Lu/BCAM amino acid residue R338 is critical for laminin-α5 binding. (A) Laminin-α5–coated ibidi chambers and erythrocytes were treated with neuraminidase and compared with nontreated erythrocytes (n = 4), and adhesion frequency to laminin-α5 was assessed at 0.2 dyn/cm². (B) Various Lu/BCAM domains were aligned to SIGLEC sequences that are centered around the arginine residue critical for interaction with sialic acid residues. (C) Flow cytometry histogram comparing expression of Lu-WT (red) and Lu-R338A (blue) in transfected K562 cells. (D) Adhesion of K562 cells transfected with Lu-WT and Lu-R338A to laminin-α5–coated ibidi chambers (n = 3). K562 cell adhesion strength was measured to correct for variation between controls. Adhesion strength was defined as the percentage of cells that remain attached after gradually increasing flow shear from a static to 0.2 dyn/cm² up to a maximum of 2.5 dyn/cm². (E) Flow cytometric comparison of control (light gray), Lu-WT-Fc (red), and Lu-R338A-Fc (blue) coated protein-G beads. (F) Adhesion strength of Lu-WT-Fc and Lu-R338A-Fc–coated protein-G beads (n = 3). *P < .05; **P < .01; ***P < .001.