Figure 6.

Antigen-specific effector CD4⁺ T cells can control lung metastasis while memory CD4⁺ T cells prevent mice from lung metastasis. (A, B) Image of lung samples of metastatic tumor models in which mice were inoculated with 5×10⁵ B16-GP cells intravenously and 8 Days later transferred with 1×10⁶ effector CD4⁺ T cells isolated from LCMV-Armstrong-infected mice. Tumor bearing mice were sacrificed on Day 15 (A) or Day 20 (B) after B16-GP inoculation. (n=4/group on Day 15, n=6/group on Day 20). Before Day 15, a mouse died and three mice died before Day 20. The statistical analyses of the metastatic foci are shown beside. (C, D) Image of lung samples of metastatic tumor models in which naïve mice were transferred with 1×10⁵ memory CD4⁺ T cells or PBS and then challenged with 5×10⁵ B16-GP. Mice were sacrificed on Day 11 (C) and Day 15 (D) post tumor challenge. On Day 11, n=4 in PBS group, n=3 in memory CD4 group, on Day 15, n=4/group. The statistical analyses of the metastatic foci are shown beside. (E) CD4⁺CD25^-GITR^- T cells were separated from the lung tissue and the draining lymph nodes of B16-GP tumor-bearing mice eight days after tumor inoculation and 1.5×10⁶ PD-1⁺ CD44⁺CD25^-CD4⁺T cells (tumor-reactive) or PBS were transferred into recipient mice (n=4/group) challenged with B16-GP four days before. The tumor-bearing recipient mice were sacrificed on Day 15 post tumor inoculation and the image of lung samples harvested from the mice and the statistical analysis of the metastatic foci is shown. Statistical differences are calculated by unpaired t test. *p < 0.05, **p < 0.01, ****p < 0.0001. Data are presented as mean ± SEM.