CROSS-LINKING OF ICAM-1 INDUCES COSIGNALING OF AN OXIDATIVE BURST FROM MONONUCLEAR LEUKOCYTES

Cell adhesion molecules were first described as accessory molecules si mply to bridge one cell to another. More recently, it has been realize d that these molecules also transmit signals from outside of the cell to inside. We show that cross-linking of the ICAM-1 on the cell membra ne with anti-ICAM-1 mAb and F(ab')(2) fragments of goat anti-MlgG in t he presence of suboptimal levels of the bacterial peptide FMLP results in co-stimulation of an oxidative burst from CD14 expressing PBMCs. T he amplitude of the oxidative response was less than the oxidative bur st induced by CD18 cross-linking, whereas the response was more prolon ged. On the other hand, cross-linking by anti-L-selectin mAb plus F(ab ')(2) fragments of goat anti-MlgG induced a minimal oxidative burst th at was not significantly greater than the response generated by anti-L -selectin mAb alone. The addition of an excess of soluble ICAM-1 to co mpete for the anti-ICAM-1 mAb inhibits the oxidative burst in response to ICAM-1 cross-linking but not to CD18 cross-linking. These results suggest that ICAM-1 is capable of delivering a transmembrane signal in to CD14-positive PBMC.