However, Flagellin B (FlaB) failed to attract and activate enough NK, CD4, CD8, and NKT cells in tumour tissue; therefore, Zhang Y et al. designed a synergistic cancer immunotherapy system that utilises programmed S. typhimurium to secrete heterologous FlaB conjugated to interleukin-15 proteins to compensate for this deficiency (Zhang et al., 2023). This evidence concerns the gene CD4 and cancer.