The adhesion of HbSS RBCs to immobilized ICAM-1 is mediated by fibrinogen and is inhibited by LMWH. (A) Mean percentages of RBCs adherent to immobilized ICAM-1 following the treatment of blood samples with anti-α4β1 or anti–LFA-1 antibodies or the treatment of microchannels with recombinant human β2 protein in 5 experiments. With vehicle treatment, a mean of 100% of RBCs adhered to immobilized ICAM-1. No significant reduction in HbSS RBC adhesion to immobilized ICAM-1 was observed (P > .05). (B) Treatment of microchannels with fibrinogen decreased HbSS RBC adhesion to ICAM-1 in a concentration-dependent manner. Shown are mean percentages of adherent RBCs after treatment with 1, 5, 10, or 20 mg/mL fibrinogen (n = 5). (C) Treatment of blood samples with LMWH significantly inhibited HbSS RBC adhesion to ICAM-1. Shown are mean percentages of adherent RBCs following pretreatment with 0.1, 1, or 5 μg/mL LMWH in 5 experiments. The P values were calculated using 1-way ANOVA with the Dunnett post hoc test. Error bars represent ± SEM.