STAT3 and neoplasm: In contrast, Bregs suppress anti-tumor immunity via IL-10 and TGF-β production, activating the JAK/STAT3 and Smad pathways to inhibit cytotoxic T cell and dendritic cell functions, while PD-L1+ B cells contribute to immune checkpoint-mediated resistance (Zhang et al., 2019b; Catalán et al., 2021; Li T. et al., 2023).