The effects of biological response modifiers (BRMs) on the functions of two types of dendritic cells (DCs) were examined in relation to anti-tumor therapy. The two BRMs studied in our assay system were OK432 (a streptococcal preparation) and KP-40 (Propionibacterium avidum: a heat-inactivated bacterial vaccine). Recently, techniques for isolating human DCs from peripheral blood have been established, and DCs can be divided into two subsets: CD11c+ DCs (myeloid DC population) and CD11c- DCs (lymphoid DC population). Both OK432 and KP-40 were found to up-regulate the activity of myeloid-lineage DCs: the expression of major histocompatibility complex (MHC) class II molecules and adhesion/costimulatory molecules increased, and the production of IL-12 also increased. Therefore, DCs pulsed with OK432 and KP-40 could be applied to vaccination as a new adjuvant for specific immunotherapies.