〔Abstract〕 To construct CSF1R + / - mice and to analyze their genotypes , so as to provide animal model basis for disease pathological mechanism and drug target. Methods A linearized targeting vector was designed ac- cording to Cre/Loxp system . A Loxp site was inserted upstream of the 5th exon of the CSF1R gene , and a neomycin resistance box with Loxp sites on both sides was inserted downstream of the 5th exon . The linearized targeting vector was electroporated into embryonic stem cells . The correctly targeted embryonic stem cells were injected into the blastocysts of C57BL/6J mice to obtain chimeric mice , which were bred with Zp3-Cre mice . The newborn mice were numbered 9 - 14 days after birth and their tails were cut. The DNA of the mice was extracted , and the geno- type of the mice was identified by polymerase chain reaction and agarose gel electrophoresis . The expression of CSF1R in mouse macrophages was detected by flow cytometry . The expression of CSF1R in mouse tissues was de- tected by Western blot. Results The results of agarose gel electrophoresis showed that 453 bp bands were ampli- fied in wild type mice , and 453 bp and 650 bp bands were amplified in heterozygous mice . The results of flow cy- tometry showed that the expression of CSF1R in peritoneal macrophages and bone marrow-derived macrophages of CSF1R heterozygous mice was lower than that of WT group ( P < 0. 05) . The results of Western blot showed that the expression of CSF1R in spleen , kidney and brain tissue of CSF1R heterozygous group was lower than that of WT group (P < 0. 05) . Conclusion CSF1R + / - mice are successfully constructed , reproduced and identified , which provides an animal model basis for further revealing the potential mechanism of CSF1R in immune regulation .