Human complement protein C1q forms together with C1r and C1s the C1 macromolecule, the first component of the classical complement pathway. Interaction of immune complexes with C1q induces a conformational change within the C1 complex, which results in activation of the classical pathway. C1q functions as recognition unit by binding to the heavy chain of IgG or IgM (Fc gamma and Fc micro) provided that the immunoglobulins are bound to their antigen. Furthermore, C1q can bind to apoptotic blebs, where it activates the classical complement pathway and mediates phagocytosis. As such, C1q promotes the clearance of apoptotic cells and subsequent exposure of auto antigens, thereby preventing stimulation of the immune system.
C1q is predominantly produced by macrophages but also by follicular dendritic cells, interdigitating cells and cells of the monocyte-macrophage lineage. C1q deficiency has a profound effect on host defence and clearance of immune complexes. Absence of C1q may cause autoimmunity by impairment of the clearance of apoptotic cells. Inherited C1q deficiency is also associated with the development of systemic lupus erythematosus (SLE).
C1q蛋白家族由众多含C1q结构域的蛋白组成, 从细菌到高等哺乳动物中都有分布。这类蛋白由一条信号肽、胶原样区(Collage-like region, CLR)和C1q球状结构域(Globular C1q domain, gC1q)组成。C1q蛋白家族根据其结构特点, 可分为三大类分子：C1q、C1q-like和ghC1q。C1q是补体经典途径的起始分子, 能够识别免疫复合物, 启动补体系统经典途径; 此外, 作为一种模式识别受体分子(Pattern recognition receptor, PRR), 它可以结合种类繁多的配体。
人补体蛋白C1q与C1r和C1s一起形成C1大分子，这是经典补体途径的个组成部分。免疫复合物与C1q的相互作用诱导C1复合物内的构象变化，这导致经典途径的激活。C1q通过结合IgG或IgM的重链（Fcγ。此外，C1q可以与凋亡泡结合，在那里它激活经典补体途径并介导吞噬作用。因此，C1q促进凋亡细胞的清除和随后自身抗原的暴露，从而防止免疫系统的刺激。
中文名称：C1q，人类，天然，1毫克
英文名字：C1q, Human, Natural, 1 mg
编号：HC2123
规格：1mg
用途：对于功能性研究，体外稀释必须在用户的实验环境中进行优化。
应用说明：C1q的生物活性定义为产生50%致敏红细胞（EA）裂解所需的C1q量。
储存和稳定性：在-70°C下储存。反复的冷冻和解冻循环将导致活性丧失。标签上标明了确切的有效期。解冻后24小时内使用C1q蛋白，并放在冰上。剩余金额应等分并立即重新冻结以备将来使用。等分试样不得多次解冻。在推荐的储存条件下，至少稳定一年。
仅供研究使用。不用于人体或动物或诊断。
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