The mechanisms by which lead (Pb) alters immune reactivities are multifactorial, both MHC and non-MHC genes are likely involved, in that there appear to be independent effects on T cells, B cells and macrophages, and these effects appear to involve different cytokines and signaling/transcription factors. The long-term goal of this project is to determine the sub cellular mechanisms by which Pb alters lymphocyte development (naive to memory cells) and the activation and reactivity of memory T cells which could influence immunity causing hypo- or hyper-responsiveness. This proposal tests the hypothesis that the heavy metal Pb can alter immune status by biochemical and molecular modulations resulting in a preferential environment for development of type-2 responses, and dependent on the particular type of immune response needed for defense against an infectious agent, cancer or regulation of self-reactive response, this """"""""skewing"""""""" may increase pathologies associated with lessened type-] and enhanced lype-2 immune responses. Synergies between chemical, physical and/or emotional stresses can enhance the skewing of immune reactivities toward type-] or type-2 responses; short-term imbalance is needed for appropriate defenses, but long-term imbalance exacerbates pathologies. Thus, an environmental agent such as Pb may alter the balance enough to increase morbidity. Mutant (genetic over-expressing or deficient) H-2d mice will be employed to assess the involvement of specific genes in the """"""""skewing"""""""" phenomenon. Specific questions to be addressed are: how Pb alters kinetic production of IFN?gamma; how macrophage reactivities, such as production of ILl 0, ILl 2 or ILl 8, are altered, and whether cellular thiol modifications are involved; whether Pb """"""""skewing"""""""" can be achieved with T cells specific only to OVA or whether T cells with self-reactivity (or metal-related specificities) are needed, whether B cells or a particular type of T cell subset (e.g., NK-like T cells) are required and within what particular cytokine environment; what molecular mechanisms are involved with the IL-4 reactivities of T cells; and what cells are responsible for the type-2 environment induced by Pb. Cell types will be assayed by flow cytometry and immunofluorescence microscopy. The presence of cytokines and signaling factors will be assessed by ELISA, microarray analysis (or RNAse protection) and western analyses. Pb heads the ATSDR list of toxic substances and its potential to induce or modify incidence of diseases associated with immune reactivities needs to be better understood. This cellular and molecular approach should identify the mechanisms by which Pb is immunomodulatory and assist evaluation of its health hazard and the molecular basis for the risks in exposure.
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