IgG subclass and function of anti-polysaccharide abs

描述（由申请方提供）：抗多糖（PS）抗体（Ab）对于宿主防御包囊细菌至关重要。抗PS Ab的功能包括补体固定和细菌的调理作用以通过吞噬细胞杀伤，以及通过与Fc γ受体（Fc γ R）结合来调节细胞因子产生细胞。 IgG抗PS Ab应答延迟了个体发育和同种型限制（小鼠中的IgG 3，人中的IgG 2），PS与蛋白质的偶联诱导向IgG 1的类别转换。确定同种型限制和IgG亚类对抗PS Ab功能的影响对于更好地理解对PS包封细菌的免疫力、人IgG亚类缺陷的发病机制以及改善PS和PS缀合物疫苗免疫力的血清学相关性至关重要。在本提案中，我们将继续研究IgG亚类在抗PS Ab效应子功能中的作用，确定恒定区基因和优势IgG亚类在对包囊细菌的免疫中以及在PS与蛋白质缀合时发生的类别转换中的作用，并研究IgG亚类对Fc γ R介导的细胞因子产生调节的影响。我们将利用针对铜绿假单胞菌LPS O-侧链和S. pneumoniae（Pn）荚膜PS中制备的一种新的转基因小鼠与人IG基因重组，以确定Ab保护功效的功能差异的机制。接下来，为了确定对PS产生的主要IgG亚类的体内相关性，我们将使用新的BALB/c IgG 3敲除小鼠来确定抗PS Ab亚类在宿主对PS、PS-蛋白缀合物和对包囊细菌感染的应答中的重要性。我们已经发现，IgG 3的情况下，使这些动物更容易受到致命的感染与Pn，但诱导抗PS IgG 1可以纠正这一缺陷。最后，我们将研究FcR介导的IgG亚类在巨噬细胞产生细胞因子中的调节作用，我们假设IgG亚类基于与FcgammaR的差异结合来调节细胞因子产生的能力存在差异。这些研究将允许针对细菌的主动和被动免疫的更合理的策略，提高对IgG亚类缺陷的理解，以及关于哪个IgG亚类具有最佳Fc γ R介导的抗炎特性的新信息。

DESCRIPTION (provided by applicant): Anti-polysaccharide (PS) antibodies (Ab) are critical to host defense against encapsulated bacteria. The function of anti-PS Ab includes complement fixation and opsonization of bacteria for killing by phagocytes, and modulation of cytokine producing cells via binding to Fcgamma receptors (FcgammaR). IgG anti-PS Ab response has delayed ontogeny and isotype restriction (IgG3 in mice IgG2 in man), and conjugation of PS to proteins induces class switching to IgG1. Determining the effect of isotype restriction and IgG subclass on function of anti-PS Ab is crucial to better understand immunity to PS-encapsulated bacteria, the pathogenesis of human IgG subclass deficiency and for improved serological correlates of immunity with PS and PS conjugate vaccines. In this proposal, we will continue our studies of the role of IgG subclass in anti-PS Ab effector function, determine the role of constant region genes and the dominant IgG subclass in immunity to encapsulated bacteria and in class switching that occurs when PS are conjugated to proteins, and investigate the effect of lgG subclass on FcyR mediated regulation of cytokine production. We will utilize V region-identical human monoclonal Abs of all four IgG subclasses against P. aeruginosa LPS O-side chain and S. pneumoniae (Pn) capsular PS made in a new transgenic mouse reconstituted with human Ig genes, to determine the mechanism of functional differences in Ab protective efficacy. Next, to determine the in vivo relevance of the dominant IgG subclass made to PS, we will use the new BALB/c IgG3 knockout mouse to determine the importance of anti-PS Ab subclass in the host response to PS, PS-protein conjugates and to infection with encapsulated bacteria. We have found that the absence of IgG3 renders these animals more susceptible to fatal infection with Pn but that induction of anti-PS IgG1 can correct this defect. Finally, we will investigate the FcR mediated regulatory role of IgG subclass in cytokine production by macrophages, and we hypothesize that there are differences in the ability of IgG subclass to modulate cytokine production based on differential binding to FcgammaR. These studies will allow more rational strategies of active and passive immunization against bacteria, improved understanding of IgG subclass deficiency, and new information about which IgG subclass has the best FcgammaR-mediated anti-inflammatory properties.