ALLERGEN-INDUCED CYTOKINE PROFILES IN TYPE-I ALLERGIC INDIVIDUALS BEFORE AND AFTER IMMUNOTHERAPY

Allergen immunotherapy (IT) involves subcutaneous injections of increa sing doses of specific allergen over a period of time. It is recognise d as highly effective in the treatment of patients with allergic rhini tis. However, the specific immunological mechanisms by which IT achiev es its effect have not been fully elucidated. Recent studies have show n that the clinical effects following IT of allergic individuals is co ncomitant with a reduced production of IL-4 by allergen specific CD4() T-cells. The aim of the present study was to gain better knowledge a bout the immunological mechanisms by which IT exerts its beneficial ef fects. For this purpose, peripheral blood mononuclear cells (PBMC) fro m ten individuals receiving birch allergen or placebo in an IT-study p erformed in a double-blind manner, were analysed for IL-4, IFN-gamma, IL-S and IL-10 mRNA expression at the onset of the study and during th e pollen season, during treatment. Both spontaneous and in vitro aller gen-induced cytokine mRNA expression was analysed using reverse transc riptase-polymerase chain reaction (RT-PCR). Spontaneous expression of IL-4 mRNA could be detected in most of the allergic patients, but not in healthy donors. The IT-treated patients showed a decrease in the sp ontaneous expression of IL-4 mRNA during the pollen season as compared to at the onset of the study, while in patients receiving placebo the IL-4 mRNA expression increased or remained unchanged. Similar results were obtained after in vitro stimulation with allergen. This was in c ontrast to the results for IFN-gamma, which was readily detected in bo th patient groups with no significant differences between the groups a t either timepoint. IL-5 was shown to be increased during the pollen s eason in both groups and thereby presumably not affected by allergen I T. Taken together, these observations suggest that the cytokine profil es in circulating T lymphocytes change as a consequence of allergen TT . (C) 1997 Elsevier Science B.V.