A novel immunoglobulin superfamily junctional molecule expressed by antigen presenting cells, endothelial cells and platelets.

The architecture of lymphoid microenvironments depends upon complex interactions between several stromal cell types. We describe in this report the cloning of a cDNA which encodes a novel membrane molecule containing two external Ig-like domains. It is expressed at the junction between endothelial cells including HEV. It is also expressed by platelets and MHC class II+ antigen presenting cells in thymic medulla and T-cell areas in peripheral lymphoid organs. These cells which lack in RelB-deficient mice include tissue-derived dendritic, epithelial cells and macrophages. Thus, this molecule might contribute to the organization of cell junctions in different microenvironments.