CD4 and neoplasm: Another important finding of this study relates to the ability of a single intraperitoneal injection of attenuated Salmonella to induce a significant decrease in the percentage of CD4+ and CD8+ TILs that express the inhibitory immune checkpoint molecules PD-1 and LAG-3, suggesting its potential to reverse tumor immune tolerance and diminish T-cell exhaustion and, therefore, enhance T cell-mediated anti-tumor immunity.