Treutiger C J, Scholander C, Carlson J, McAdam K P, Raynes J G, Falksveden L, Wahlgren M
Microbiology and Tumor Biology Center (MTC), Karolinska Institutet, Stockholm, Sweden, S-171 77.
Exp Parasitol. 1999 Dec;93(4):215-24. doi: 10.1006/expr.1999.4454.
Excessive sequestration of Plasmodium falciparum-infected (pRBC) and uninfected erythrocytes (RBC) in the microvasculature, cytoadherence, and rosetting, have been suggested to be correlated with the development of cerebral malaria. P. falciparum erythrocyte membrane protein-1 (PfEMP1) is the parasite-derived adhesin which mediates rosetting. Herein we show that serum proteins are crucial for the rosette formation of four strains of parasites (FCR3S1, TM284, TM180, and R29), whereas the rosettes of a fifth strain (DD2) are serum independent. Some parasites, e.g., FCR3S1, can be depleted of all rosettes by washes in heparin and Na citrate and none of the rosettes remain when the parasite is grown in foetal calf serum or ALBUMAX. Rosettes of other parasites are less sensitive; e.g., 20% of TM180 and R29 and 70% of TM284 rosettes still prevail after cultivation. A serum fraction generated by ion-exchange chromatography and poly-ethylene-glycol precipitation restored 50% of FCR3S1 and approx 40 to 100% of TM180 rosettes. In FCR3S1, antibodies to fibrinogen reverted the effect of the serum fraction and stained fibrinogen bound to the pRBC surface in transmission electron microscopy. Normal, nonimmune IgM and/or IgG was also found attached to the pRBC of the four serum-dependent strains as seen by surface immunofluorescens. Our results suggest that serum proteins, known to participate in rouleaux formation of normal erythrocytes, produce stable rosettes in conjunction with the recently identified parasite-derived rosetting ligand PfEMP1.
恶性疟原虫感染的红细胞（pRBC）和未感染的红细胞（RBC）在微血管中的过度隔离、细胞粘附和花结形成，被认为与脑型疟疾的发展相关。恶性疟原虫红细胞膜蛋白1（PfEMP1）是介导花结形成的寄生虫来源的粘附素。在此我们表明，血清蛋白对于四株寄生虫（FCR3S1、TM284、TM180和R29）的花结形成至关重要，而第五株寄生虫（DD2）的花结形成则不依赖血清。一些寄生虫，例如FCR3S1，通过用肝素和柠檬酸钠洗涤可去除所有花结，当寄生虫在胎牛血清或ALBUMAX中生长时，没有花结残留。其他寄生虫的花结则不太敏感；例如，TM180和R29的20%以及TM284的70%的花结在培养后仍然存在。通过离子交换色谱和聚乙二醇沉淀产生的血清组分可恢复50%的FCR3S1花结以及约40%至100%的TM180花结。在FCR3S1中，针对纤维蛋白原的抗体可逆转血清组分的作用，并在透射电子显微镜下对结合到pRBC表面的纤维蛋白原进行染色。通过表面免疫荧光观察发现，正常的非免疫IgM和/或IgG也附着在四株血清依赖性菌株的pRBC上。我们的结果表明，已知参与正常红细胞缗钱状形成的血清蛋白，与最近鉴定出的寄生虫来源的花结形成配体PfEMP1一起产生稳定的花结。
