Since mice lack a homologous gene to human CD89, introducing the human CD89 gene into mice aids in studying immune mechanisms and IgA nephropathy (IgAN). The Cd11b-hCD89 (FCAR) mouse is a humanized model constructed by integrating the coding sequence (CDS) of the human CD89 gene downstream of the stop codon in the mouse Cd11b (Itgam) gene. The human CD89 gene, regulated by the mouse Cd11b gene promoter, is specifically expressed in myeloid cells. Cd11b-hCD89 (FCAR) mice successfully express the human FCAR gene, with the human FCAR protein detectable in peritoneal myeloid cells. Therefore, Cd11b-hCD89 (FCAR) mice can be used to study immune responses, autoimmune mechanisms, tumors, and infectious diseases.