Delicaflavone reactivates anti-tumor immune responses by abrogating monocytic myeloid cell-mediated immunosuppression

•Immune responses contribute to the anti-tumor effect of total biflavonoids extract from Selaginella doederleinii (TBESD).•TBESD restrains the viability and immunosuppressive properties of M2-TAMs and M-MDSCs, and re-educates M2-TAMs to an M1 like phenotype.•TBESD blocked Jak1/STAT6 signaling pathway in M2-TAMs and MDSCs.•Delicaflavone, a monomer isolated from TBESD, mediates the anti-tumor immune effect of TBESD both ex vivo and in vivo.