Mouse malignant T-lymphoma CS-21 cells grow in vitro in the presence of CA-12 lymph node stromal cells, but they undergo apoptotic cell death when separated from CA-12 stromal cells. In the course of examining the nursing effects of CA-12 stromal cells, we found that these cells provided some soluble factors that suppressed CS-21 cell apoptosis. We recently found that cysteine was an antiapoptotic soluble factor. In this report, we identify interleukin-7 (IL-7) as another antiapoptotic soluble factor secreted by CA-12 stromal cells. Although the activity of CPP32-like protease was increased in induction of CS-21 cell apoptosis, the addition of IL-7 suppressed the activity. The expression of Bcl-2 protein was down-regulated when CS-21 cells were cultured alone, but the addition of IL-7 recovered the expression of Bcl-2. These results indicate that CA-12 stromal cells inhibit CS-21 cell apoptosis by producing IL-7, which leads to the suppression of CPP32-like protease activation and the expression of Bcl-2 protein.