Interestingly, Ehirchiou et al. [44] found that TH17 cells in lymph nodes may negatively interfere with tolerance induction to fed allergens, which suggests that IL-17A could be involved in the allergic airway sensitization

in our i.n. model. Apparently, the youngest mice had augmented airway responses compared with older mice. In both the i.p. (10 μg) Decitabine concentration and i.n. model, the youngest mice had higher BALF eosinophil influx and higher cytokine secretion than older mice. In the i.n. model, the OVA-only immunized 1-week-old mice also presented with increased OVA-specific IgG1 levels accompanied by a neutrophil inflammation in BALF. It may be argued that endotoxin contamination of the OVA could have an inflammatory effect particularly in the youngest mice. However, acute lung responses to endotoxin did not differ between newborn and adult mice [45], which argue against endotoxin as an explanation for the observed age differences. Allergen doses that

induce tolerance in adult rodents may, when applied mucosally in newborns, induce IgE sensitization [46, 47]. However, we did not observe effects on OVA-specific IgE after i.n. exposure to OVA alone. If the inflammation in mice sensitized at 1 week of age may be ascribed to an IgG-immune-complex-induced reaction cannot be defined from this study, but would explain the neutrophil-dominated AZD6244 price inflammation [48, 49]. Whether the general propensity to elevated inflammation in very young mice may be

STK38 linked to early onset of allergy and asthma in children remains to be determined. Further, half of children with early-onset asthma outgrow their disease [50]. It could be speculated that this is because of the maturation of the immune system, because bronchial hyperreactivity and airway inflammation persisted for a shorter time in mice sensitized when newborn compared to when sensitized as 8 weeks old [34]. Although ‘new’ allergy can occur throughout life, generally, allergy prevalence and severity tend to decrease after young adult life [51], and TH2-type responses may weaken with age [52]. Immunological ageing studies have included mice of much higher age than the present study. However, our study clearly demonstrates that age may exert a pronounced effect on experimental allergy even in mice up to 5–6 months of age. Further, allergy responses in female and male mice may be affected differently by age and allergen doses. The study also indicates that to develop appropriate models of allergy in children, adults and aged humans, good knowledge of age-related effects in human allergic diseases is required. The data presented here demonstrated that age, sex and immunization dose interact to be significant determinants of experimental allergy. Therefore, optimal modelling must be performed to mimic human disease. The study was financed by The Norwegian Research Council.