With an i.p. sensitization model, we found that mice immunized when 1 week old responded differently to the immunization doses compared to the two groups immunized at older ages. This
led to the general observation that for the 0.1 μg OVA immunization dose, OVA-specific IgE, IgG1, cytokine and inflammatory find protocol cell responses increased with age. In contrast, following immunization with 10 μg OVA, cytokine secretion and inflammatory cells responses in BALF decreased with age, while antibody production was comparable for all age groups. These observations could be explained by the fact that in 1-week-old mice, significant antibody, cytokine and inflammatory responses were only induced following immunization with the 10-μg dose. Further,
eosinophil numbers and cytokines levels were found at strikingly higher levels than in older mice, while IgE and IgG1 levels were similar Selleck Deforolimus to those in older mice. While the i.p. immunization doses differed, the airway OVA challenge dose was comparable for all groups. We observed that the antibody levels both before and after airway challenges were affected comparably by allergen dose, sex and age. The airway challenges, thus, only increased the antibody production. This suggests that the age at immunization and not the age at airway challenge determined the antibody response as observed previously also for airway hyperresponsiveness and eosinophil inflammation . In adolescent and sexually mature mice, the low immunization dose stimulated stronger antibody, cytokine and eosinophil responses than the high i.p. immunization dose. Thus, a low sensitization dose may provide a better tool for modelling allergy in adult mice. These findings are in line with previous dose–response investigations showing that lower doses stimulate IgE and higher doses stimulate IgG responses [2, 22, 23]. Ohki et al.  observed that i.p. immunization with 10 μg compared with 1000 μg OVA resulted in higher allergen-specific IgE and inflammatory responses in both 3-day- and 8-week-old mice. Thus, one
should be aware that using a high immunization dose in adult (and possibly also young) mice may result in suboptimal IgE responses, and inflammatory cells and cytokine levels may even decrease when older mice are used. After the booster, all Methisazone mice in our study immunized with 1000 μg OVA suffered from severe anaphylactic shock and had to be terminated before any tissue samples could be collected (see Materials and method section). In the i.p. sensitization model, sex differences were only seen when using the ‘optimal’ 0.1-μg immunization dose; IgE production was higher in 6-week-old female mice than in male mice, and IL-5 and IL-13 secretion was generally higher in the female sex. Thus, sex differences on IgE were only found in sexually mature animals, which supports the apparent influence on allergy by sex hormones observed in previous studies [25, 26].