This strain is a mouse IgG1-C-terminal humanized model. The 2-4 exon encoding hinge region, CH2 domain, and CH3 domain in the mouse Ighg1 gene were replaced with corresponding human gene sequences. Human IGHG1 expression can be detected in the spleen and serum, making this model useful for research on the mechanism of immunoglobulin, IgG antibody development and screening, as well as tumor proliferation, migration, and chemotherapy resistance.