During an inflammatory response, zebrafish tnfa and tnfb are expressed by different cell types and have distinct expression kinetics

Abstract

Tumour necrosis factor (TNF, TNFSF2) is a central regulator of inflammation. While mammalian TNF biology is well understood, its pleiotropic role in other vertebrates remains unclear. Zebrafish (Danio rerio) possess two TNF homologues, tnfa and tnfb. Previous studies have focused mainly on tnfa, leaving tnfb largely unexplored. We generated two transgenic reporter lines, Tg(-3.2tnfb:eGFP-F)ump21Tg and Tg(-6.2tnfb:mCherry-F)ump22Tg, to track tnfb expression. Combining these reporter lines with high-resolution in vivo microscopy, other reporter lines, and public scRNAseq datasets, we define, in a cell type-specific manner, tnfb expression kinetics compared to those of tnfa and il1b. We found constitutive tnfb expression in neuromast mantle cells from 32 hpf, and inducible expression in macrophage and neutrophil subsets following caudal fin fold amputation or E. coli injection. After wounding, tnfb expression appeared first in macrophages, followed by neutrophils, with sequential tnfb, tnfa, and il1b expression in macrophages. These findings reveal distinct tnfb dynamics compared to tnfa, suggesting differential roles of these two cytokines, and establishing zebrafish as a model to study the pleiotropic functions of Tnf in vertebrates.