The overall goal of this research project is to understand the mechanism by which norepinephrine (NE) and beta-2-adrenergic receptor (a2AR) stimulation regulate the Th2 cell-dependent antibody response. With the reality of bioterrorism, the need to elucidate the molecular and biochemical mechanisms by which the release of antigen- and stress-induced NE affects immune responsiveness is critical. Our laboratory has reported that NE stimulates the a2AR on a B cell to increase the level of IgG1 produced per cell, and that stimulation of CD86 (B7-2) increases this level further. Although the mechanisms by which CD40 and IL-4 receptor signaling affect IgG1 production are known, little is known about those induced by the a2AR and CD86. Preliminary data show that the level of mature IgG1 transcript, IgG1 protein, and nuclear protein binding to the 3'-IgH enhancer region of the IgH locus increase following a2AR and/or CD86 stimulation on a CD40L/IL-4-activated B cell, but that mature IgG1 transcript stability and IgG1 class switching are unaffected. Importantly, this finding dissociates the a2AR- and CD86-induced effect on the expression of the rearranged IgG1 gene from an effect on IgG1 class switching. Unlike the a2AR-activated signaling pathway, the CD86-activated signaling pathway remains unknown. We propose to test the hypothesis that a2AR and/or CD86 stimulation on a B cell increase the rate of mature IgG1 transcription through signaling intermediates that regulate 3'-IgH enhancer activity. The following specific aims are designed to test this hypothesis in vitro and in vivo by using B cells from wild type and a2AR- or CD86-deficient mice. We will determine if stimulating these receptors 1) Increases either IgG1 class switching and/or the rate of mature IgG1 transcription using real-time PCR and nuclear run-on analysis; 2) Increases the level of a DNA-binding protein at the 3'-IgH enhancer using EMSA, super shift, chromatin immunoprecipitation (CHIP), and a transient transfection gene reporter system; and 3) Increases the activation of a specific signaling pathway(s) using selective inhibitors for PKA, PKC, and MAPK. The significance of testing our hypothesis is that the findings will provide a molecular basis for the role of NE, a2AR, and CD86 stimulation in regulating the Th2 cell-dependent Ab response, thus providing a defined target for therapeutics and a potential mechanism for increasing the efficacy of vaccination protocols.
