Leukocyte phenotype changes induced by specific immunotherapy in patients with birch allergy.

BACKGROUND The underlying mechanisms of allergen-specific immunotherapy (SIT) are not fully understood. OBJECTIVES The present study aimed to investigate how leukocyte phenotypes are affected by SIT. METHODS Blood samples were taken from 10 patients with birch pollen--induced allergic rhinitis before, during, and immediately after SIT. Further samples were obtained after 1 year and 3 years. All samples were analyzed by flow cytometry and leukocyte differentiation. RESULTS SIT caused a decrease in cell-bound immunoglobulin (Ig) E on granulocytes, along with a corresponding increase in the high-affinity IgG receptor. Accordingly, a lower level of allergen-specific IgE was found after 3 years. The treatment induced a decrease in neutrophil CD1 1b levels, a shift in monocyte subsets, and an increase in the number of activated T lymphocytes, manifested as an upregulation of CD69 and CD98, and an expansion of the CD4+CD25+ T-cell pool. CONCLUSION The present study shows that the clinical effects of SIT are mirrored by systemic changes in cellular events and in antibodies, and offers new targets for immunomodulation.