CD4 and neoplasm: Notably, an obvious decrease in the proportion of regulatory T cells (CD3+CD4+Foxp3+, Tregs) was also seen in the PEG‐CuP‐COF@∆St + US group, demonstrating that PEG‐CuP‐COF@∆St + US‐mediated pyroptosis effectively reduced immunosuppression and remodeled tumor microenvironment (Figure 6C; Figure S22G, Supporting Information).