Diverging In Vitro Antibody Isotype Switching Preference in B-Lymphocytes from C57BL/6 and FVB Mice

Inbred strains of laboratory mice are commonly used in different immunological studies, with varying results. However, these variations are often overlooked and the underlying molecular mechanisms are less explored. In this study, we analyzed the differences in B-lymphocyte response and mechanisms of class switch recombination in two commonly used mouse strains, FVB and C57BL/6. These two strains of mice differ in their major histocompatibility complex (MHC) antigens, C57BL/6 having H-2b and FVB having H-2q, along with multiple cryptic changes. Analysis of in vitro class switch recombination showed that lymphocytes from these two strains of mice had altered preference for immunoglobulin isotype switching, with C57BL/6 producing more IgG1 and IgG3, but less IgG2b compared to FVB. Furthermore, cell-cycle patterns and gene expression studies for critical genes showed moderate differences between the two strains, suggesting that the cells opted for different molecular mechanisms under identical culture conditions.