COMPARISON OF HUMAN EOSINOPHIL AND NEUTROPHIL LIGANDS FOR P-SELECTIN - LIGANDS FOR P-SELECTIN DIFFER FROM THOSE FOR E-SELECTIN

Eosinophils (EOS) and neutrophils (PMN) display different patterns of accumulation during various inflammatory reactions. We hypothesized th at EOS and PMN may differ in their ligands for P-selectin, and that th ese ligands may differ from those previously identified for E-selectin . Recombinant human P-selectin was immobilized on plastic surfaces and adhesion of Cr-51-labeled human EOS or PMN was compared. EOS and PMN adhered in a concentration-dependent fashion, with similar maximal net adhesion, Preincubation with a blocking P-selectin antibody inhibited adhesion of both cell types, whereas a non-blocking antibody did not. To determine if the counterligands were sialylated proteins, cells we re treated with various glycosidases and proteases before testing adhe sion. Neuraminidase treatment markedly inhibited binding of both cell types, while endo-beta-galactosidase had no significant effect. Pretre atment with several proteases reduced adhesion of both cell types, alt hough they consistently caused a greater inhibition of PMN binding tha n EOS binding. To determine whether the P-selectin ligands were surfac e structures whose expression or function may be altered by cell activ ation, leukocytes were pretreated with various stimuli; only platelet- activating factor (PAF) treatment reduced the capacity of leukocytes t o adhere to P-selectin. Thus, the counterligands for P-selectin on EOS and PMN are similar sialylated, protease-sensitive, endo-beta-galacto sidase-resistant structures, whose function and/or expression is reduc ed following treatment with PAE These characteristics are clearly diff erent than those reported for EOS and PMN ligands for E-selectin, and suggest disparate roles for P-selectin and E-selectin during EOS and P MN recruitment during inflammatory responses in vivo.