Ephrin-B3 binds specifically to B lymphocytes in blood and induces migration

Eph receptors and ephrin ligands have been shown to be differentially expressed on leucocytes. Here, we show that one member of the ephrin-B subfamily of ephrins, ephrin-B3, specifically binds to B lymphocytes in blood. No binding was observed to T lymphocytes or monocytes. The ephrin-B3 binding receptor on B lymphocytes is so far not identified, but our results here indicate that ephrin-B3 binds to a protein not belonging to the Eph receptor family. Recently, we have shown that ephrin-B3 binds to a sulphated cell surface receptor on HEK293T cells and that this binding can be blocked with heparin. Ephrin-B3 binding to B lymphocytes is partially affected by heparin, and a basic amino acid in the extracellular juxtamembrane region, Arg-188, is here shown to be involved in this binding. The functional consequence of ephrin-B3 binding to B lymphocytes is induced migration, in particular of the memory cells. To conclude, ephrin-B3 binds to B lymphocytes, most likely via a non-classical receptor, and induces migration of the memory B cell subpopulation.