IgG subclass and function of anti-polysaccharide abs

描述(由申请人提供)：抗多糖(PS)抗体(Ab)对宿主防御被包裹的细菌至关重要。抗PS抗体的功能包括结合补体和调理细菌以供吞噬细胞杀伤，以及通过与FcGamma受体(FcGammaR)结合调节细胞因子产生细胞。Ig G抗PS的抗体反应具有延迟的个体发育和同型限制(小鼠的IgG3和人的IgG2)，PS与蛋白质的结合诱导类向IgG1的转换。确定同型限制和Ig G亚类对抗PS-Ab功能的影响，对于更好地了解对PS包膜细菌的免疫、人Ig G亚类缺陷的发病机制以及改进PS和PS结合疫苗免疫的血清学相关性是至关重要的。在这项研究中，我们将继续研究免疫球蛋白G亚类在抗PS抗体效应器功能中的作用，确定恒定区基因和主要的免疫球蛋白G亚类在对包裹细菌的免疫以及PS与蛋白质结合时发生的类转换中的作用，并探讨LGG亚类在FcyR介导的细胞因子产生调节中的作用。我们将利用四种免疫球蛋白亚类的V区相同的人抗铜绿假单胞菌LPSO侧链和肺炎链球菌(PN)囊膜PS的单抗，在一个新的重组人Ig基因的转基因小鼠中制备，以确定功能差异在抗体保护效果中的机制。接下来，为了确定主要的免疫球蛋白亚类与PS的体内相关性，我们将使用新的BALB/c IgG3基因敲除小鼠来确定抗PS抗体亚类在PS、PS蛋白结合物和微囊化细菌感染的宿主反应中的重要性。我们发现，缺乏IgG3使这些动物更容易受到致命的PN感染，但诱导抗PS IgG1可以纠正这一缺陷。最后，我们将研究FCR介导的免疫球蛋白亚类在巨噬细胞产生细胞因子中的调节作用，我们假设基于与FcGammaR的不同结合，免疫球蛋白亚类调节细胞因子产生的能力存在差异。这些研究将使针对细菌的主动免疫和被动免疫的策略更加合理，提高对免疫球蛋白亚类缺陷的了解，以及关于哪种免疫球蛋白亚类具有最好的FcGammaR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.