1997 — 1999 |
Lynes, Michael A [⬀] |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Mechanism of Metal Mediated Immunosuppression @ University of Connecticut Storrs
DESCRIPTION: (Adapted from the Investigator's Abstract) Heavy metals (such as Cd, Hg, Ni, Zn, Cu, and Pb) are increasingly important contaminants of air, water, and soils. One of the critical biological systems which can be altered by exposure to heavy metals is the immune system, where inappropriate changes in immune capacity can result in immunodeficiency or autoimmune disease. While there is a great deal of interest in the mechanisms by which heavy metals alter immunity, there remain many unresolved issues. In preliminary studies, the investigators have examined the contributions that MT (a small, cysteine-rich metalloprotein that is rapidly induced in cells following heavy metal exposure) might make to altered immune activity. Metallothionein may be responsible for some of the forms of humoral immunosuppression associated with metal exposure. For example, the investigators have found that MT suppresses specific T-dependent humoral responses, and that some aspects of macrophage function are altered by MT. They have also found that monoclonal antibodies to MT developed in our laboratory can block some in vivo immunomodulatory activities of MT. The investigator's findings suggest that MT induced by heavy metal exposure (or indeed by exposure to other toxicants) is responsible for decreases in immunity as a consequence of antigen-presenting cell/helper T-cell interactions. The central parameters of the humoral response that are potential targets of the suppressive effect of MT will be evaluated. These experiments will establish the mechanisms by which suppressive effects occur. The Specific Aims are to: (1) explore the dynamics of in vivo MT interactions with the immune system and to determine if suppression of humoral immunity is found in both T-dependent and -independent responses, (2) to examine the effects of MT on the role that T-lymphocytes play in regulation of the humoral immune response, (3) to determine whether the interactions of helper T-cells and macrophages are altered by MT, and (4) to establish whether patterns of B-cell differentiation are altered by the presence of MT. This research will have important implications both for the identification of individuals at particular risk for immune disease as a consequence of heavy metal exposure, and for the diagnosis and treatment of individuals exposed to excessive levels of these important environmental toxins.
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2003 — 2007 |
Lynes, Michael A [⬀] |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
A Mechanism of Metal-Mediated Immunosuppression @ University of Connecticut Storrs
DESCRIPTION (provided by applicant): Heavy metal cations such as cadmium are widely found in the environment and can act as potent immunosuppressive agents. One of the biological responses to many immunosuppressive toxicants is the production of stress response proteins. Metallothionein (MT) is an intriguing example of this group of proteins, and plays several critical roles in cellular homeostasis. MT acts as a reservoir of essential metals, as a potent anti-oxidant, as a protein that can sequester toxic heavy metals and as a regulator of several transcription factors. These functions implicate MT in metal-mediated immunomodulation. We have shown that MT can significantly influence immune functions in vivo and in vitro. The fundamental premise of this proposal is that a functional immune response exists in the context of an optimum level of MT. When MT levels are elevated beyond this optimal range by toxicant exposure, we predict that significant declines in immune function will occur. We plan to evaluate these hypotheses by using two recently derived mouse strains that are both congenic with C57BL/6J. The transgenic MT strain has multiple Mt1 genes that drive MT overexpression, and the second carries targeted disruptions of the Mt1 and Mt2 genes. Our specific aims are:(1) to test the hypothesis that manipulations of metallothionein gene dose will alter the immunosuppressive consequences of exposure to cadmium, (2) to test the hypothesis that metallothionein overproduction will decrease the available oxidant in leukocytes and diminish oxidant-related damage to leukocyte plasma membranes in cells harvested from animals exposed to immunosuppressive doses of cadmium, (3) to test the hypothesis that toxicant-induced metallothionein will alter the sub-cellular distribution and tissue distribution of essential and toxic metals to immune organs and cells in the cadmium-exposed animal, and (4) to test the hypothesis that metallothionein gene dose in an animal will influence the signal transduction cascade and specific transcription factor activities in cadmium-exposed animals. This research will broaden our understanding of the pathogenic mechanisms by which environmental agents act to elicit disease, should contribute to our understanding of individuals that are especially sensitive to toxicant immunomodulation, and may suggest new avenues of therapeutic benefit in Cd and other toxicant-exposed patients.
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