ACTIVATION OF B-LYMPHOCYTES DURING POLLEN SEASON - EFFECT OF IMMUNOTHERAPY

Background B-lymphocytes play an important part in the allergic reacti on as producers of IgE antibodies. Objective To investigate the cell s urface expression of the activation antigens CD23, CD40 and HLA-DR on B-lymphocytes in birch pollen allergic patients before and during birc h pollen season and to study the effect of immunotherapy. Methods The study included 24 birch pollen allergic patients half of whom were tre ated with immunotherapy against birch pollen before the start of the s eason. Eleven of the 24 patients had asthma. Blood samples were taken and lung function was registered before the season began and before th e immunotherapy treatment in January to February and during the season in May. The relative number of B-lymphocytes (CD19(+)) of the lymphoc yte population and the cell surface expression of CD23, CD40 and HLA-D R on B-lymphocytes was measured by the use of flow cytometry. Results In the control group of patients the relative number and concentration of B-lymphocytes, the cell surface expression of CD23, CD40 and KLA-D R on B cells, and the serum concentration of IgE increased during seas on compared with before season. In contrast, in the immunotherapy trea ted patients no changes in the number of B cells or cell surface expre ssion of CD23, CD40 and HLA-DR were demonstrated. Conclusion The eleva ted expression of CD23, CD40 and HLA-DR on B cells, combined with incr eased levels of IgE in allergic patients during season could be explai ned by the effect of cytokines produced by activated TH2 cells. A shif t from TH2 to TH1 cells might be the mechanism after the absence of si gns of B-cell activation in immunotherapy treated patients. The preven tion of increased cell surface expression on B cells by immunotherapy may constitute a significant mechanism behind the beneficial effects o f immunotherapy in the treatment of pollen atopy.