Fig. 5: CD28 expression on CD8⁺ T cells in the tumor microenvironment negatively correlates with CD73 expression.

a Mice were subcutaneously injected with B16.gp33 melanoma cells (2 × 10⁶ cells per mouse). Eight days later, tumor-draining lymph nodes were harvested. Total lymph node cells were subjected to flow cytometric analysis for CD73 expression on CD28⁻CD8⁺ (solid black) and CD28⁺CD8⁺ (solid red) T cells (n = 20, each). Lymph nodes harvested from tumor-free mice (controls) were subjected to flow cytometric analysis for CD73 expression on CD28⁻CD8⁺ (empty black) and CD28⁺CD8⁺ (empty red) T cells (n = 7, each). b As a, on day 20 after B16.gp33 implantation, tumors were dissected and dissociated into single cells. Single-cell suspensions were subjected to flow cytometric analysis for CD73 expression on CD28⁻CD8⁺ (black) and CD28⁺CD8⁺ (red) T cells (n = 4). Relative MFI of CD73 on CD28⁻CD8⁺ and CD28⁺CD8⁺T cells was compared against isotype control. c CD73 expressions on CD28⁻CD8⁺ (n = 30, black) and CD28⁺CD8⁺ (n = 30, red) CD8⁺ T cells in TILs was compared to their respective counterparts in PBMC (TIL/PBMC) of colon cancer. d CD73 expressions on CD28⁻CD8⁺ and CD28⁺CD8⁺ CD8⁺ T cells in TILs were compared to their respective counterparts in PBMC from the same individual. CD73 MFI from TILs and PBMC was analyzed by paired student t-test (n = 30). Statistical evaluations were performed using the Student’s t-test with data expressed as the mean ± standard error of the mean (a–d). *p < 0.05, **p < 0.01, ***p < 0.001; ns, not statistically significant.