〔Abstract〕 To explore the breeding and genotyping of CCR2 knockout mice , and to verify the applica- bility of the polymerase chain reaction (PCR) method for genotype detection of CCR2 knockout mice . Methods The introduced CCR2 pure male mice and wild-type female mice were mated and bred to produce the offspring gen- eration , the obtained F1 generation heterozygous mice were continued to be mated . DNA was extracted by clipping the tail tissues of the mice at the age of 2 weeks , the target gene fragment was amplified by PCR , and the genotypic results were determined by agarose gel electrophoresis . The proportion of purebred progeny carrying the CCR2 knockout gene was increased by genetic crosses , the effect of CCR2 knockout in the progeny mice was verified by using Western blot against major immune cells and key organs , and flow cytometry was used to detect whether the knockout of the CCR2 gene had any effect on the function of the immune system by targeting the major immune cells . Results CCR2 knockout mice were successfully bred and characterized , and three genotypes of F2 genera- tion mice were obtained : CCR2 + / + , CCR2 + / - , and CCR2 - / - . The offspring genotypes were identified by PCR , and Western blot showed extremely low CCR2 protein expression in CCR2 knockout mice . Flow analysis showed that CCR2 knockdown reduced the expression of CD4 + T and Th1 cells in mouse spleen-derived T cells , but did not affect macrophage function . Conclusion Correct breeding and identification are important ways to get the pure CCR2 knockout mice , and PCR method for identifying mouse genotypes is simple , fast and reliable .