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.

Staphylococcus aureus capsular polysaccharide type 5 conjugate and whole cell vaccines stimulate antibody responses in cattle.

Dairy heifers were immunized subcutaneously with one of four different vaccines which contained preparations of Staphylococcus aureus capsular polysaccharide type 5 (CP5) and a mineral oil adjuvant, or received a placebo containing saline and adjuvant. The vaccine containing a CP5-human serum albumin conjugate (CP5-HSA) and the vaccine with formaldehyde inactivated whole cells expressing CP5, both elicited strong anti-CP5 antibody responses. After two injections three weeks apart and a third injection 10 months later, the mean level and duration of the anti-CP5 antibody response was significantly higher in the whole cell group. No differences were found between the two groups with regard to the relative proportion of IgG subclasses, and the antibody responses to the polysaccharide were composed of both the IgG1 and IgG2. Vaccines containing only free CP5 or CP5 mixed with HSA produced weak and transient humoral immune responses. Only animals vaccinated with the whole cell vaccine or the conjugate vaccine showed responses to CP5 in a lymphocyte proliferation assay conducted one year after the third vaccination. This study indicates that CP5 expressed on the surface of formaldehyde inactivated whole cells, emulsified in an oil adjuvant, gives a strong and long lasting immune response in cattle. The use of conjugation technology, although effective, might not be necessary in order to achieve an immune response against S. aureus CP5 in cattle.