Evidence for the conservation of an immunoreactive monokine network in invertebrates

Mytilus edulis, a marine bivalve mollusc, contains hemocytes that share certain properties with cells of the human monocyte-macrophage lineage. Because of this and previously reported similar responses to opioids between Mytilus hemocytes and human granulocytes, we determined whether Mytilus might also possess monokines or an immune monokine-like network. We chose to study two monokines, interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF). We found that Mytilus hemocytes respond to recombinant human IL-1 and TNF in a fashion similar to human granulocytes. Furthermore, we show that as in the human system, it appears that IL-1 mediates at least part of its effects through immunoreactive (ir) TNF in Mytilus. Finally, we show that Mytilus hemolymph contains ir IL-1 and TNF. To our knowledge, this is the first demonstration of these substances in this system.