Our laboratory has identified IgE-dependent histamine releasing factors (HRF) from a variety of sources including nasal lavages from unstimulated individuals, nasal lavages obtained during the late phase of IgE-dependent reactions (LPR), blister fluids during LRP, and human lung macrophage supernatants. Our working hypothesis is that these IgE-dependent HRF are responsible for stimulation of basophils and/or mast cells during LPR. We obtained large quantities of nasal lavages from unstimulated individuals and partially purified and characterized HRF. Only certain donors' basophil respond to these HRF. Preliminary results show that passive sensitization of acid-treated basophils (to remove surface IgE) with responders sera restores HRF-induced release, but-sensitization with non-responders' sera (having the same concentration of IgE) does not. Both passive sensitized preparations respond equally to anti-IgE. The ability to restore responsiveness to HRF is dependent on IgE: it is ablated by heat treating serum, by absorbing serum on anti-IgE Sepharose, and by mixing serum with excess IgE myeloma. These data suggest that IgE molecules are functionally heterogeneous, in that only those from responders interact with HRF. We will further characterize this nasal lavage HRF via biological and physicochemical investigations. This will be accomplished with studies of cross desensitization between several HRF, anti-IgE and f-met-peptide. We will determine the spectrum of mediators released from basophils and mast cells by HRF. Purification will be extended from ion-exchange and Sephadex chromatography to isoelectric focusing, polyacrylamide and SDS gel electrophoresis. With preparations of high purity we will make a monospecific antibody to the nasal HRF and use it to test similarities/differences between the factors from various sources, and to isolate large quantities of HRF. We will seek to understand the nature of the functional IgE heterogeneity, first by isolating IgE from responders' and non-responders' serum and confirming, with passive sensitization experiments, that it is interaction with responder IgE that is responsible for activity of HRF. Second, we will use IgE from responders to make affinity columns to purify HRF. Third, we will attempt to determine where HRF interacts with IgE: i.e. Fab, Fc, carbohydrate. Finally we will further characterize HRF in other chronic inflammatory states, such as cultured synovial cells, and will determine which subsets of individuals are capable of producing HRF.
| MacDonald, S M; White, J M; Kagey-Sobotka, A et al. (1991) The heterogeneity of human IgE exemplified by the passive transfer of D2O sensitivity. Clin Exp Allergy 21:133-8 |
