Cell-mediated cytotoxicity against murine cells infected with 6/94 virus, a parainfluenza type 1 isolate from multiple sclerosis brain tissue.

Maximum cytotoxicity to parainfluenza type 1 viral determinants occurs on day 5 post-immunization in mice with and without preexisting anti-6/94 virus antibody. Animals with preexisting anti-6/94 serum antibody, however, exhibited a markedly higher cytotoxic response. Syngeneic, allogeneic, and xenogeneic virus-infected cells induce virus-specific cytotoxicity, but only infected cells histocompatible with the effector cells can serve as susceptible target cells. The effector cell is a T cell, and hence cytotoxicity is thymus dependent. Coincident with the maximum cytotoxic activity on day 5 is the occurrence of pathological lesions, the sites of which are dependent on the route of inoculation.