The goal of this dissertation was to determine the mechanism by which CD86 (B7-2) stimulation on a CD40 ligand (CD40L)/Interleukin-4 (IL-4)-activated B cell activates NF-κB and increases the level of IgG1. Therapeutic interventions aimed at either suppressing or enhancing antibody production via CD86 signaling would need to target the specific intermediates activated by CD86 upstream of NF-κB. Thus, the hypothesis tested in this dissertation is that stimulation of CD86 on a CD40L/IL-4-activated B cell activates a distinct signaling pathway within the B cell to increase the activation of NF-κB and the gene transcription mediated by the 3’-IgH enhancer. The present data are the first to show the CD86 signal transduction pathway in a B cell proximal to NF-κB activation and the regulation of gene activity. We show that CD86 stimulation on a CD40L/IL-4-activated B cell increased the activity of PI3K, as well as the phosphorylation state of PDK1, Akt, IKKαβ, PLCγ2, and PKCαβ, to increase gene activity mediated by NF-κB and the hs4 region of the 3’-IgH enhancer. The present data also show that addition of CD28/Ig to Wt, but not CD86- or CD19-deficient, B cells increased the level of phosphorylation of Lyn and CD19, as well as the amount of Lyn, Vav, and PI3K proteins that immunoprecipitated with CD19. In vivo, serum IgG1 levels following immunization with a T cell-dependent antigen were decreased in mice receiving Wt-T/CD86-deficient B cells when compared to mice receiving Wt-T/Wt-B cells. The decrease in serum IgG1 was associated with a decrease in the level of B cell-associated Oct-2 mRNA and protein, but a normal level of germline IgG1 mRNA and Th2 cell-dependent IL-4. The significance of this dissertation is that it is the first study to identify the mechanism by which CD86 induces an intracellular signaling pathway directly in the B cell. The knowledge gained from this work will not only provide a molecular mechanism by which CD86 stimulation regulates the level of an IgG1 response, but also identify potential molecular targets for therapeutic interventions to selectively regulate the level of an IgG1 response positively or negatively.
|School:||The Ohio State University|
|Department:||Integrated Biomedical Science|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Keywords:||B cell, Cd86, Cell signaling, Costimulation, Kinase|
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