Monocytic cell adhesion to intact and plasmin-modified fibrinogen: Possible involvement of Mac-1 (CD11b/CD18) and ICAM-1 (CD54)

beta2-integrin Mac-1 and immunoglobulin-like ICAM-1 adhesion molecules are expressed by monocytes and both known to bind fibrinogen and its degradation products. Here, we investigated whether fibrinogen cleavage with plasmin modulates the adherence of monocytic cells and what types of adhesion molecules are involved. Using several cell types, characterized by different patterns of Mac-1 and ICAM-1 expression, and monoclonal antibodies against beta (2)-integrins and ICAM-1 we demonstrate, that fibrinogen cleavage evokes gradual decrease in beta (2)-integrin-dependent cell adhesion. Furthermore, generation of the early degradation products, fragments X and Y, by minimum cleavage of fibrinogen stimulates cell adhesion, mediated by ICAM-1.