Allergen-induced changes of B-cell phenotypes in patients with allergic rhinitis

We investigated sub-populations of B-lymphocytes in nasal mucosa and peripheral blood of 17 patients with seasonal allergic rhinitis (birch pollen) and 10 controls. The study included provocation with allergen during the non-pollen season, during which no participant used medication. Samples were also taken during the pollen season. Subsets of B-cells as expressed by different CD antigens were investigated by immunohistochemistry on frozen sections and by flow cytometry of peripheral blood. Nasal CD23+ B-cells decreased in allergic patients during provocation, indicating that mature virgin CD23+ B-cells switch into a memory B-cell phenotype with loss of CD23 expression. This indicates differentiation towards cells that can represent a local source for IgE synthesis. No decrease was observed during the pollen season when the patients used medication. Serum IgE was significantly higher in allergic patients on all occasions. The observed up-regulation of CD40 expression on peripheral blood B-cells in allergic patients during the pollen season clearly indicate B-cell activation. Furthermore, a relative increase of CD19+ B-cells was observed in peripheral blood during provocation. Upregulation (by IL-4) of CD40 on B-cells which then may be stimulated by gp39 (CD40 ligand) can constitute an early and important event in the IgE-mediated allergic reaction.