The Ancient Cytokine BAFF- and APRIL-like Molecule Regulates the Functionality of Teleost IgM+ B Cells Similarly to BAFF and APRIL

Abstract TNF superfamily (TNFSF) members, such as BAFF and a proliferation-inducing ligand (APRIL), emerged in vertebrates key regulators of B cell homeostasis activation. Many cartilaginous teleost fish contain an additional gene, designated BAFF- APRIL-like molecule (BALM), unknown function lost tetrapods. In this study, we have performed wide characterization the functions BALM on naive cells for first time, to our knowledge, teleosts using rainbow trout (Oncorhynchus mykiss) model. Similar APRIL, increased survival promoted proliferation peripheral blood IgM+ cooperated with BCR cross-linking increase rate cells. also seemed be differentiating factor cells, it IgM secretion size. Additionally, appeared Ag-presenting properties augmenting MHC class II surface expression upregulating phagocytic capacity these Finally, fact that there was no synergy between BAFF/APRIL any strongly suggests signals through same receptors APRIL carry out its functions. This hypothesis further supported competitive binding assays. The results presented provide relevant information understanding how TNFSF members cooperate regulate functionality, helping us interpret evolutionary relations molecules family.