Figure 4. Activation of CD4⁺ T_EM cells at site of tumor challenge.

Thy1.1⁺/CD62L^low/CD4⁺ T cells prepared from MCA 205 tumor-draining LN, activated in vitro then adoptively transferred into tumor-free Thy1.2 hosts. Day 273 later mice were challenged by i.v. injection of MCA 205 tumor cells. Lungs and spleen were harvested at the indicated time points post tumor challenge. Histograms are gated on Thy1.1⁺/CD4⁺ double positive cells. Open histograms indicate isotype control. On days 0 and 32 when CD4⁺ T cells were in a resting state, CD62L was expressed on approximately 50% of splenic T cells but not on lung-resident T cells. On days 3 and 7 following tumor challenge, CD69 expression was up-regulated, and CD127 expression was down-regulated on lung cells. The data are representative of two independently performed experiments.