Fig 6. Schematic model of adhesive microvilli formation.

(A) Upon activation of endothelial cells, ICAM-1 is upregulated and processed into the plasma membrane; it associates with tetraspanin CD9 to form clusters 2-dimensional. (B) The clusters (or: endothelial adhesive platforms EAPs also contain JAM-A, which is not depicted here) recruit f-actin, potentially through a RhoG dependent mechanism. (C) The clustered adhesion platforms are propelled upwards by typically 160 ± 80 nm, thereby increasing the interaction probability with leukocytes. (D) Upon leukocyte contact, the microvilli are further elongated to develop a full docking structure with long filopodia engulfing the leukocyte.