Cell-mediated immunity assayed by 51Cr release test in mice infected with mouse adenovirus

Immune spleen cells (ISC) from mice immunized with a sublethal dose of mouse adenovirus (M-Ad) were shown by the 51Cr release test to be cytotoxic to target mouse embryonic cells or lymphoid cells infected with M-Ad. The number of ISC required for release of statistically significant amounts of 51Cr from target cells varied from one sample to another, ranging from 5 to greater than or equal to 30 ISC per target cell. When 24-h-infected mouse embryonic cells were used as targets, the release of 51Cr became evident in 6 h after the addition of ISC to the cells, gradually increased with time, and then leveled off. Cytolytic activity of M-Ad ISC is specific for M-Ad, since ISC do not lyse mouse embryonic cells infected with human adenovirus type 12 and vice versa. Kinetic study of the development of cell-mediated immunity to M-Ad assayed by 51Cr release showed that cytolytic activity of ISC in infected mice became detectable 4 days postinfection, reached its peak level about 7 to 10 days postinfection, and fell to undetectable levels about 10 days thereafter. This is consistent with the data obtained by inhibition of intracellular viral antigen synthesis or by the macrophage migration inhibition test in our prevous reports.