The selective binding and transmigration of monocytes through the junctional complexes of XXXX endothelium.

@entity1 @entity575
@entity1 monocytes show a high affinity for vascular endothelium both in vitro and in vivo. To explore monocyte-endothelial interaction in greater detail, we have developed a new in vitro model for growth of @entity1 endothelial cells (EC). @entity1 umbilical vein EC (HUVEC) cultured upon collagen gels form confluent monolayers of EC that bind @entity575 at their intercellular border similar to cells in situ. Intercellular junctional structures, both adherens and tight junctions, were identified. In contrast, HUVEC grown on plastic surfaces did not stain with @entity575 . The @entity575 -staining characteristic of EC-collagen monolayers was reversible and related to their in vitro maturation and senescence. @entity575 staining of EC borders provided a grid by which the location of monocyte binding to the luminal surface of individual EC could be assessed. Using this technique, we found that monocytes preferentially bound to the margins of EC, in approximation to the @entity575 -staining junctions. These results suggest that EC determinants recognized by monocytes occur in a unique topographical distribution on the apical face of EC. After binding, monocytes migrated through the EC monolayers at high basal rates. The lack of penetration of collagen gels in the absence of an EC monolayer suggested the generation of EC-specific chemotactic signal(s). Monocytes were observed to pass between EC without evidence of disruption of the monolayer. @entity575 stain remained present during all phases of migration, and under transmission electron microscopy, junctional complexes were found proximal to monocytes that had just completed their passage through the monolayer. After orientation to the basal surface of the EC monolayer, monocytes migrated randomly into the underlying collagen gel. Monocyte adherence, penetration, migration, and long term survival can be studied under these conditions.
