Activation of PBMC adhesion to endothelium is induced by SS RBC LW and CD44. Inhibition of PBMC interaction with epi-treated SS RBCs was attempted by preincubation of SS RBCs with antibodies against the RBC receptors CD47, LW, and CD44; P3 was used as a nonreactive control antibody. Adhesion of PBMCs coincubated with such epi-treated SS RBCs was then assayed. Results are presented as percentage of adherent PBMCs at a shear stress of 1 dyne/cm². Error bars show SEM of 3 different experiments. *P < .001 compared with unstimulated PBMCs; **P < .001 compared with PBMCs coincubated with SS RBCs preincubated with P3, then treated with epi.