The role of lymph node-derived stromal cells on growth and suppression of apoptosis of mouse malignant T-lymphoma cells

Using mouse malignant T-lymphoma CS-21 cells, we investigated the cell- cell interaction between lymphoma cells and lymph node stromal cells in vitro. CS-21 lymphoma cells continuously grew when the cells were cocultured with CA-12 lymph node stromal cells. However, when CS-21 cells were separated from the CA-12 stromal cells, they underwent apoptosis. Suppression of CS-21 cell apoptosis was achieved by adhesion to CA-12 stromal cells. To identify adhesion molecules, we established several clones of monoclonal antibodies that were able to partially inhibit adhesion of CS-21 lymphoma cells to a monolayer of CA-12 stromal cells. Treatment of CS-21 lymphoma cells with the monoclonal antibodies, which specifically bind to the cell adhesion molecules of 168 kDa and 23 kDa, suppressed the apoptosis of CS-21 lymphoma cells. We recently identified 168-kDa and 23-kDa proteins as CD 45 protein tyrosine phosphatase and Thy-1 glycoprotein, respectively. Furthermore, we found that the apoptosis-inhibitory signals, transmitted by ligation of anti-Thy-1 monoclonal antibody, were mediated to a bcl-2-independent mechanism. These results suggest that CD 45 protein tyrosine phosphatase and Thy-1 glycoprotein contribute not only to the cell-cell adhesion but also to the suppression of apoptosis of CS-21 lymphoma cells.