https://www.sciencedirect.com/science/article/pii/S0144861721014600
The team of Huazhong Agricultural University analyzed the cellular and molecular mechanism of chito-oligosaccharides enhancing humoral immunity of fish
In order to explore the activation of fish B cells and the mechanism of antibody production, Zhang Yongan's team first prepared IgM heavy chain monoclonal antibodies of grass carp, and found that there were two types of IgM+ B cell subsets in healthy grass carp, namely IgM+ B lymphocytes and IgM+ myeloid cells. Among them, IgM+ myeloid cells were further identified as mammalian plasma cells, and recombinant expression of CD40L and IL-21 could synergically promote IgM+ plasma cell generation and IgM secretion, indicating that fish B cells could be significantly induced to differentiate by related signaling molecules. Based on this, it was further found that chito-oligosaccharides could bind to the mannose receptor (MR) and Integrin on the surface of B cells to activate the downstream signaling pathway, and finally strongly induce the proliferation and differentiation of grass carp spleen IgM+ B lymphocytes into IgMlo and IgMhi B cell subsets. Among them, IgMlo B cells were proved to be a kind of plasma blast cells with low expression of IgM on the membrane surface and able to secrete natural IgM. In vivo experiments further confirmed that IgMlo plasmocytes induced by chitosaccharide can migrate from the spleen to the blood and secrete a large amount of natural IgM capable of targeting pathogen-associated molecular patterns (PAMP), thereby improving disease resistance in fish. This study revealed for the first time the cellular and molecular mechanism of chito-oligosaccharide enhancing humoral immunity of fish, which provided a strong theoretical support for the application of chito-oligosaccharide in fish culture. In addition, the study further clarified the innate immune properties of fish B cells and provided a good model for studying the differentiation of fish B cells.