Brain-derived neurotrophic factor selectively enhances allergen-specific IgE production

We studied the effect of brain-derived neurotrophic factor (BDNF) on in vitro Japanese cedar pollen (JCP)-specific IgE production by mononuclear cells from atopic keratoconjunctivitis patients with JCP allergy. BDNF enhanced JCP-specific IgE production in a dose-dependent fashion in cultures of mononuclear cells stimulated with JCP, and maximal enhancement was achieved at 10 ng/ml. In contrast, BDNF had no effect on JCP-specific IgA or IgG4 production. On the other hand, other neurotrophins, NGF, NT-3, or NGF failed to enhance JCP-specific IgE production. Moreover, anti-BDNF mAb specifically blocked BDNF-induced enhancement of JCP-specific IgE production. Study for cytokine production revealed that BDNF decreased production of Th1 cytokines, IFN-γ and IL-12, while it had no effect on production of TH2 cytokines, IL-4, IL-10 and IL-13, in cultures of mononuclear cells stimulated with JCP. These results indicate that BDNF relatively skews cytokine pattern toward Th2 type. Collectively, BDNF may increase allergen-specific IgE production, which may in turn aggravate allergic symptoms.