Antimicrobial Protein LECT2-b Helps Maintain Gut Microbiota Homeostasis via Selectively Targeting Certain Pathogenic Bacteria.

Antimicrobial peptides/proteins (AMPs) constitute a critical component of gut immunity in animals, protecting the gut from pathogenic bacteria. However, the interactions between AMPs and gut microbiota remain elusive. In this study, we show that leukocyte-derived chemotaxin-2 (LECT2)-b, a recently discovered AMP, helps maintain gut homeostasis in grass carp (Ctenopharyngodon idella), one of the major farmed fish species globally, by directly regulating the gut microbiota.

An Atlas of Grass Carp IgM+ B Cells in Homeostasis and Bacterial Infection Helps to Reveal the Unique Heterogeneity of B Cells in Early Vertebrates.

Teleost B cells are primitive lymphocytes with both innate and adaptive immune functions. However, the heterogeneity and differentiation trajectory of teleost B cells remain largely unknown. In this study, the landscape of grass carp IgM+ (gcIgM+) B cells was revealed by single-cell RNA sequencing.

Molecular and Functional Analyses of the Primordial Costimulatory Molecule CD80/86 and Its Receptors CD28 and CD152 (CTLA-4) in a Teleost Fish.

The moderate activation of T cells in mammals requires the costimulatory molecules, CD80 and CD86, on antigen-presenting cells to interact with their respective T cell receptors, CD28 and CD152 (CTLA-4), to promote costimulatory signals. In contrast, teleost fish (except salmonids) only possess CD80/86 as their sole primordial costimulatory molecule. However, the mechanism, which underlies the interaction between CD80/86 and its receptors CD28 and CD152 still requires elucidation.

Chromosome-level genome assembly of grass carp (Ctenopharyngodon idella) provides insights into its genome evolution.

Background: The grass carp has great economic value and occupies an important evolutionary position. Genomic information regarding this species could help better understand its rapid growth rate as well as its unique body plan and environmental adaptation.

Results: We assembled the chromosome-level grass carp genome using the PacBio sequencing and chromosome structure capture technique.

Complement C3a Enhances the Phagocytic Activity of B Cells Through C3aR in a Fish.

The complement system is an important part of the immune system of teleost fish. Besides, teleost B cells possess both phagocytic activity and adaptive humoral immune function, unlike mammalian B1 cells with phagocytic activity and B2 cells specific to adaptive humoral immunity. However, the cross talk between complement system and phagocytic B cells in teleost fish still requires elucidation.

LECT2 Is a Novel Antibacterial Protein in Vertebrates.

In vertebrates, leukocyte-derived chemotaxin-2 (LECT2) is an important immunoregulator with conserved chemotactic and phagocytosis-stimulating activities to leukocytes during bacterial infection. However, whether LECT2 possesses direct antibacterial activity remains unknown. In this article, we show that, unlike tetrapods with a single gene, two genes exist in teleost fish, named and Using grass carp as a research model, we found that the expression pattern of grass carp () is more similar to that of in tetrapods, while has evolved to be highly expressed in mucosal immune organs, including the intestine and skin.

Plasmablasts induced by chitosan oligosaccharide secrete natural IgM to enhance the humoral immunity in grass carp.

Chitosan oligosaccharide (COS) is an attractive immunopotentiator capable of driving humoral immunity in vertebrates, but its cellular and molecular mechanisms still require elucidation. In this study, COS induced the proliferation and differentiation of splenic IgM B cells into IgM and IgM B cell subsets in grass carp (Ctenopharyngodon idella). The IgM B cells were further identified as short-lived plasmablasts that secreted natural IgM with binding-abilities to lipopolysaccharide (LPS) and peptidoglycan (PGN).

Membrane IgM plasma cells in grass carp (Ctenopharyngodon idella): Insights into the conserved evolution of IgM plasma cells in vertebrates.

Teleost fish are the most primitive bony vertebrates that contain B cells; thus, comparative analysis of teleost naïve/mature B cells and plasma cells can provide helpful evidence for understanding the evolution paradigms of these two B-cell subpopulations in vertebrates. In this study, we developed monoclonal antibody against grass carp IgM and identified two different IgM cell subsets: IgM lymphocytes (Lym), resembling naïve/mature B cells, and IgM myeloid cells (Mye), resembling plasma cells. Like plasma cells in mammals, the size of IgM Mye is significantly larger than that of IgM Lym, as revealed by flow cytometric analysis and transmission electron microscopy.