iC3b is a protein fragment that is part of the complement system, a component of the vertebrate immune system. iC3b is produced when complement factor I cleaves C3b. [1] Complement receptors on white blood cells are able to bind iC3b, so iC3b functions as an opsonin.

补体分子的受体及相关生物学作用 C3b和C4b（后者仅由经典途径产生）结合到CR1，而iC3b结合到CR3（Mac-1）和CR4。 CR1本身在诱导C3b包裹的微生物的吞噬作用方面效率不高，但如果微生物被包裹，则其能力得到增强。

2022年4月12日 · Recognition of iC3b by complement receptor type 3 (CR3) fosters pathogen opsonophagocytosis by macrophages and the stimulation of adaptive immunity by complement-opsonized antigens. Here, we...

2022年5月4日 · C3b cleavage to iC3b occurred quickly on the surface of S. aureus in human serum, similar to the iC3b generation observed on EA. Unlike the case for EA, in which all C3b had been cleaved to iC3b after 30 min in serum, iC3b and C3b were bound to the S. aureus surface after 30 min in serum.

C3 是一种β 球蛋白,由α和β两条多肽链组成,分子量分别是110kD和75kD.α链有998个氨基酸残基,β链有669个氨基酸残基；两链间以氢键、疏水键及二硫键相连,相互平行.α链参与C3活化,链的第77位 精氨酸 和78位丝氨酸之间的 肽键 是C3裂解酶的作用部位.C3裂解后产生小 ...

细胞表面的补体激活导致 C3b、iC3b 和 C3dg（主要的补体调理素）大量沉积。 3 型补体受体 (CR3) 对 iC3b 的识别促进了巨噬细胞对病原体的调理吞噬和补体调理抗原对适应性免疫的刺激。

CR3 is a β 2-integrin that mediates binding of neutrophils to endothelial cells and is critical for neutrophil recruitment to sites of infection. CR3 mediates phagocytosis of iC3b-coated microbes, enables extravasation of leukocytes from the circulation to sites of injury or infection and facilitates homing of lymphocytes to tissues.

2020年12月12日 · Complement fragment iC3b serves as a major opsonin for facilitating phagocytosis via its interaction with complement receptors CR3 and CR4, also known by their leukocyte integrin family names, αMβ2 and αXβ2, respectively.

2021年6月15日 · Upon interaction with CR3, iC3b rearranges to form a compact receptor–ligand complex. Overall, the data suggest that the iC3b–CR3 interaction is of high affinity and relies on minor contacts formed between CR3 and regions outside the iC3b thioester domain.

2017年4月4日 · Complement-mediated opsonization, phagocytosis, and immune stimulation are critical processes in host defense and homeostasis, with the complement activation fragment iC3b playing a key effector role. To date, however, there is no high-resolution structure of iC3b, and some aspects of its structure-activity profile remain controversial.