Väkevä A, Laurila P, Meri S
Department of Bacteriology and Immunology, University of Helsinki, Finland.
Lab Invest. 1992 Nov;67(5):608-16.
Protectin (CD59) is a recently discovered inhibitor of the complement membrane attack complex (MAC). In the present study we investigated expression of protectin in human heart and examined the relationship between MAC deposition and protectin in myocardial infarction.
Myocardial tissue specimens were obtained at autopsy from patients who had died of myocardial infarction (n = 10) or other causes (n = 5). MAC and protectin were detected by indirect immunofluorescence microscopy analysis in the heart sections by using antibodies against individual components of MAC, MAC neoantigens and protectin. Myocardial protectin was purified by affinity chromatography and compared with the previously characterized erythrocyte and urinary protectins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, N-terminal amino acid sequencing, and testing its ability to bind to the terminal complement complex. The possible glycophosphoinositol-type anchorage of protectin in the heart was examined by treating myocardial sections with glycophosphoinositol-specific phospholipase C.
Immunoblotting and immunofluorescence analysis showed expression of protectin in the sarcolemmal membranes of normal myocardium. Protectin purified from normal human heart tissue had the same molecular weight and N-terminal amino acid sequence as CD59 purified from urine. In sucrose density ultracentrifugation analysis it was observed to bind efficiently to the SC5b-8 complex. In normal myocardium the expression of CD59 was sensitive to treatment with glycophosphoinositol-specific phospholipase C. The expression of CD59 was lost or clearly diminished in infarcted lesions aged 1-14 days. Loss of CD59 expression was accompanied by concomitant deposition of the MAC within the CD59-negative lesions. In border areas between an infarcted lesion and normal tissue, CD59 often appeared in small vesicles, suggesting shedding as a possible mechanism for its removal.
Glycophosphoinositol-anchored CD59 is expressed in the sarcolemmal membranes of normal heart but lost from infarcted myocardium. Acquired loss of resistance to autologous complement and subsequent complement attack may thus be involved in the pathophysiology of myocardial infarction.
保护素（CD59）是最近发现的补体膜攻击复合物（MAC）抑制剂。在本研究中，我们调查了保护素在人心脏中的表达，并研究了心肌梗死中MAC沉积与保护素之间的关系。
从死于心肌梗死（n = 10）或其他原因（n = 5）的患者尸检中获取心肌组织标本。通过使用针对MAC单个成分、MAC新抗原和保护素的抗体，在心脏切片中通过间接免疫荧光显微镜分析检测MAC和保护素。通过亲和层析纯化心肌保护素，并通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析、N端氨基酸测序以及测试其与末端补体复合物结合的能力，将其与先前表征的红细胞和尿液保护素进行比较。通过用糖基磷脂酰肌醇特异性磷脂酶C处理心肌切片，研究保护素在心脏中可能的糖基磷脂酰肌醇型锚定。
免疫印迹和免疫荧光分析显示保护素在正常心肌的肌膜中表达。从正常人心脏组织中纯化的保护素与从尿液中纯化的CD59具有相同的分子量和N端氨基酸序列。在蔗糖密度超速离心分析中，观察到它能有效地与SC5b-8复合物结合。在正常心肌中，CD59的表达对糖基磷脂酰肌醇特异性磷脂酶C的处理敏感。在1至14天的梗死病变中，CD59的表达丧失或明显减少。CD59表达的丧失伴随着MAC在CD59阴性病变中的沉积。在梗死病变与正常组织之间的边界区域，CD59常出现在小泡中，提示脱落可能是其清除的一种机制。
糖基磷脂酰肌醇锚定的CD59在正常心脏的肌膜中表达，但在梗死心肌中丧失。对自身补体的抗性丧失以及随后的补体攻击可能参与了心肌梗死的病理生理学过程。
