THE CYTOTOXIC T-LYMPHOCYTE RESPONSE TO SENDAI VIRUS IS UNIMPAIRED IN THE ABSENCE OF GAMMA-INTERFERON

Sendai virus is eliminated from the respiratory tract of gamma interfe ron (IFN-gamma) -/- BALB/c mice with normal kinetics. The level of vir us-specific cytotoxic t-lymphocyte (CTL) activity in the cell populati on recovered by bronchoalveolar lavage is unimpaired, the prevalence o f interleukin-4 (IL-4)-producing cells is increased, and the titers of virus-specific immunoglobulins IgG1 and IgG2b are higher in the IFN-g amma -/- mice. The emergence of this T-helper 2 response profile in bo th lymphoid tissue and the pneumonic lung has no obvious deleterious c onsequences, Virus clearance is slightly delayed following depletion o f the CD4(+) subset, with the effect being similar in magnitude for IF N-gamma -/- and +/+ mice. However, the generation of CTL precursors (C TLp) is diminished in the IFN-gamma -/- (but not +/+) mice in the abse nce of concurrent CD4(+) T help. Apparently the clonal expansion of th e CTLp population can be promoted either by a cytokine (perhaps IL-2) produced by the IFN-gamma -/- CD4(+) T cells or by IFN-gamma made by o ther cell types in the +/+ mice.