Autologous tumor cells plus IL-12–secreting bystander cells induced CD4⁺ T cells to proliferate upon in vitro stimulation with syngeneic tumor.

After 4 immunizations splenocytes from the indicated experimental groups were collected and purified CD4⁺ T cells were incubated for 5 days in the absence (■) or presence (▪) of irradiated A20 cells. [³H] incorporation is given as counts per minute (cpm) minus values for medium alone. Incorporation of irradiated A20 cells alone was comparable to that in medium. Data are represented as means (+ SDs) of the T-cell cpm per well from 3 mice in each group, analyzed individually.