Objective To construct myeloid-specific Spi1 gene knockout mice and analyze their genotypes,so as to provide animal model basis for the study of pathological mechanism of diseases and drug targets.Methods Ac-cording to the principle of CRISPR/Cas9 technology and Cre/LoxP system,sgRNA and Donor vectors were de-signed and constructed.The transcript of Exon 2(Exon 2)was used as the knockout region,and Loxp elements were placed on both sides of Exon 2.Cas9 protein,sgRNA and Donor vector were mixed and microinjected into the fertilized eggs of C57BL/6J mice,the fertilized eggs were transplanted into the uterus of C57BL/6J pregnant female mice,and F0 generation was obtained after 19～20 days.Positive F0 mice were mated with C57BL/6J mice to ob-tain stable F1 Spi1flox/+mice.Spi1flox/+mice of F1 generation were selfed to obtain Spi1flox/flox mice.Spi1flox/flox mated with Lyz2-Cre+mice to obtain Spi1flox/+/Lyz2-Cre+mice,and then mated with Spi1flox/flox,the Spi1flox/flox/Lyz2-Cre+mice were myeloid-specific Spi1 gene knockout(KO)mice.Spi1flox/flox/Lyz2-cre-mice were used as wild-type(WT)mice.DNA of WT and KO mice was extracted,and the genotypes were identified by agarose gel electro-phoresis after PCR amplification.Western blot was used to detect the expression of spleen focus forming virus provi-ral integration oncogene,Spi-1/purine rich box-1(PU.1)in immune cells of WT and KO mice.Results The results of PCR identification showed that the genotype of mice with only 220 bp amplified by flox primer was Spi1flox/flox homozygote,and the genotype of mice with 700 bp amplified by Lyz2-Cre primer was Lyz2-Cre+.Western blot showed that compared with WT group,the protein PU.1 was not expressed in bone marrow-derived macropha-ges(BMDMs)and peritoneal macrophages(PM)in KO group(P<0.01).There was no significant difference of statistics in the expression level of PU.1 in T cells between KO mice and WT mice.The results of PCR and West-ern blot showed that myeloid-specific Spi1 KO mice were successfully constructed.Conclusion The myeloid-spe-cific Spi1 gene KO mice are successfully constructed and identified,which provides animal model basis for further revealing the potential mechanism of PU.1 inimmune regulation.

Objective To construct Csf1r-CreERT2 R26REYFP reporter gene mice and assess the efficacy of Csf1r-CreERT2-mediated enhancement of CSF1R in CD45+cells labeled with yellow fluorescein protein EYFP.Methods Csf1r-CreERT2 mice were crossbred with R26REYFP homozygous mice,and Csf1r-CreERT2R26REYFP mice were identified through PCR and Western Blot analyses.Flow cytometry was employed to evaluate CSF1R tag-efficiency in CD45+cells across different mouse tissues following tamoxifen induction.Results Csf1r-CreERT2 R26REYFP reporter gene mice were acquired.In addition,it was found that Csf1r-CreERT2-mediated EYFP could effectively mark CSF1R in various tissues of mice and CD45+cells in different locations.Compared to the R26REYF P group,the highest labeling efficiency was observed in the brain tissue(P＜0.001),the lowest in the thymus tissue(P＜0.05),and no sig-nificant difference was observed in the spleen tissue.Conclusion Adult Csf1r-CreERT2 mice and R26REYFP mice are effective ways to obtain Csf1r-CreERT2 R26REYFP induced conditional fluorescence mice.Csf1r-CreERT2 can mediate EYFP to effectively trace CSF1R in CD45+cells in different parts of mice.

Objective To breed and identify the T lymphocyte-conditional Spi1 knockout mice for the further in-vestgation of the specific role of Spi1-encoded protein PU.1.Methods The Lck-Cre mice were mated with Spi1flox/flox mice to obtain Lck-Cre×Spi1flox/flox mice(T lymphocyte-specific Spi1 knockout mice),and the genotype was determined by polymerase chain reaction(PCR)and agarose gel electrophoresis.Magnetic beads were used to sort out the splenic T lymphocytes,and the knockdown efficiency of PU.1 in T cells was detected by Western blot,quantitative real-time PCR(qPCR)and flow cytometry.Results The Lck-Cre×Spi1flox/flox mouse genotype was stably inherited.Compared with Spi1flox/flox mice,the expression level of PU.1 was significantly reduced in splenic T cells of Lck-Cre×Spi1flox/flox mice.Conclusion In this study,the T lymphocyte-specific Spi1 knockout mice was successfully constructed by applying Cre/LoxP system and CRISPR/Cas9 technology,which provided a reliable an-imal model for the subsequent experiments of the specific role of PU.1 in T cell-related diseases.

Objective : The live cell application was used to observe the process of phagocytosis of endometrial cancer cells by macrophages, and flow cytometry was used to detect the effects of macrophages engulfing tumor cells on activation of cytotoxic T cell. Methods : Ishikawa cells and THP1-induced macrophages were labeled with CFSE fluorescent probe and CD11 b respectively, and then mixed and seeded on a glass imaging dish.The live cell application was performed to record the phagocytosis of Ishikawa cells by macrophages within 120 minutes.Flow cytometry was used to detect the effect of macrophages engulfing tumor cells on activation of cytotoxic T cell. Results : The green fluorescence of Ishikawa cells was taken up by macrophages after the co-cultured two types of cells were in contact with each other, and macrophages were able to engulf multiple Ishikawa cells continuously.Macrophages that engulfed Ishikawa cells could induce activation of cytotoxic T cell. Conclusion The live cell application was successfully conducted to construct an in vitro model of phagocytosis of tumor cells by macrophages, which provided a feasible experimental method for detecting the dual killing process of macrophages and T cells on tumor cells.

Objective: To obtain chimeric antigen receptor macrophages ( CAR-M) targeting HER2 stably transfected． Methods : CAR lentivirus vector targeting HER2 was constructed and infected with human monocytic leukemia cell line (THP-1) ．CAR THP-1 cells with green fluorescent labeling were selected by sorting flow cytometry and continued to be cultured in vitro．The CAR THP-1 cells targeting HER2 were co-cultured with the endometrial cancer cell line Ishikawa with negative and positive HER2 expression，and their targeted phagocytosis of CAR-M to HER2 positive tumor cells was detected by imaging flow cytometry ，and the targeted phagocytosis efficiency of CAR-M to HER2 positive tumor cells was detected by flow cytometry. Results : CAR lentivirus infection with THP- 1 cells was less efficient ; After co-culture with cancer cells，flow cytometry and imaging flow cytometry showed that CAR THP-1 cells had enhanced phagocytosis of HER2 positive Ishikawa cells compared with the empty body group (P＜0. 01) ． Conclusion In this experiment，CAR THP-1 cell line targeting HER2 was established by constructing CAR lentivirus vector and transfecting THP-1 cells ，and it was proved that CAR THP-1 could phagocytize HER2 positive Ishikawa cells through specific targeting.