CD4 and cancer: In preclinical models, Chen Y et al. created an ultrasound-responsive bacterium to regulate IFN-γ release at the tumour site, promoting cancer cell apoptosis, macrophage polarisation from the M2 phenotype to the M1 phenotype, and CD4 + and CD8 + T-cell activation, all of which enhance the antitumour immune response (Chen et al., 2022).