Identification of an active sequence within the first immunoglobulin domain of intercellular cell adhesion molecule-1 (ICAM-1) that interacts with fibrinogen

Monocytic cells bind fibrinogen (fg) through integrin α(M)β₂. fg- bound monocytic cells demonstrate an enhanced adhesion to endothelial cells, which is dependent on intercellular adhesion molecule-1 (ICAM-1). Our studies differentiate fg interactions with stimulated and resting endothelial cells, which are ICAM-1 dependent and independent, respectively. This report documents a direct interaction between fg and intact ICAM-1 and with a two- Ig domain form of ICAM-1. A small region within the first Ig domain of ICAM- 1, ICAM-1-(8-21) (KVILPRGGSVLVTC), was identified to interact with fg in a specific and selective manner. ICAM-1-(8-21) bound to plasmin-derived fg fragments X, D100, and D80 but not to fragment E. Consistent with this finding, fg γ-chain peptide, fg-γ-117-133, blocked fg interaction with ICAM-1-(8-21). ICAM-1-(8-21) peptide and antibodies directed against ICAM-1- (8-21) also blocked the adhesion and binding of ICAM-1-bearing Raji cells with fg. ICAM-1-(8-21) and fg-γ-117-133 are likely to be one of the contact pairs mediating fg-ICAM-1 interactions.