Distinct Epitopes on CD13 Mediate Opposite Consequences for Cell Adhesion

Figure 1

MAbs C and E inhibit homotypic aggregation of monocytic cells induced by anti-CD13 mAb 452. (a) U-937 cells in 96-well plates were incubated for 1 h at 37°C with a control IgG, or the monoclonal antibodies C or E, before addition of HA-inducing activating anti-CD13 mAb 452 (1 µg/ml). Representative images of HA were obtained two hours after addition of mAb 452. (b) U-937 cells in 96-well plates were incubated with indicated concentrations of a control IgG, mAb C, or mAb E, for 1 h at 37°, before addition of HA-inducing mAb 452 (1 µg/ml). Percent of aggregated cells was determined 2 h after addition of mAb 452. Percent aggregation (aggregation index, AI) = [number of cells detected by the software as blue colonies in each image (aggregated cells)/total number of cells detected × 100]. (c) Detachment of homotypic aggregates of U-937 cells. U-937 cells were incubated for 2 hrs at 37°C with anti-CD13 mAb 452 to induce aggregation. Then, inhibitory mAbs C or E or control IgG were added (time = 0), and incubation was continued for 24 h at 37°C. Percent aggregation was determined after 2, 16, and 24 h, as described above. The graphs represent the arithmetic mean ± SD of five (b) or three (c) independent experiments. ; .

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