Anaphylatoxins, which are involved in both pro-inflammatory processes and a variety of anti-inflammatory effects, are produced during granulocyte and monocyte adsorptive apheresis. We noticed the anti-inflammatory effects of C5a, the strongest anaphylatoxin, in granulocyte and monocyte adsorptive apheresis. The aim of this study was to investigate the effect of C5a on interleukin-1 receptor antagonist (IL-1ra) and hepatocyte growth factor (HGF) generation in granulocyte and monocyte adsorption. Peripheral blood containing nafamostat mesilate as an endogenous complement activation inhibitor was divided into four groups: (1) no recombinant C5a added, no contact with cellulose acetate (CA) beads (control group); (2) no C5a added, contact with CA beads; (3) C5a added, no contact with CA beads; and (4) C5a added, contact with CA beads. After incubation, IL-1ra and HGF in plasma were measured. IL-1ra was significantly higher in group 3, in which only C5a was added in the absence of CA beads, compared to groups 2 (P < 0.01) and 4 (P < 0.05). HGF was significantly higher only in group 4, in which C5a was added in the presence of CA beads (P < 0.05), but did not increase in the absence of CA beads. C5a can directly induce IL-1ra generation without the granulocyte and monocyte adsorption stimuli to CA beads, but can synergistically induce HGF generation with the adsorption stimuli, indicating C5a has different effects on IL-1ra and HGF generation.