FUNCTION OF C3B AND C3BI RECEPTORS ON U937 CELLS

该项目是一个专门的受体的详细分析， 激活补体的第三成分（C3 b受体）， 人巨噬细胞系U937的细胞。 该项目欠其 我们实验室的最新进展的可行性， C3131 I被活化并作为C3 b掺入稳定的可溶性聚集体中 IgG 125 I（A-IgG）和IgM 125 I（A-IgM）。 最近，我们使用这些 研究U937细胞上的Fc受体和C3 b受体的探针。 我们有 证明了U937细胞上存在C3 b受体，并显示 C3 b受体本身不介导配体的内吞作用， 含C3 b。 我们现建议扩展这些研究，包括 具体目标。 (1)确定U937上C3 b受体的功能 细胞在携带C3 b的可溶性配体的结合和内吞中的作用 分子。 (2)以类似的方式阐明C3 bi的功能 U937细胞上的C3 bi受体在携带C3 bi的可溶性配体的结合中的作用。 (3)为了确定C3 b和C3 bi受体的数量是否可以被 如Fc受体的情况那样被调节，并且如果是这样，则调节的 补体受体获得介导内吞作用的能力。 我们将 利用荧光染料标记的单克隆抗C3 b、C3 bi和Fc受体 抗体来定量表面表达、密度、细胞内 U937细胞上C3 b、C3 bi和Fc受体的库和迁移率， 荧光激活细胞分选仪（FACS）分析。 功能 这些受体的特性分别和相互作用， 另一种是通过使U937细胞与C3 b和C3 bi二聚体反应来测定， AlgM.C3b、AlgM.C3bi和AlgG.C3bi。 这些受体的作用机制 相互作用将通过同时孵育细胞与 可溶性配体和抗受体抗体和FACS分析。 这些 将使用用潜在调节剂处理的细胞重复实验 Fc和C3 b和C3 bi受体的数量和功能，并与 未经处理的细胞 这些研究应该会揭示重要的新信息 关于C3 b和C3 bi受体的功能以及不同类型的受体 受体之间的相互作用具有“正协同性”。“最终， 这些信息可能有助于更好地理解免疫复合物如何 逃避正常的防御机制，并在组织中存款， 肾小球肾炎、类风湿性关节炎和血管炎等疾病。

This project is a detailed analysis of specialized receptors for the activated third component of complement (C3b receptors) on the surface of cells of the human macrophage cell line U937. The project owes its feasibility to a recent advance in our laboratory whereby radiolabeled C3131I is activated and incorporated as C3b into stable, soluble aggregates of IgG125I (A-IgG) and IgM125I (A-IgM). More recently, we have used these probes to study Fc receptors and C3b receptors on U937 cells. We have demonstrated the presence of C3b receptors on U937 cells and have shown that C3b receptors alone, do not mediate the endocytosis of ligands containing C3b. We now propose to extend these studies with the following specific aims. (1) To determine the function of C3b receptors on U937 cells in the binding and endocytosis of soluble ligands bearing C3b molecules. (2) To elucidate in a similar fashion the function of C3bi receptors on U937 cells in the binding of soluble ligands bearing C3bi. (3) To determine whether the number of C3b and C3bi receptors can be modulated as is the case for Fc receptors, and if so, whether the modulated complement receptors gain the ability to mediate endocytosis. We will utilize fluorochrome labeled monoclonal anti C3b, C3bi, and Fc receptor antibodies to quantitate the surface expression, density, intracellular pool and mobility of the C3b, C3bi and Fc receptors on U937 cells, by fluorescence activated cell sorter (FACS) analysis. The functional characteristics of these receptors separately and in interaction with each other would be determined by reacting U937 cells with C3b and C3bi dimers, AlgM.C3b, AlgM.C3bi, and AlgG.C3bi. The mechanisms of these receptor interactions would be studied by simultaneous incubation of cells with soluble ligands and anti receptor antibodies and FACS analysis. These experiments would be repeated using cells treated with potential modulators of Fc and C3b and C3bi receptor number and function, and compared with untreated cells. These studies should reveal important new information concerning the function of C3b and C3bi receptors and how different types of receptors can interact with "positive cooperativity." Ultimately this information may lead to a better understanding of how immune complexes may escape normal defense mechanisms and deposit in tissues to cause such diseases as glomerulonephritis, rheumatoid arthritis and vasculitis.