[Regulation and dysregulations of immunoglobulin E synthesis]

Compared to other isotypes of immunoglobulins, IgE antibodies are present in exceedingly low concentrations in normal serum, because their synthesis is maintained under the strict control of several intricate regulatory mechanisms. These normally unapparent mechanisms become accessible to investigations in a number of pathological dysregulations. One may distinguish three orders of controls. An elementary isotypic circuit, constructed on the interactions between IgE Fc portions and IgE-binding molecules, directly regulates IgE synthesis by IgE-secreting B cells. IgE-binding molecules are themselves controlled by several lymphokine cascades, depending on external and genetic factors. The functioning of the IgE isotypic circuit is coordinated with other circuits, corresponding to other immunoglobulin isotypes, by means of an isotypic network, connected to other homeostatic systems of the organism. The dissection of these regulatory mechanisms and an understanding of their interactions are potentially useful for new therapeutic approaches.