Allergen-specific increase in interleukin (IL)-4 and IL-5 secretion from peripheral blood mononuclear cells during birch-pollen immunotherapy

Abstract

The mechanisms behind the effects of immunotherapy (IT) with birch-pollen extract are largely unknown. In this pilot study, we measured the cytokine secretion in vitro from peripheral blood mononuclear cells (PBMC) obtained from birch-pollen-allergic patients undergoing IT treatment (n = 4) or placebo administration (n = 4), collected before treatment, 1 and 4 weeks after start of treatment, and during and just after the pollen season (12-14 weeks after start of treatment). The PBMC were stimulated with birch-pollen extract in vitro for 7 days, followed by restimulation with the mitogens phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA) for 24 h, to enhance the production of cytokines. The supernatants were analyzed with ELISA and radioimmunoassay for interferon-gamma (IFN-gamma), interleukin (IL)-4, and IL-5. In the therapy group, we noted an increased secretion of IL-4 and IL-5 from PBMC collected at 4 weeks after the start of treatment (IL-4: 29 +/- 21 pg/ml [day 0] to 374 +/- 448 pg/ml [week 4], mean +/- SD; IL-5: 95 +/- 48 pg/ml to 1147 +/- 697 pg/ml). No increase was seen in the placebo group. During the pollen season, we noted a trend toward increased IL-4 and IL-5 secretion in both groups. We conclude that the temporary increase in serum IgE observed in many IT studies may be a consequence of increased IL-4 production due to the allergen exposure.