Characterization and signal transduction pathways of a novel human B cell differentiation factor.
Item
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Title
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Characterization and signal transduction pathways of a novel human B cell differentiation factor.
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Identifier
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AAI9510672
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identifier
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9510672
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Creator
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Huang, Ruoqing.
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Contributor
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Adviser: Lloyd Mayer
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular | Health Sciences, Immunology
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Abstract
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We have recently identified a novel human B cell differentiation factor, 446-BCDF derived from anti-CD3 stimulated peripheral blood (PB) T cells. This novel cytokine induces a more than 5 fold increase in immunoglobulin secretion by both SAC activated PB B cells and tonsil B cells. 446-BCDF has been partially purified and has an apparent molecular weight of 32 Kd and a pI of 6 which are distinct from the molecular weight of IL2, IL4, IL10, IL13, and the pI of IL6. Bioassays show that this partially purified 446-BCDF does not contain detectable IL2, IL4, and IL6 activity and 446-BCDF activity can not be blocked by antibodies against these cytokines or their receptors. 446-BCDF induces IgM, IgG, IgA but no IgE secretion, and can be specifically inhibited by a monoclonal antibody 929. With this partially purified cytokine, we initiated studies to investigate signaling pathways involved in 446-BCDF mediated B cell differentiation. A cAMP analogue (Dibutyryl cAMP), an adenylate cyclase stimulator (forskolin), and phosphodiesterase inhibitors (aminophylline and IBMX) all inhibited Ig secretion induced by 446-BCDF. Direct measurement of cAMP levels demonstrated that 446-BCDF induced a reduction of intracellular cAMP in a time dependent manner. This reduction may be due to the stimulation of adenylate cyclase via a Gi linked receptor since a potent Gi protein inhibitor, pertussis toxin, was able to prevent the 446-BCDF induced decrease in intracellular cAMP and inhibit Ig secretion. Angiotensin II (AT II) also induced a reduction in intracellular cAMP via a Gi linked receptor and stimulated Ig secretion by SAC activated B cells. Ig secretion induced by AT II was significantly enhanced by 446-BCDF, suggesting that in addition to inducing a decrease in intracellular cAMP 446-BCDF may also deliver other signals to induce Ig secretion. This hypothesis was supported by the observation that 446-BCDF stimulated B cells to produce IP{dollar}\sb3{dollar} and flux Ca{dollar}\sp{lcub}++{rcub}{dollar}. The latter event was critical to Ig secretion since a calcium chelator, BAPTA, was able to block Ca{dollar}\sp{lcub}++{rcub}{dollar} flux and Ig secretion induced by 446-BCDF without affecting cell viability. PKC activity was not detected using a specific PKC assay system. 446-BCDF activity was not inhibited by PKC and serine/threonine kinase inhibitors. However, 446-BCDF activity was inhibited by a tyrosine kinase inhibitor, genistein. Taken together, these data suggest that the reduction in intracellular cAMP may an important signal to trigger human B cell Ig secretion which is a Ca{dollar}\sp{lcub}++{rcub}{dollar} dependent event. Tyrosine kinase may also play a role in B cell differentiation.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
