Human leukocytes express ephrinB2 which activates microvascular endothelial cells.

EphrinB2-EphB4 interaction modulates the migration/adhesion of various cell types, including endothelial cells (EC) and peripheral blood leukocytes (PBLs). We hypothesize that the Ephrin/Eph signaling mechanism plays a role in mediating EC/leukocyte interactions during inflammation. PBLs were isolated from human blood, stimulated with inflammatory mediators, and total RNA or protein assayed for EphrinB2 expression. PBLs demonstrated differential expression profiles of EphrinB2 mRNA or protein, depending on cell subtype and stimulus. Human iris tissue and iris EC (HIEC) were examined for the expression of EphB4 mRNA and protein. Some blood vessels were EphB4(+), while stimulation of purified HIEC did not alter their expression of EphB4. HIEC treated with sEphrinB2/Fc from 0 to 60min did exhibit changes in their phospho-Erk1/2 levels. These observations indicate that stimulated lymphocytes express EphrinB2, which has the potential to activate EC. This suggests a novel mechanism by which EC and lymphocytes communicate to regulate cell activation/migration during inflammation.