In vivo effect of anti-CD69 treatment in the absence of tumor challenge. The splenocytes of mice treated in vivo with mAb CD69.2.2 or control isotype mAb were examined ex vivo. Twenty-four hours after mAb injection (200 μg intravenously), cytotoxicity of splenocytes against RMA-S, RM-1, and YAC-1 target cells was assessed. The findings represent 2 experiments conducted independently. ▪ indicates the splenocytes of mice treated with mAb CD69.2.2, and □, the control mice (n = 4; mean ± SD).