CD4 and neoplasm: Additionally, CD4+ T cell infiltration was markedly enhanced in the metastatic tumor microenvironment (Fig. 7e; Additional file 1: Fig. S28b), and a dramatic increase in CD8+ T cells was observed in the “HAQ/223Ra@HNPs + anti-PD-L1” group (Fig. 7e; Additional file 1: Fig. S28c), indicating a robust cytotoxic T cell response.