(A–C) Human MΦ were transfected with human LGR6 or mock plasmids. Seventy-two hours later, MΦ were plated onto chamber slides (0.1 × 10⁶ cells/well), incubated with 1-nM MaR1 or vehicle for 15 minutes at 37°C, followed by addition of BacLight Green-labeled E. coli to initiate phagocytosis. Fluorescent images were recorded every 10 minutes. Four separate experiments with separate donors were carried out. In each experiment, 4 fields (×20) per condition (per well) were recorded. (A) (Upper left) LGR6 expression monitored by flow cytometry. (Lower left) Representative fluorescence images. Arrows denote MΦ with ingested fluorescent E. coli. Scale bars: 20 μm. (Right) mean fluorescence intensity (MFI)/cell from 1 representative experiment. (B) Kinetics of phagocytosis. Rate (MFI/min) = (MFI_60min – MFI_{20 min})/40 min obtained from the same experiment as in (A). (See Supplemental Figure 6 for results obtained from additional 3 donors.) (C) Percent increases of phagocytosis by MaR1. Results are mean ± SEM (n = 4). *P < 0.05, LGR6 versus mock transfection. (D) Human MΦ were transfected with human LGR6 or mock plasmids. MΦ were incubated with MaR1 (10^–13 to 10^–8 M) or vehicle control for 15 minutes, followed by addition of BacLight Green-labeled E. coli, CFDA-labeled apoptotic PMN, or FITC-labeled STZ. Results are percent increases of phagocytosis above vehicle. Results are mean ± SEM from 3 independent experiments with separate donors and triplicates in each experiment. *P < 0.05; **P < 0.01, versus mock transfection. ^#P < 0.05, ^##P < 0.01; ^###P < 0.001, versus vehicle. (E and F) Human MΦ were transfected with scramble control (SC)-shRNA or human LGR6-shRNA plasmids and phagocytosis carried out as in A. (E) MFI/cell from 1 representative experiment. (F) Percent increases of phagocytosis by MaR1. Mean ± SEM (n = 4). **P < 0.01, LGR6-shRNA versus SC-shRNA transfections. (C, D, and F) Two-way ANOVA with Bonferroni’s multiple comparisons test.