Expressed quantitatively, a simultaneous introduction of costimulatory signals via CD28 (signal 2a) and IL-2 receptor (signal 2b) led to a 20–40% increased bystander antitumor activity in passage 1 (days 7–10) and passage 2 (days 10–13) when compared to a tumor vaccine with only one costimulatory signal (for more details, see [42]). The gene discussed is CD28; the disease is neoplasm.