Potentiation of IgE production to common environmental allergens by storage house dust mite Dermatophagoides farinae

The biological activity of serum IgE changes over the course of a primary response

Mast-cell degranulation is triggered by the bridging of Fc receptor-bound antigen-specific immunoglobulin IgE on the cell surface. In vitro experiments suggest that antibody affinity and nonspecific IgE may affect the mast-cell function, however, their importance in vivo is unclear. Investigations of the effects of these parameters on mast-cell sensitization were therefore carried out in a rat immunization model in which the IgE response is transient and peaks on days 10-15. Between these two timepoints, significant changes in the level of specific IgE were not observed, but the avidity of specific IgE increased (P < 0.05). Total serum IgE peaked on day 10 and slowly declined, with the relative proportion of specific to total IgE increasing from day 10-15 (P < 0.05). Despite similar levels of antigen-specific IgE, increasing avidity and an increased proportion of specific IgE between days 10 and 15, the biological activity of IgE in the serum peaks on day 10 and declines rapidly, dropping around seven-fold by day 15 (P < 0.001). Mechanisms that could explain this finding, such as differential expression of IgE isoforms and changes in the fine specificity of the IgE response, are discussed.

B cell mitogenic activity of house dust mite, Dermatophagoides farinae, antigens

The effect of mite antigens on murine and human lymphocytes was studied in vitro. Antigens prepared from Dermatophagoides farinae feces and bodies stimulated normal murine spleen cells to proliferate in a dose-dependent manner. The responder cells are B cells, because the response was reduced by the treatment of spleen cells with anti-immunoglobulin antibody and complement, but not with anti-Thy 1 antibody and complement. Furthermore, nylon column-purified T cells did not respond. The stimulation of B cells with mite antigens was not due to the contamination of lipopolysaccharide, a representative B cell mitogen, because C3H/HeJ spleen cells which are low responders to lipopolysaccharide could respond to mite antigens. These antigens induced not only proliferative response of murine B cells, but also immunoglobulin production. By gel-filtration column chromatography, the active fractions were eluted around the molecular weight of 150-155 kDa. Furthermore, mite antigens also stimulated human B cells to proliferate and to produce immunoglobulin. All these results suggest that mite antigens are a potent B cell mitogen and this activity might concern the induction of allergic reaction.

Relation between frequency of asthma and IgE antibody levels against Dermatophagoides farinae and total serum IgE levels in schoolchildren

The relation between the frequency of wheezing illness and IgE antibody levels against Dermatophagoides farinae (Df) and total IgE levels was examined in 457 randomly selected schoolchildren. From the response to the ATS-DLD-78-C respiratory symptoms questionnaire, 14 subjects (3.1%) were found to have asthma syndrome (recurrent episodes of attacks of shortness of breath with wheezing) and 17 subjects (3.7%), wheezing syndrome (only wheezing). The percentage of the asthma syndrome increased with increasing levels of Df-specific IgE, and there was an intimate correlation between the percentage of asthma syndrome and Df-specific IgE levels (r = 0.97; p less than 0.001), whereas such association was not found between the two (r = -0.19; p greater than 0.5). Similar relations were found between the frequencies of the specific syndromes and total IgE levels. There was a significant correlation between total IgE levels and Df-specific IgE levels in the total population (r = 0.7; p less than 0.001). These results suggest that allergic reaction greatly contributes to the development of asthma in children.