Chronic antigen ingestion protects ovalbumin sensitized mice from severe manifestation of Leishmania major infection.

In the present work, the development of experimental leishmaniasis was examined in sensitized BALB/c mice that were chronically fed with antigen. After an oral challenge with egg white solution, the ovalbumin (Ova)-sensitized mice showed an increase in serum anti-Ova IgE and IgG1 antibodies. Lesions induced by Leishmania major infection were reduced by the ingestion of Ova in sensitized mice, as assessed by reduced footpad growth, lower parasite loads and improved pathological outcome compared to sham sensitized mice. Moreover, such findings were connected to a shift to a Th1 response involving higher IFN-gamma production and serum levels of IgG2a anti-Leishmania antigens. The data appear to corroborate the suggestion that chronic ingestion of an antigen by sensitized mice modulates the immunological system through a shift in cytokine release, exhibiting a healing response and resistance to L. major infection.

A model of chronic IgE-mediated food allergy in ovalbumin-sensitized mice.

Food allergy is most frequently the result of IgE-mediated hypersensitivity reactions. Here, we describe a chronic model in which some of the intestinal and systemic consequences of continuous egg white solution ingestion by ovalbumin-sensitized eight-week-old BALB/c mice, 6 animals per group, of both sexes, were investigated. There was a 20% loss of body weight that began one week after antigen exposure and persisted throughout the experiment (3 weeks). The sensitization procedure induced the production of anti-ovalbumin IgG1 and IgE, which were enhanced by oral antigen exposure (129% for IgG1 and 164% for IgE, compared to sensitization values). Intestinal changes were determined by jejunum edema at 6 h (45% Evans blue extravasation) and by a significant eosinophil infiltration with a peak at 48 h. By day 21 of continuous antigen exposure, histological findings were mild, with mast cell hyperplasia (100%) and increased mucus production (483%). Altogether, our data clearly demonstrate that, although immune stimulation was persistently occurring in response to continuous oral antigen exposure, regulatory mechanisms were occurring in the intestinal mucosa, preventing overt pathology. The experimental model described here reproduces the clinical and pathological changes of mild chronic food allergy and may be useful for mechanistic studies of this common clinical condition.

A model of chronic IgE-mediated food allergy in ovalbumin-sensitized mice

Food allergy is most frequently the result of IgE-mediated hypersensitivity reactions. Here, we describe a chronic model in which some of the intestinal and systemic consequences of continuous egg white solution ingestion by ovalbumin-sensitized eight-week-old BALB/c mice, 6 animals per group, of both sexes, were investigated. There was a 20 percent loss of body weight that began one week after antigen exposure and persisted throughout the experiment (3 weeks). The sensitization procedure induced the production of anti-ovalbumin IgG1 and IgE, which were enhanced by oral antigen exposure (129 percent for IgG1 and 164 percent for IgE, compared to sensitization values). Intestinal changes were determined by jejunum edema at 6 h (45 percent Evans blue extravasation) and by a significant eosinophil infiltration with a peak at 48 h. By day 21 of continuous antigen exposure, histological findings were mild, with mast cell hyperplasia (100 percent) and increased mucus production (483 percent). Altogether, our data clearly demonstrate that, although immune stimulation was persistently occurring in response to continuous oral antigen exposure, regulatory mechanisms were occurring in the intestinal mucosa, preventing overt pathology. The experimental model described here reproduces the clinical and pathological changes of mild chronic food allergy and may be useful for mechanistic studies of this common clinical condition.