Regulation of human IgE response by T cells and their products.

An in vitro experimental system for the induction of human IgE production has been established with human peripheral blood lymphocytes (PBL). For the assessment of IgE produced in vitro, a sensitive ELISA method has been developed by employing monoclonal anti-IgE antibodies. The stimulation of PBL with pokeweed mitogen plus Staphylococcus aureus strain Cowan I induced polyclonal IgE response. T cells from patients with pulmonary tuberculosis, after activation with purified protein derivative and/or IgE, suppressed selectively IgE response, and the suppressive activity was found to be mediated by IgE-specific suppressor factor with affinity for IgE molecules. The suppressive activity was effective both on spontaneous IgE production as well as on mitogen- or antigen-induced IgE response in the PBL culture from atopic patients. The affinity of the suppressor factor for IgE was suggested to be due to the structural similarity with Fc epsilon R on B cells. Absorption experiment suggest that the factor may bear class II major histocompatibility complex (MHC) molecules, although its effect was not MHC-restricted.