Cloning of a novel interleukin (IL)-20-like gene in rainbow trout Oncorhynchus mykiss gives an insight into the evolution of the IL-10 family

A high level of IL-20L expression in immune related tissues and in the brain, suggests an important role of the fish IL-20L molecule in both the fish immune system and nervous system. Although the exact cell types expressing IL-20L have yet to be defined, macrophages express IL-20L. Moreover, the IL-20L expression in the macrophage cell line RTS-11 was modulated by pro-inflammatory cytokines, signalling pathway activators, microbial mimics and the immuno-suppressor dexamethasone. These data suggest that trout IL-20L is an important player in the cytokine network. The increased expression of IL-20L was only detected at late stages (4-24 h) of LPS stimulation in RTS-11 cells and in spleen 24-72 h after infection with Yersinia ruckeri, and suggests that the increased expression of IL-20L by LPS and infection may be via the rapid increase of pro-inflammatory cytokines (e.g., IL-1β) and other factors that is known to occur.