Role of PECAM-1 homophilic interaction in inducing survival of CD34⁺ cells.

CD31⁺CD34⁺ (■) or CD31⁻CD34⁺ (░) cells were allowed to adhere to PECAM-1⁺–transfected ECV304 (P-ECV304; A) or to the mock-transfected ECV304 cell line (B), in the absence or presence of the F(ab′)₂ of the anti–PECAM-1 (M89D3) or the anti–ICAM-1 (14D12D2) mAbs, then collected after 48 hours of culture, stained with PI as in Figure 2, and run on a FACSort. We analyzed 10⁴ cells per sample; results are plotted as percentages of apoptotic (DNA content < 2n-diploid) cells. (C) Percentage of apoptotic cells, upon ligation of PECAM-1, CD34, β2-integrin (obtained with 5 μg/mL of the M89D3, HPCA-1, or JT90 mAb, respectively, followed by 10 μg/mL GAM). Murine Ig plus GAM were used as controls. Mean values ± SDs from 6 different experiments are shown.