8+ cell response as well as a lethal CD4+ response was generated during infection. Mice survived infection only if both CD8+ and CD4+ cells were depleted. Mice infected with the same dose of virus, but treated with defective interfering (DI) A/WSN virus develop only a transient sub-lethal respiratory disease even though multiplication of virus in the lungs is undiminished, and we have shown here that this correlates with a reduction in the local CTL response. The mechanism by which DI virus beneficially modulates the immune response is discussed; it is proposed that there is classical, but cell type-specific DI virus interference in lymphocytes but not in the cells of the lung in which virus multiplies productively. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-73-2-375