Low dose of orally administered antigen down-regulates the T helper type 2-response in a murine model of dust mite hypersensitivity

One of the main goals of immunotherapy of allergic diseases is the down-reg ulation of the type I hypersensitivity reaction. We investigated in this st udy 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 sensiti zed A/Sn mice. A marked decrease of the allergen-specific immunoglobulin E (IgE) response was observed with all antigen doses. The mice orally toleriz ed 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 sensit ized animals. Animals fed with the low Dp dose had a significant decrease i n the frequency of interleukin-4 (IL-4! secreting cells. These animals also showed a significant decrease in the frequency of Dp-specific IgE- and IgG 1-positive plasma cells. Our data suggest that feeding dust mite extract to Dp-sensitized mice down-regulates the development of type I hypersensitivi ty, by inhibition of the T helper 2 response.