Vertebrate interleukins originated in invertebrates?

Previous studies have demonstrated that invertebrate immune and neural tissues contain mammalian-like cytokines, which activate specific cellular functions. Therefore, it was of interest to attempt to identify these molecules via Applied Biosystems Human Genome Survey Arrays. The array was used to analyze the transcriptional profiles of Mytilus edulis RNA samples. The Applied Biosystems Human Genome Survey Array contains 31,700 60-mer oligonucleotides probes representing a set of 27, 868 individual human genes and more than 1,000 control probes. We show interleukin-like and tumor necrosis factor-like genes among other cytokine-like genes significantly expressed in this invertebrate tissue with a signal to noise value greater than 2. In morphine treated tissue additional cytokine genes were expressed. These cytokine-like genes are directly related to previously discovered molecules in invertebrates, suggesting that they first appeared earlier in evolution.