FUNCTION OF C3B AND C3BI RECEPTORS ON U937 CELLS

这个项目是对特定受体的详细分析。 激活补体第三组分(C3b受体) 人巨噬细胞系U937的细胞。这个项目欠它的 对我们实验室最新进展的可行性，即放射性标记 C3131I被激活并以C3b的形式并入稳定的、可溶的聚集体中 IgG125I(A-Ig G)和Ig M 125I(A-Ig M)。最近，我们使用了这些 研究U937细胞表面Fc受体和C3b受体的探针。我们有 证实了U937细胞上存在C3b受体，并显示 C3b受体本身并不能调节配体的内吞作用 含有C3b。我们现建议把这些研究扩展至以下范围： 明确的目标。(1)测定C3b受体在U937上的功能 C3b可溶性配体结合和内吞作用中的细胞 分子。(2)以类似的方式阐明C3bi的功能 含C3bi的可溶性配体与U937细胞表面受体的结合 (3)确定C3b和C3bi受体的数量是否可以 Fc受体的情况是调制的，如果是的话，是否调制了 补体受体获得了介导内吞作用的能力。我们会 利用荧光标记的抗C3b、C3bi和Fc受体的单抗 抗体用于定量细胞表面表达、密度、细胞内 U937细胞上C3b、C3bi和Fc受体的池和迁移率 荧光激活细胞分类器(FACS)分析。功能界别 这些受体各自的特性及其相互作用 其他的将通过U937细胞与C3b和C3bi二聚体反应来确定， 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培养细胞和 可溶性配体和抗受体抗体及流式细胞仪分析。这些 实验将使用用电势调节器处理的细胞重复进行 Fc、C3b和C3bi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C3b和C3bi受体的功能及其不同类型 的受体可以与“正协同作用”相互作用。最终这就是 信息可能有助于更好地理解免疫复合体如何 逃避正常的防御机制，并在组织中沉积，从而导致 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.