EFFECT OF BRONCHIAL ALLERGEN CHALLENGE ON IN-VITRO CYTOKINE RELEASE BY PERIPHERAL-BLOOD MONONUCLEAR-CELLS OF ATOPIC PATIENTS

Background During the pollen season, peripheral blood mononuclear cell s (PBMC) from allergic patients produce increased levels of Th2 cytoki nes after stimulation with allergen in vitro. We have studied the effe ct of a single bronchial provocation test (BPT) of allergic patients t o determine whether allergen challenge in vivo modulates cytokine prod uction by PBMC, after subsequent stimulation with the same allergen in vitro. Methods Twelve atopic asthmatic patients were challenged with the relevant allergen, and their PBMC, isolated before (T0) or 6 (T6) or 24 h (T24) after BPT, respectively, were cultured for 120 h in the presence or absence of the same allergen, after which cytokine product ion was measured by ELISA. Results Allergen-specific activation of the PBMC at T0 resulted in interleukin (IL)-5 and IL-13 production, but n ot in detectable levels of interferon-gamma and IL-4. BPT did not indu ce the secretion of the latter cytokines. However, IL-5 and IL-13 prod uction was significantly decreased at T24, as compared to T0. No stati stically significant differences were found between the production of IL-10 before and after BPT. Conclusions In contrast to the effects of natural challenge with allergen, a decrease in the production of some Th2 cytokines by peripheral blood T cells was observed 24 h after BPT, suggesting a concomitant decrease in the frequency of allergen-specif ic T cells in the circulation.