LAUSR

Abstract B lymphocyte stimulating factor (BLyS) belongs to the tumor necrosis family (TNF), which is a key cytokine in promoting the survival, proliferation, differentiation and apoptosis of B cells, and regulating the functions of T cells. However, functions of BLyS in teleosts are not well known. In the present study, the functions of BLyS in golden pompano (Trachinotus ovatus) (TroBLyS) were conducted through in vivo and in vitro experiments. Gene expression analysis suggested that TroBLyS was ubiquitously expressed in different tissues. Particularly, TroBLyS was most expressed in head kidney, followed by spleen, and liver. After Vibrio harveyi stimulation, the expressions of TroBLyS in head kidney, spleen, and liver were significantly upregulated. Recombinant TroBLyS (rTroBLyS) in vitro could promote lymphocytes proliferation and survival. Moreover, overexpression of TroBLyS in vivo in fish significantly promoted the activation of macrophages, increased the secretion of cytokines and chemokines, and reduced V. harveyi colonization in tissues. When the expression of TroBLyS was inhibited in T. ovatus, the bacterial count of V. harveyi was significantly increased than that in the control fish. Furthermore, the mortality of fish which was administrated of pTroBLyS for two weeks, was significantly reduced after V. harveyi infection, suggesting that TroBLyS had the potential as an immune enhancer. Our study indicated that TroBLyS might be involved in the antibacterial immune responses and has the potential as an immune system enhancer in T. ovatus.