Nonaka M, Azumi K
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan.
Dev Comp Immunol. 1999 Jun-Jul;23(4-5):421-7. doi: 10.1016/s0145-305x(99)00021-x.
To elucidate the molecular architecture and function of the possibly primitive complement system of the solitary ascidian. Halochynthia roretzi, cDNA clones for the third component (C3) and mannose-binding lectin (MBL)-associated serine protease (MASP) were isolated from the hepatopancreas cDNA library. The deduced primary structure of ascidian C3 (AsC3) shows overall similarity to mammalian C3 including a typical thioester site. Two distinct ascidian MASPs, termed AsMASPa and AsMASPb, have the same domain structure as mammalian Clr/ Cls/MASP-1/MASP-2. Both of them show a closer similarity to mammalian MASP-1 than to mammalian Clr/Cls/ MASP-2. Ascidian body fluid contains an opsonic activity which enhances phagocytosis of yeast by ascidian blood cells, and an antibody against AsC3 inhibits this opsonic activity. These results indicate that the lectin-dependent, opsonic complement system was present prior to the emergence of the vertebrates and well ahead of the establishment of adaptive immunity.
为阐明独居海鞘可能原始的补体系统的分子结构和功能，从柄海鞘的肝胰腺cDNA文库中分离出了第三补体成分（C3）和甘露糖结合凝集素（MBL）相关丝氨酸蛋白酶（MASP）的cDNA克隆。海鞘C3（AsC3）推导的一级结构与哺乳动物C3总体相似，包括一个典型的硫酯位点。两种不同的海鞘MASP，分别称为AsMASPa和AsMASPb，具有与哺乳动物Clr/Cls/MASP-1/MASP-2相同的结构域结构。它们与哺乳动物MASP-1的相似性比与哺乳动物Clr/Cls/MASP-2的相似性更高。海鞘体液具有调理活性，可增强海鞘血细胞对酵母的吞噬作用，并且针对AsC3的抗体可抑制这种调理活性。这些结果表明，凝集素依赖性调理补体系统在脊椎动物出现之前就已存在，并且远早于适应性免疫的建立。
