Fig. 4

Tumor-derived exosomes from multiple cell lines are responsible for the induction of suppressor CD8⁺ T cells. CD8⁺ T cells were purified from human buffy coat and then incubated for 6 h with either TDEs from Tu167, head and neck cancer (HN60), squamous cell carcinoma (SCC0209) cells lines, or membrane-vesicle free complete RPMI (negative control). After incubation cells were washed and grown in exosome-free complete RPMI. On day 6, a portion of CD8⁺ T cells were removed and used for the above suppression assay at a 2:1, Responder T cells: CD8⁺ T cells. A BrdU incorporation ELISA suppression assay was done for 72 h with BrdU being added 22 h before the end of the experiment. Data represents the mean +/− SD of 3. To compare means, a one-way analysis of variance was used with a Bonferroni multiple comparison test. **p < 0.01, and ***p < 0.001 for the indicated groups vs. responder T cells (Tresps) alone