Cell-surface protein identified on phagocytic cells modulates the C1q-mediated enhancement of phagocytosis.
Cell-surface protein identified on phagocytic cells modulates the C1q-mediated enhancement of phagocytosis.
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DOI：
10.4049/jimmunol.152.8.4005
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发表时间：
1994-04
影响因子：
4.4
通讯作者：
E. Guan;S. L. Robinson;E. Goodman;A. Tenner
中科院分区：
文献类型：
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作者：
E. Guan;S. L. Robinson;E. Goodman;A. Tenner
C1q是经典C通路第一组分的亚基，与免疫系统的特定细胞结合，引发多种细胞反应。为了鉴定吞噬细胞上的功能C1qR，用从U937细胞中分离的c1q结合蛋白或完整的U937细胞免疫产生单克隆抗体。免疫沉淀和Western blot分析表明，R139 （IgG2b）、R3 （IgM）和U40.3 （IgG1）三种单克隆抗体识别相同的100,000 M(r)蛋白（还原条件下为126,000 M(r)）。这些单抗还能从U937的洗涤剂提取物中共免疫沉淀CD43，这与该C1qR是一个多亚基结构的可能性相一致。两种抗体，R3和R139，而不是U40.3，持续抑制单核细胞粘附在C1q或C1q的胶原样片段（C1q- clf）上的吞噬增强。有趣的是，结合抑制研究表明，R139和U40.3都不能阻断[125I]C1q-CLF与U937细胞的结合，而R3确实抑制了[125I]C1q-CLF与这些细胞结合的35%至45%。因此，这三种单克隆抗体识别100,000 M(r)多肽的不同表位，该多肽是单核细胞C1qR的一个组成部分，调节吞噬作用。这三种单克隆抗体都能识别中性粒细胞、单核细胞和U937细胞上的分子胞外结构域，但分别对CEM或RAJI细胞、T和B淋巴母细胞样细胞系不起反应。此外，这三种单抗都没有抑制或模拟c1q介导的中性粒细胞对超氧化物产生的刺激，这表明介导增强吞噬的C1qR至少在一些关键参数上与介导中性粒细胞产生超氧化物的C1qR不同。
C1q, a subunit of the first component of the classical C pathway, binds to specific cells of the immune system, triggering a variety of cellular responses. To identify the functional C1qR on phagocytic cells, mAbs were generated by immunization with either C1q-binding proteins isolated from U937 cells or intact U937 cells. Immunoprecipitation followed by Western blot analysis demonstrated that three mAbs, designated R139 (IgG2b), R3 (IgM), and U40.3 (IgG1), recognize the same 100,000 M(r) protein (126,000 M(r) under reducing conditions). These mAbs also co-immunoprecipitate CD43 from detergent extracts of U937, consistent with the possibility that this C1qR is a multi-subunit structure. Two Abs, R3 and R139, but not U40.3, consistently inhibited the enhancement of phagocytosis by monocytes adhered to either C1q or the collagen-like fragment of C1q (C1q-CLF). Interestingly, binding inhibition studies demonstrated that neither R139 nor U40.3 blocked the binding of [125I]C1q-CLF to U937 cells, whereas R3 did inhibit 35 to 45% of the binding of [125I]C1q-CLF to these cells. Thus, the three mAbs recognize distinct epitopes of a 100,000 M(r) polypeptide that is a component of the monocyte C1qR that modulates phagocytosis. All three mAbs recognize the extracellular domain of the molecule on neutrophils, monocytes, and U937 cells, but were not reactive with CEM or RAJI cells, T and B lymphoblastoid cell lines, respectively. Furthermore, none of these three mAbs inhibited or mimicked the C1q-mediated stimulation of superoxide production by neutrophils, suggesting that the C1qR that mediates the enhancement of phagocytosis differs in at least some critical parameter from the C1qR that mediates superoxide generation by the neutrophil.