LAD PBLs express functional LFA-1 but fail to exhibit LFA-1–dependent adhesion to ICAM-1 in response to chemokine. (A) SDF-1–triggered LFA-1–mediated adhesion of PBLs to ICAM-1 at stationary contacts. (i) Resistance to detachment by incremented shear forces developed by control or LAD patient PBLs settled for 1 minute at stasis on ICAM-1 coimmobilized at 0.25 μg/mL with inactivated SDF-1 (-) or intact SDF-1 (+), each at 2 μg/mL. (ii) FACS staining of LFA-1 using the αL subunit–specific mAb TS2.4. (B) Spontaneous LFA-1–mediated adhesion to high-density ICAM-1 (0.75 μg/mL) developed upon 1-minute static contact of control (□) or LAD patient (○) PBLs. Level and strength of adhesion was determined by the relative resistance of the different PBLs to detachment by incremented shear stresses. The percentage of adherent cells remaining bound to ICAM-1 at a shear stress of 6.25 dyne/cm² that underwent spreading on the ligand is shown in parentheses. Further details are outlined in “Materials and methods.” (C) PMA-triggered adhesion and resistance to detachment developed on ICAM-1–IgG (0.25 μg/mL overlaid on protein A) upon 1-minute static contact of control or LAD PBLs. The percentage of adherent cells that underwent spreading is shown in parentheses. Results in panels A-C are given as mean ± range of determinations in 2 fields of view, and the experiment shown is representative of 3 independent tests.