In vitro method establishment for detecting monocyte phagocytosis of sensitized RBCs by flow cytometry

Abstract

Objective To establish an experimental method for detecting phagocytosis of sensitized red blood cells in vitro by flow cytometry. Methods Mononuclear cells were isolated from the peripheral blood of blood donors and cultured in a cell incubator for 1 hour, and then adherent monocytes were isolated and obtained. Dib-positive red blood cells (RBCs) were labeled with PKH26 and then sensitized with IgG anti-Dib. The sensitized RBCs were added to monocytes for in vitro phagocytosis assay. Monocytes were labeled with FITC anti-human CD14, then phagocytosis was measured by flow cytometry, and the phagocytic efficiency was calculated. The method was used to detect the phagocytic efficiency of monocytes on human IgG anti-D sensitized RBCs with different titers. Results The phagocytic efficiency of monocytes was averaged at 5% (1.2%~7.6%, SD 3.30) versus 81% (71.4%~92.7%, SD 8.65) in the negative versus positive control group, respectively. Phagocytic activity of monocytes mediated by anti-D was correlated with the antibody titer. The phagocytosis efficiency was within 10% when the antibody titer was lower than 32 and increased sharply when the titer was between 32 to 128, it entered a plateau and stabilized at 80% at the titer above 256. Conclusion A detection platform for detecting phagocytosis-sensitized RBCs in vitro by flow cytometry has been successfully established. It can be used to assess the clinical significance of red blood cell allotype or autologous IgG antibodies.

Keywords

• monocytes
• phagocytosis
• flow cytometry
• monocyte monolayer assay (mma)