Lyn inhibited BCR signal pathway mediates B-cell anergy induced by avian leukosis virus subgroup J

Abstract

Background: Immune tolerance induced by retrovirus is a prerequisite for tumorigeness. We had reported that B-cell anergy was the main reason for immune tolerance induced by avian leukosis virus subgroup J (ALV-J). However, the molecular mechanism remains unclear. Results: Initially, we found that Lyn showed down-regulation in chick embryo fibroblasts (CEF) and up-regulation in B-cells infected by ALV-J. So, we speculated that tyrosine kinase Lyn plays a key role in B-cell anergy induced by ALV-J. Confocal laser scanning microscopy (CLSM) and co-immunoprecipitation (Co-IP) results demonstrated that ALV-J indirectly regulated the expression of Lyn. To further investigate the role and regulatory mechanism of Lyn in B-cell anergy induced by ALV-J, the expression levels of Lyn and Syk at different phosphorylation site, the Ca 2+ mobilization, and the expression levels of NF-κB p65 protein in vitro and vivo were detected in B-cells. The result showed that Ca 2+ mobilization was delayed and p65 expression level was decreased in B-cells after ALV-J infection. Consistently, the retrieve of Ca 2+ mobilization, expression levels of NF-κB p65 were found after RNA interference of Lyn. Subsequently, we demonstrated that the activation of phosphorylated Lyn protein at Tyr507 site played a critical role in B-cells anergy, which were verified by the fact of the significantly up-regulation of the expression levels of phosphorylated Syk protein at Tyr525/526 site when RNA interference for Lyn were performed in B-cells. Furthermore, immunohistochemical (IHC) staining results confirmed that the expression levels of Lyn phosphorylated protein at Tyr507 site in bursal cells were increased, while the expression levels of Syk phosphorylated protein at Tyr525/526 sites were decreased. Conclusions: These findings suggested that Lyn inhibited BCR signal pathway mediates B-cell anergy under ALV-J infection，which will provide a new insight for revealing the molecular mechanism of immune tolerance induced by ALV-J. Keywords: avian leukosis virus subgroup J , B-cell anergy, immune tolerance, Lyn, Syk