Requirement of uPAR for leukocyte adhesion in response to VLA-4 ligation.
(A) Myelomonocytic HL60 cells were treated with medium alone (open bar) or with mAb K20 (20 μg/mL, filled bars) for 30 minutes at 37°C. Following washing, adhesion to immobilized vitronectin was performed in the presence or absence of mAbs anti-uPAR R3 (blocking), R4 (nonblocking), or anti-αvβ3 LM609 (20 μg/mL) as described. Values represent the mean ± SEM of 3 independent experiments. (B) Myelomonocytic HL60 cells were treated with medium alone (open bars) or pretreated with phosphatidylinositol-specific phospholipase C (0.5 U/mL) for 90 minutes at 37°C (filled bars), washed, and incubated for 10 minutes in the absence or presence of soluble intact uPAR (D1-D3, 16 nmol/L), the truncated form of uPAR (D2/D3, 20 nmol/L) lacking domain 1, or with soluble tissue factor pathway inhibitor (sTFPI; 16 nmol/L), followed by incubation for 20 minutes with medium, soluble VCAM-1–Fc (40 μg/mL), or mAb K20 (15 μg/mL) as indicated. Following washing, adhesion to endothelial cell monolayers was performed as described. Values are displayed as percentage of control (no pretreatment, 100%) and represent the mean ± SEM of 3 independent experiments. *Indicates P < .01 compared with the respective medium control; n.s., not significant (P > .05).
