Figure 3. Tumor challenge induces rapid proliferation of long-term memory cells.

Thy1.1⁺/CD62L^low/CD4⁺ T cells were prepared from MCA 205 or MCA 207 tumor-draining LNs, activated in vitro for 29 days then adoptively transferred into tumor-free Thy1.2 hosts. (A) Day 273 for MCA 205 tumor model, or (B) day 277 for MCA 207 tumor model, the mice received tumor challenge by i.v injection. Lung, spleen and blood were harvested from two animals and pooled for processing. The number of Thy1.1⁺/TCRβ⁺ double T cells was enumerated. Similar results were obtained with Thy1.1/CD4 double staining. The Th1.1⁺ memory cells in the lung dramatically increased to the maximum at day 7 post tumor challenge, and peaking in the spleen at day 18.