Induction and measurement of IgE : a study in mice, with emphasis on the regulatory role of lymphokines

A better understanding of the regulatory mechanisms and cellular interactions of the IgE antibody response is of fundamental interest to allergologists and clinical immunologists because of the role of IgE in the pathogenesis of the immediate type allergic disease. In addition, basic knowledge of the regulation of IgE antibody formation may lead to new forms of treatment including suppression of excessively formed IgE antibody. Beyond the clinical significance, the IgE antibody response provides an excellent model to establish the interdependencies and regulatory events governing the expression of different isotypes at different levels. The formation of IgE antibodies is regulated by T cells and controlled by antigen- and/or isotype-specific interactions. Thus, external modulation of IgE production can be achieved by antigen, idiotype and anti-idiotype, being specific recognition elements in the establishment and control of an immune response. Also IgE specific regulatory factors and receptors on different types of cells exert a regulatory influence. In the case of isotype-specific regulation, total IgE antibody may be affected irrespective of its specificity. This is of relevance for eventual treatment of generalized IgE mediated allergic diseases. On the other hand, an antigen-specific modulation of an immune response will also affect the expression of other isotypes, even in a secondary response. From the above it is clear that much of the knowledge on the induction of the allergic inflammation gained from animal studies is clinically relevant. Moreover, the basic mechanisms of IgE regulation seem to be similar in man and in mice and rats. This is the underlying premise for these studies. The purpose of the investigations presented in this thesis was to get more insight into the mechanisms underlying the induction of IgE antibody formation in the mouse and the regulation of this IgE synthesis. For this study the development of suitable reagents and appropriate assay systems was indicated. Only since the availability of antigen-specific mouse IgE-secreting hybridomas, it became feasible to isolate enough IgE for the induction of heterologous anti-IgE antisera. This purified IgE can also be used as a reference standard in the quantitative determination of IgE. Furthermore, the hybridoma cells can be employed for the standardization of techniques that allow the determination of IgE-secreting cells. It is therefore that in Chapter 4 we focuss on the isolation and purification of monoclonal murine IgE, the generation of heterologous IgE-specific antisera and the development of a Terasaki-ELISA system for the quantitative determination of secreted IgE. Employing one of these antisera, we devised techniques for the determination of both total and antigen-specific IgE-secreting cells. Moreover, in this chapter, some critical factors influencing the applicability of these reagents and techniques are discussed.