Cytokine production by peripheral blood mononuclear cells following birch-pollen immunotherapy

We studied the Th2/Th1 balance by short-term stimulation of peripheral bloo d mononuclear cells (PBMC) isolated during the pollen season from seven all ergic patients treated with conventional birch-pollen immunotherapy (IT) fo r 18 months, eight matched allergic control patients and 10 non-atopic indi viduals. The PBMC were cultured for 7 days with birch-pollen extract (BPE) or tetanus toroid (TT), and then restimulated with PHA and PMA to induce hi gh IL-5, IL-10 and IFN-gamma production. The serum levels of birch-pollen-s pecific IgG and IgG4 were significantly elevated after IT treatment. The pr oliferative response to BPE was significantly enhanced in the allergic cont rol group, but not in the IT-treated group. compared to the non-atopic grou p (P < 0.05). Birch-pollen-specific IL-5 production was significantly enhan ced in both the IT-treated group and the allergic control group (P < 0.01 - 0.05). Furthermore, both the IT-treated group and the allergic control gro up had a cytokine profile to BPE significantly more Th2 polarized (high IL- 5/IFN-gamma ratio) than to TT (P < 0.05 and P < 0.01, respectively). No dif ferences in IL-10 production between the three study groups were observed. The Th2/Th1 balance in vitro correlated with the serum concentrations of bi rch-pollen-specific IgE (r = 0.60, P < 0.05), and in the IT-treated group, also with the IgG and IgG4 levels (r = 0.79, P < 0.05 and r = 0.86, P < 0.0 5, respectively). We conclude that conventional birch-pollen IT does not le ad to changes in the cytokine profile of the circulating pool of allergen-s pecific T cells during birch-pollen season. However, induction of periphera l T-cell tolerance and increased production of specific IgG and IgG4 might be part of the mechanisms of IT. (C) 2000 Elsevier Science B.V. All rights reserved.