Abstract

B lymphocyte-induced maturation protein 1 (Blimp-1), a transcription factor containing zinc finger , is required and sufficient to trigger terminal differentiation of B cells in mammals. The Blimp-1 ( OnBlimp-1 ) from Nile tilapia ( Oreochromis niloticus ) was identified and characterized its expression pattern during B cell activation and maturation. The cDNA of OnBlimp-1 open reading frame is 2547 bp encoding a protein of 848 amino acids and the predicted molecular weight is 93.36 kDa. OnBlimp-1 contains a SET domain and five ZnF_C2H2 domains, which shares high homology with that of other species. OnBlimp-1 transcription was detected in all examined tissues with high expression in the spleen (SPL). Analysis of sorted lymphocyte populations , including IgM + and IgM − cells from peripheral blood (PBL), SPL and anterior kidney (AK), indicated that the OnBlimp-1 transcription was highly expressed in the IgM + B cells. Upon LPS stimulation, OnBlimp-1 expression was up-regulated in tissues of PBL, SPL and AK significantly. The expression of OnBlimp-1 , as well as the secreted IgM , was significantly up-regulated in the SPL and AK leukocytes stimulated with anti-OnIgM monoclonal antibody and LPS in vitro , respectively. Above results suggest that OnBlimp-1, a cytokine regulating the terminal differentiation of activated B cells to antibody-secreting cells, is likely to play important roles in B cell activation and maturation in Nile tilapia.