The zinc deficient mouse (ZD) is a valuable model for elucidating the molecular and biochemical changes made by the immune system to provide a core of host defense in the face of suboptimal nutriture. Accelerated apoptosis disrupts lymphopoiesis creating lymphopenia, but splenic lymphocytes of the ZD mouse have greater potency. Conversely, myelopoietic cells that provide innate immunity remain intact maintaining zinc homeostasis. The studies below represent the first experiments to explore in depth the effect of suboptimal nutriture on hematopoietic processes. 1. Lymphopoiesis: The role of apoptosis in disrupting lymphopoiesis will be further defined in vivo using a transgenic mouse over-expressing the anti-apoptotic protein Bcl-2 in cells of the B-lineage allowing us to compare the survival of protected pre B cells versus unprotected pre T cells during ZD. Pro B cells which accumulated in ZD mice will be examined for expression of Pax 5, a transcription factor key to B cell development. We suspect it is low in pro B cells from ZD mice allowing them to engage in lineage reversal joining the ever increasing pool of myeloid cells. We also suspect phenotypic analysis of progenitor cells in ZD mice will show they are also skewed towards myelopoiesis. 2. Myelopoiesis: The rate of production of monocytic and granulocytic cells in ZD mouse will be ascertained to see if the rates are actually accelerated as data suggests. Experiments are proposed to determine the intrinsic zinc content of these cells and the role of zinc transporters in enabling them to differentiate and proliferate in a zinc depleted environment. Changes in gene expression especially the glucocorticoid receptor (GcR) will be evaluated to better understand how these cells survive in a low zinc environment that includes elevated glucocorticoids (Gc). Objective 3. Evaluate the Impact of Low Zinc (LZ) versus Gc on Myelopoiesis. One cannot decipher the impact of LZ versus accompanying Gc on cells in vivo. Therefore, a LZ culture has been developed to which Gc can be added to decipher the effects of each alone and in combination on these aspects of myelopoiesis (a) effects on maturation - proliferation, (b) effects on function to include the oxygen burst and phagocytosis, (c) effects on expression of GcR (data indicate myeloid cells survive Gc-induced apoptosis by down regulating GcR), (d) cDNA microarray analysis of changes in expression of 200 genes involved in cell survival and apoptosis. Objective 4. Adaptation Strateqies of Splenic Lymphocytes. Naive T and B cells from ZD mice will be examined for enhanced expression of la, IgM, BCR, TCR, CD3, IL-2R, CD40 and CD40L, etc., which could account for their heightened responses. The basal rate of apoptosis, ability to withstand an active apoptotic challenge, potency of response to antigenic challenges will be evaluated to see if splenic T and B cells of the ZD mouse have developed adaptations to their harsh environment.
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