title: New insights into the mechanisms which regulate IgE synthesis in man.
abstract: The studies summarized here provide further insight into the cellular and molecular mechanisms involved in the regulation of human IgE synthesis. They clearly demonstrate that IL-4 is the essential factor for induction of human IgE synthesis, since no substantial in vitro IgE production can be obtained in the absence of this lymphokine. Another T cell-derived lymphokine, IFN-gamma, negatively regulates the IgE synthesis induced by IL-4. These two lymphokines can be produced by different T helper cells, but they can also represent the product of the same T cell clone (TCC). In this case, the possibility that a given TCC provides helper function for IgE seems to be dependent upon the balance between the amounts of the two lymphokines produced. Additional cellular and/or molecular signals are involved in IL-4-dependent IgE synthesis. First of all, a direct T-B interaction is required to precede the activity of IL-4. This interaction does not necessarily consist of cognate interaction between T and B cells, as occurs for IgE synthesis induced by alloreactive TCC. In the presence of exogenous IL-4 virtually all CD4+, and even a number of CD8+, TCC can provide the signaling required by B cells to synthesize IgE. An interaction between some adhesion molecule, more expressed on activated than resting T cells, and its receptor on B cells is sufficient to prepare resting B cells to synthesize IgE in response to IL-4. Furthermore, T cells also contribute to IL-4-dependent IgE synthesis by releasing IL-2.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.forename: S
authors.initials: S
authors.lastname: Romagnani
authors.forename: G
authors.initials: G
authors.lastname: Del Prete
authors.forename: E
authors.initials: E
authors.lastname: Maggi
authors.forename: P
authors.initials: P
authors.lastname: Parronchi
authors.forename: M
authors.initials: M
authors.lastname: Ricci
mesh_terms: D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D007073:Immunoglobulin E