Membrane complement receptor type three (CR3) has lectin-like properties analogous to bovine conglutinin as functions as a receptor for zymosan and rabbit erythrocytes as well as a receptor for iC3b.
Membrane complement receptor type three (CR3) has lectin-like properties analogous to bovine conglutinin as functions as a receptor for zymosan and rabbit erythrocytes as well as a receptor for iC3b.
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DOI：
10.4049/jimmunol.134.5.3307
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发表时间：
1985-05
影响因子：
4.4
通讯作者：
G. D. Ross;J. A. Cain;P. Lachmann
中科院分区：
文献类型：
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作者：
G. D. Ross;J. A. Cain;P. Lachmann
人类白细胞补体受体三型（CR 3）被证明是凝集素样的，并且类似于牛血清胶凝素（K），因为它与iC 3b和未调理的酵母（酿酒酵母）结合，并被EDTA或N-乙酰基-D-葡萄糖胺（NADG）抑制。CR 3和K还结合到酵母聚糖（Z），酵母细胞壁提取物，其主要含有多糖并且没有可检测的蛋白质。然而，牛吞噬细胞上的结构差异和K的缺乏表明CR 3不是牛K的人类同源物。吞噬和呼吸系统的反应unopsonized Z的CR 3依赖，因为它们被抑制的α链的CR 3特异性的单克隆抗体，并没有发生与患者的吞噬细胞与CR 3的遗传缺陷。CR 3与Z的结合不需要Z与嗜中性粒细胞分泌的C3的调理作用，因为Z结合和应答不被Fab抗C3抑制。此外，CR 3依赖性结合的酵母发生与中性粒细胞的蛋白质分泌被阻断固定与多聚甲醛。兔红细胞（RaE）也与中性粒细胞CR 3弱结合，并引发摄入。抗CR 3不仅阻断RaE的结合和摄取，而且选择性地阻断RaEC 3b的摄取，而不影响CR 1介导的强结合。尽管绵羊E和绵羊EC 3b没有被中性粒细胞摄入，但抗CR 3对绵羊EAIgG摄入的抑制作用为20%至40%，这表明CR 3与绵羊E的结合较弱。这种抑制作用仅在允许CR 3结合位点活性的缓冲液中观察到，而在含有EDTA或NADG的缓冲液中未观察到。一个明显矛盾的发现是，Z的弱CR 3依赖性结合引发了中性粒细胞摄入和超氧化物爆发，而绵羊EC 3bi的贪婪CR 3依赖性结合没有诱导显著的摄入或呼吸爆发。对CR 3 α链不同表位特异性单克隆抗体的阻断研究表明，这可能是由于CR 3中存在两个不同的结合位点：一个位点用于不触发功能的固定iC 3b，第二个功能触发位点用于不与固定iC 3b结合的Z。
Human leukocyte complement receptor type three (CR3) was shown to be lectin-like and to resemble bovine serum conglutinin (K) in that it bound to both iC3b and unopsonized yeast (Saccharomyces cerevisiae), and was inhibited by EDTA or N-acetyl-D-glucosamine (NADG). CR3 and K also bound to zymosan (Z), a yeast cell wall extract that contains primarily polysaccharide and no detectable protein. However, structural differences and the absence of K on bovine phagocytes indicated that CR3 was not the human homologue of bovine K. Phagocytic and respiratory responses to unopsonized Z were CR3 dependent because they were inhibited by monoclonal antibodies specific for the alpha-chain of CR3 and did not occur with phagocytes from patients with a genetic deficiency of CR3. The binding of CR3 to Z did not require opsonization of the Z with neutrophil-secreted C3, as Z binding and responses were not inhibited by Fab anti-C3. In addition, CR3-dependent binding of yeast occurred with neutrophils from which protein secretion was blocked by fixation with paraformaldehyde. Rabbit erythrocytes (RaE) also bound weakly to neutrophil CR3 and triggered ingestion. Anti-CR3 not only blocked the binding and ingestion of RaE but also blocked selectively the ingestion of RaEC3b without affecting the strong binding mediated by CR1. Even though sheep E and sheep EC3b were not ingested by neutrophils, a weak binding of CR3 to sheep E was suggested by the finding of 20 to 40% inhibition of sheep EAIgG ingestion by anti-CR3. Such inhibition was only observed in buffers that allowed activity of the CR3 binding site and not in buffers containing either EDTA or NADG. An apparently contradictory finding was that the weak CR3-dependent binding of Z triggered neutrophil ingestion and a superoxide burst, whereas the avid CR3-dependent binding of sheep EC3bi did not induce significant ingestion or a respiratory burst. Blocking studies with monoclonal antibodies specific for different epitopes of the alpha-chain of CR3 suggested that this might result from the presence of two distinct binding sites in CR3: one site for fixed iC3b that did not trigger functions, and a second function-triggering site for Z that did not bind to fixed iC3b.