We investigated the effect on specific antibody response of naive and sensitized mice orally administrated with low (0.25 mg) or high (10.0 mg) doses of Dermatophagoides pteronyssinus (Dp) extract. We also examined the effect of oral administration of Dp on the production of autoantibodies to immunoglobulin G (IgG) and immunoglobulin E (IgE). Naive and sensitized mice both showed a marked down-regulation of IgE antibody production, regardless of the dose of Dp. We also detected an inhibitory effect of the total IgE levels and the allergen-specific IgG1, IgG2a and IgG2b antibody response in sensitized mice given the low dose of Dp. In contrast, high doses of Dp stimulated IgG1 antibody production in both naive and sensitized animals. In addition, the oral tolerance induction protocol stimulated anti-F(ab')2gamma and anti-Fcgamma autoantibody production. Evaluation of IgG anti-IgE autoantibodies by a direct enzyme immunoassay (EIA) revealed the presence of these autoantibodies, predominantly of the IgG1 isotype, specifically in those animals fed with the high dose. In contrast, IgG-IgE complexes, determined by EIA using immobilized anti-IgE antibodies, were detected mainly in sera of control animals. The autoantibody anti-IgE specificity was tested against IgE-TNP and IgE-DANSYL murine proteins and revealed different inhibition profiles, suggesting the action of heterogeneous subpopulations of autoantibodies. Taken together, our results show that the oral tolerance protocol with Dp was able to modulate the production of allergen-specific IgE antibodies in both naive and sensitized animals. In addition, we suggest that anti-IgE autoantibodies participate in the modulation of allergic response triggered by oral tolerance protocols.

SUMMARYOne of the main goals of immunotherapy of allergic diseases is the down-regulation of the type I hypersensitivity reaction. We investigated in this study the effect of oral administration of varying doses (0·25, 1·0, 4·0 and 10 mg) of dust mite extract (Dermatophagoides pteronyssinus, Dp) in sensitized A/Sn mice. A marked decrease of the allergen-specific immunoglobulin E (IgE) response was observed with all antigen doses. The mice orally tolerized with low Dp dose (0·25 mg) had a significant decrease in the total serum IgE and in the immunoglobulin G1 (IgG1), IgG2a and IgG2b antibody levels. The higher Dp dose (10·0 mg), however, enhanced the IgG1 antibody response, suggesting the stimulation of a pre-existing immune response of the sensitized animals. Animals fed with the low Dp dose had a significant decrease in the frequency of interleukin-4 (IL-4) secreting cells. These animals also showed a significant decrease in the frequency of Dp-specific IgE-and IgG1-positive plasma cells. Our data suggest that feeding dust mite extract to Dp-sensitized mice down-regulates the development of type I hypersensitivity, by inhibition of the T helper 2 response. INTRODUCTIONit is unclear how and whether these oral tolerance-induced IL-4-producing cells can modulate allergic responses that are In allergic processes, cytokines secreted by T helper 2 (Th2) themselves mediated by Th2 cells. cells, such as interleukin-4 (IL-4), play a pivotal role on the Oral tolerance protocol is usually studied in naive animals.1 onset and maintenance of immunoglobulin E (IgE) responses.The evaluation in previously immunized animals is of parThis observation is the rationale for treatments of allergic ticular interest to the development of immunotherapeutic response that are based on the down-regulation of Th2 cell approaches for human allergic diseases. However, these studies functions.must take into account that oral administration of antigen to One of the protocols used to induce antigen-specific sysimmunized animals might occasionally enhance a pre-existing temic immune tolerance is based on the oral antigen adminisimmune response.11-13 We have previously shown that the oral tration followed by a challenge with the same antigen.1 administration of Dp has a more pronounced inhibitory effect Suppression of Th1-mediated inflammatory responses by oral in sensitized mice than in naive mice.14 The induction of oral administration of autoantigen has been observed in several tolerance is a complex process that is influenced by many autoimmune disease and transplantation models.2,3 Among factors, such as animal age, genetic background and dose and the oral tolerance applications, there is a special interest in the administration regimen of the tolerogen.15 modulation of the Th2-allergic-mediated diseases,4-7 since Th1In the present work, we investigated the effect of oral and Th2 cells can be inactivated by feeding antigen.8 administration of varying doses of dust mite extract in a CD4 lymphocytes have an important role on the regulation mu...

Mother-pup interaction, as well as other behavioral reactions were studied during the lactation period in 24 litters of Wistar rats and their dams fed either a 16% (control -C; 12 litters) or a 6% (malnourished -M; 12 litters) protein diet. The diets were isocaloric. Throughout lactation there was a 36.4% weight loss of M dams and a 63% body weight deficit in the M pups when compared to control pups. During this period, half of the litters were exposed daily to additional tactile stimulation (CS or MS), while the other half were submitted to normal rearing conditions (CN or MN). The tactile stimulation of pups (handling) consisted of holding the animal in one hand and gently touching the dorsal part of the animals body with the fingers for 3 min. A special camera and a time-lapse video were used to record litter behavior in their home cages. Starting at 6 p.m. and ending at 6 a.m., on days 3, 6, 12, 15, 18 and 21 of lactation, photos were taken at 4-s intervals. An increase in the frequency (154.88 ± 16.19) and duration (455.86 ± 18.05 min) of suckling was observed throughout the lactation period in all groups compared to birth day (frequency 24.88 ± 2.37 and duration 376.76 ± 21.01 min), but the frequency was higher in the C (84.96 ± 8.52) than in the M group (43.13 ± 4.37); however, the M group (470.2 ± 11.87 min) spent more time suckling as compared with the C group (393.67 ± 13.09 min). The M dams showed a decreased frequency of resting position throughout the lactation period (6.5 ± 2.48) compared to birth day (25.42 ± 7.74). Pups from the C group were more frequently observed separated (73.02 ± 4.38) and interacting (258.99 ± 20.61) more with their mothers than the M pups (separated 66.94 ± 5.5 and interacting 165.72 ± 12.05). Tactile stimulation did not interact with diet condition, showing that the kind of stimulation used in the present study did not lead to recovery from the changes induced by protein malnutrition. The changes in mother-pup interaction produced by protein malnutrition of both may represent retardation in neuromotor development and a higher dependence of the pups on their mothers. These changes may represent an important means of energy saving and heat maintenance in malnourished pups.

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