Vertebrate cytokines interleukin 12 and gamma interferon, but not interleukin 10, enhance phagocytosis in the annelid Eisenia hortensis

Phagocytosis assays employing class I [interleukin 12 (IL-12)], and class II [gamma interferon (gIFN) and IL-10] human recombinant cytokines were carried out to determine the biological effects of these molecules on innate immune responses in the earthworm Eisenia hortensis. Coelomocytes from E. hortensis were pre-incubated with the cytokines for 16-20 h in vitro followed by introduction of Escherichia coli expressing green fluorescent protein (E. coli/GFP). The pro-inflammatory cytokines IL-12 and gIFN stimulated statistically significant (p ⩽ 0.05) enhanced phagocytosis of E. coli/GFP by hyaline amoebocytes as determined by flow cytometry; 10 out of 21 earthworms (48%) responded to IL-12, while eight out of 21 (38%) responded to gIFN. In contrast, the anti-inflammatory cytokine IL-10 neither stimulated nor inhibited phagocytosis in nine earthworms tested. These results demonstrate that vertebrate pro-inflammatory cytokines influence invertebrate cellular responses of immune cells causing enhanced phagocytic activity in earthworm coelomocytes.