Changes of Phenotype and Phagocytosis of Peritoneal Macrophages in Mice Infected with the Larval-stage of Echinococcus granulosus

Objective: To investigate the phenotype and phagocytosis changes of the peritoneal macrophages (Mφ) in mice infected with the larval-stage Echinococcus granulosus, and explore the role of Mφ in the responses to parasite infection. Methods: Twenty-four female BALB/c mice (age of 6-8 weeks) were randomly assigned into control group and infection group (n=12 in each group). The mice in the infection group were intraperitoneally injected with 2 000 protoscoleces, while the control mice were injected with equal volume of PBS. Five months after infection, the peritoneal mononuclear cells were collected, and the percentage of Mφ and the expression of surface markers CD40, CD80, CD86, and major histocompatibility complex Ⅱ (MHCⅡ) were determined by flow cytometry. The absorbance（A490 value） of Mφ at different concentrations（1×106, 5×105, 1×105） was determined by the neutral red assay to evaluate the phagocytic ability of Mφ. Results: The Mφ constituted（30.40±3.15）% and（20.75±5.91）% in mononuclear cells in the infection and the control groups, respectively. The percentages of Mφ expressing CD40, CD80, CD86, and MHC Ⅱ were（45.33±5.51）%, （61.00±10.61）%, （56.88±10.66）% and （27.00±3.82）% in the infection group, which were all significantly higher than those in the control ［（41.43±6.19）%, （59.23±8.65）%, （10.91±1.82）% and （13.67±3.01%）］ （P<0.05）. The A490 values of Mφ at 1×106, 5×105, 1×105 were 0.41±0.03， 0.24±0.05 and 0.16±0.01 in the infection group, which were significantly lower than those in the control （0.61±0.15, 0.47±0.07 and 0.18±0.01）（P<0.01）. Conclusion: The phagocytic ability of peritoneal Mφ is dramatically weakened after infection, but the expression of activation-associated surface markers is significantly up-regulated after infection.