Loss of sialic acids on the erythrocyte membrane activates Lu/BCAM. (A) Representative micrograph of adhesion of healthy erythrocytes (top panel; original magnification ×10) and sickle erythrocytes (lower panel) to a laminin-α5–coated ibidi chamber at 0.2 dyn/cm. (B) Quantification of adhesion frequency of old and young erythrocytes to laminin-α5 at 0.2 dyn/cm² (n = 3). Percoll dilutions were stacked in a 15-mL tube; erythrocytes isolated from the fraction denser than 1.096 g/mL Percoll were defined as dense and old erythrocytes (roughly 3% of total red blood cell [RBC]), whereas erythrocytes lighter than 1.060 g/mL Percoll are here defined as light and young erythrocytes (roughly 0.75% of total RBC). (C) Biotinylated Maackia amurensis lectin type II (MA) was used to quantify α2,3-linked sialic acid (SIA) by flow cytometry (Data shown as mean fluorescence intensity [MFI] and normalized [Norm.] to control erythrocytes [aaRBC].). (D) Membrane sialic acid was removed from control erythrocytes by V cholerae neuraminidase (N'ase RBC), and adhesion frequency was assessed at 0.2 dyn/cm² (n = 5). Specificity was addressed using an Lu/BCAM blocking polyclonal antibody. (E) Sickle erythrocyte (ssRBC) adhesion frequency to laminin-α5 at 0.2 dyn/cm², either treated or not treated with neuraminidase for 30 minutes at 37°C (n = 5). *P < .05; ***P < .001.