Loss of proliferative potential and anti-tumor cytotoxicity in CTLs is reversible.

<p><b>A</b>. The loss of proliferation potential of CD3 mAb-stimulated CTLs is reversible. The tumor-specific CTLs were re-stimulated with CD3 mAb for 2 times, followed by re-stimulation with tumor cells. Proliferation was measured by analyzing ³H-thymidine incorporation 2 days after the second tumor cell re-stimulation. <i>Column</i>, mean; <i>bar</i>, SD. <b>B</b>. The decreased anti-tumor cytotoxicity of CD3 mAb-stimulated CTLs can be enhanced by antigen re-stimulation. CTLs were stimulated with tumor cells (Pre-tumor cell) or CD3 mAb (pre-CD3 mAb) every 7 days for 2 rounds, followed by re-stimulation with tumor cells twice more rounds before adoptive transfer. Shown are photomicrographs of individual lungs of mice. The number of tumor nodules was quantified and shown in the bottom panel. Each dot represents total tumor nodule counts from a single mouse.