Investigating the importance of B cells and antibodies during Trichuris muris infection using the IgMi mouse

The IgMi mouse has normal B cell development; its B cells express an IgM B cell receptor but cannot class switch or secrete antibody. Thus, the IgMi mouse offers a model system by which to dissect out antibody dependent and antibody independent B cell function. Here, we provide the first detailed characterisation of the IgMi mouse post-Trichuris muris (T. muris) infection, describing expulsion phenotype, cytokine production, gut pathology and changes in T regulatory cells, T follicular helper cells and germinal centre B cells, in addition to RNA sequencing (RNA seq) analyses of wild type littermates (WT) and mutant B cells post infection. IgMi mice were susceptible to a high dose infection; with reduced Th2 cytokines and elevated B cell-derived IL-10 in mesenteric lymph nodes (MLN) compared to controls. A low dose infection regime revealed IgMi mice to have significantly more apoptotic cells in the gut compared to WT mice, but no change in intestinal inflammation. IL-10 levels were again elevated. Collectively, this study showcases the potential of the IgMi mouse as a tool for understanding B cell biology and suggests that the B cell plays both antibody dependent and independent roles post high and low dose T. muris infection.