HUMAN-PLATELET FC RECEPTOR FOR IMMUNOGLOBULIN-G - IDENTIFICATION AS A 40,000-MOLECULAR-WEIGHT MEMBRANE-PROTEIN SHARED BY MONOCYTES
HUMAN-PLATELET FC RECEPTOR FOR IMMUNOGLOBULIN-G - IDENTIFICATION AS A 40,000-MOLECULAR-WEIGHT MEMBRANE-PROTEIN SHARED BY MONOCYTES
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DOI：
10.1172/jci112242
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发表时间：
1985-12-01
影响因子：
15.9
通讯作者：
ANDERSON, CL
中科院分区：
文献类型：
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作者：
ROSENFELD, SI;LOONEY, RJ;ANDERSON, CL
我们最近已经表明，人单核细胞和U937细胞具有两种分子类别的Fc γ。受体的一种是72，000-mol-wt唾液酸糖蛋白，对人和鼠单体IgG的某些亚类具有高亲和力。另一种是40，000-mol-wt蛋白（p40），对单体IgG具有低亲和力，但具有结合IgG聚集体或IgG包被颗粒的能力。在本研究中，一个40,000摩尔重量的单链蛋白，显然是相同的P40从U937细胞，从表面放射性碘标记的人血小板的亲和纯化使用鼠IgG 2b单克隆抗体p40。当使用对照IgG 2b或不相关的鼠单克隆抗体代替抗p40时，未观察到该40，000-mol-wt蛋白。同样的40，000-mol-wt蛋白质也从IgG-琼脂糖亲和吸附剂中回收，但不能从卵清蛋白或肌红蛋白-琼脂糖中回收。72，000-mol-wt Fc γ.在血小板上未鉴定出单核细胞的受体。来自该抗体的单克隆抗p40和Fab片段通过热聚集的人IgG阻断血小板聚集，而对照鼠IgG 2b蛋白在500- 1，000倍高浓度下几乎没有抑制作用。鼠IgG 1单克隆抗体，与无关的血小板特异性膜抗原反应，不抑制血小板对聚集IgG的反应。抗p40不影响凝血酶，胶原蛋白，或纤维蛋白原加ADP的血小板聚集。尽管在所用浓度下抗p40不直接聚集血小板，但与F（ab“）2山羊抗鼠IG的交联诱导抗p40处理的血小板的腺苷三磷酸双磷酸酶敏感性聚集。这表明，p40具有跨膜连接的血小板活化和分泌。这些观察结果有力地表明，这种新识别的40，000-mol-wt血小板膜蛋白充当Fc γ。受体的
We have recently shown that human monocytes and U937 cells possess two molecular classes of Fc.gamma. receptor. One, a 72,000-mol-wt sialoglycoprotein, has high affinity for certain subclasses of human and murine monomeric IgG. The other is a 40,000-mol-wt protein (p40) with low affinity for monomeric IgG but with the capacity to bind IgG aggregates or IgG-coated particles. In the present study, a 40,000-mol-wt single chain protein, apparently identical to p40 from U937 cells, was isolated from surface-radioiodinated human platelets by affinity purification using a murine IgG2b monoclonal antibody to p40. This 40,000-mol-wt protein was not seen when control IgG2b or unrelated murine monoclonal antibodies were employed in place of anti-p40. The same 40,000-mol-wt protein was also recovered from an IgG-Sepharose affinity adsorbent, but not from ovalbumin- or myoglobin-Sepharose. The 72,000-mol-wt Fc.gamma. receptor of monocytes was not identified on platelets. Monoclonal anti-p40 and Fab fragments derived from this antibody blocked platelet aggregation by heat-aggregated human IgG, whereas a control murine IgG2b protein had little or no inhibitory effect at 500-1,000-fold higher concentrations. A murine IgG1 monoclonal antibody, reactive with an unrelated platelet-specific membrane antigen, did not inhibit platelet responses to aggregated IgG. Anti-p40 did not affect platelet aggregation by thrombin, collagen, or fibrinogen plus ADP. Although anti-p40 did not directly aggregate platelets in the concentrations employed, cross-linking with F(ab'')2 goat anti-murine Ig induced apyrase-sensitive aggregation of anti-p40-treated platelets. This indicates that p40 possesses transmembrane linkage for platelet activation and secretion. These observations strongly suggest that this newly recognized 40,000-mol-wt platelet membrane protein serves as an Fc.gamma. receptor.