The activation of the complement cascade, a cornerstone of the innate immune response, produces a number of small (74-77 amino acid) fragments, originally termed anaphylatoxins, that are potent chemoattractants and secretagogues that act on a wide variety of cell types. These fragments, C5a, C4a, and C3a, participate at all levels of the immune response and are also involved in other processes such as neural development and organ regeneration. Their primary function, however, is in inflammation, so they are important targets for the development of antiinflammatory therapies. Only three receptors for complement peptides have been found, but there are no satisfactory antagonists as yet, despite intensive investigation. In humans, there is a single receptor for C3a (C3a receptor), no known receptor for C4a, and two receptors for C5a (C5a₁ receptor and C5a₂ receptor). The most recently characterized receptor, the C5a₂ receptor (previously known as C5L2 or GPR77), has been regarded as a passive binding protein, but signaling activities are now ascribed to it, so we propose that it be formally identified as a receptor and be given a name to reflect this. Here, we describe the complex biology of the complement peptides, introduce a new suggested nomenclature, and review our current knowledge of receptor pharmacology.

中文翻译：

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国际基础和临床药理学联盟。[更正]。LXXXVII。补体肽C5a，C4a和C3a受体。

补体级联反应的激活是先天免疫反应的基石，它会产生许多小的（74-77个氨基酸）片段，最初称为过敏毒素，它们是有效的趋化剂和促分泌素，可作用于多种细胞类型。这些片段C5a，C4a和C3a参与了免疫应答的所有水平，并且还参与了其他过程，例如神经发育和器官再生。然而，它们的主要功能是炎症，因此它们是抗炎疗法发展的重要目标。尽管进行了深入研究，但仅发现了三种补体肽受体，但尚无令人满意的拮抗剂。在人类中，只有一个C3a受体（C3a受体），没有已知的C4a受体，和两个C5a受体（C5a1受体和C5a2受体）。最近被鉴定为受体的C5a2受体（以前称为C5L2或GPR77）被认为是一种被动结合蛋白，但现在已将其信号活性归因于此，因此我们建议将其正式鉴定为受体并给予反映这一点的名称。在这里，我们描述了补体肽的复杂生物学，介绍了新的建议命名法，并回顾了我们目前对受体药理学的了解。