Pennock J L, Behnke J M, Bickle Q D, Devaney E, Grencis R K, Isaac R E, Joshua G W, Selkirk M E, Zhang Y, Meyer D J
Immunology Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel St., London WC1E 7HT, UK.
Biochem J. 1998 Nov 1;335 ( Pt 3)(Pt 3):495-8. doi: 10.1042/bj3350495.
Macrophage-migration-inhibition factor (MIF) is an essential stimulator of mammalian T-lymphocyte-dependent adaptive immunity, hence MIF orthologues might be expressed by infectious organisms as an immunosubversive stratagem. Since MIF actively catalyses the tautomerization of the methyl ester of l-dopachrome (using dopachrome tautomerase), the occurrence of MIF orthologues in several parasitic helminths was investigated by assaying and characterizing such activity. Evidence of MIF orthologues (dopachrome tautomerase) was found in the soluble fraction of the nematodes Trichinella spiralis (stage 4 larvae) and Trichuris muris (adults), and the filarial nematode Brugia pahangi (adults). The MIF orthologues of Tr. muris (TmMIF) and B. pahangi (BpMIF) were purified to homogeneity using phenyl-agarose chromatography, that of T. spiralis (TsMIF) required a further step: cation-exchange FPLC. Retention time on reverse-phase HPLC and Mr on SDS/PAGE of the nematode MIFs were similar to those of human MIF. N-terminal sequences (19 residues) of TsMIF and TmMIF showed 47 and 36% identity, respectively, with human MIF. The N-terminal sequence of BpMIF (14 residues) was identical to that of an MIF orthologue in the genome of B. malayi (Swiss-Prot, P91850) and showed 43% identity to either human or TsMIF. TsMIF had 10-fold higher dopachrome tautomerase activity than MIF from the other sources. The enzyme activities of TsMIF, BpMIF and TmMIF were less sensitive to inhibition by haematin (I50: >15 microM, >15 microM and 2.6 microM, respectively) than that of human MIF (I50 0.2 microM). Significant dopachrome tautomerase or phenyl-agarose-purifiable MIF-like protein was not detected in the soluble fraction of the nematodes Heligmosomoides polygyrus and Nippostrongylus brasiliensis, the cestode Hymenolepis diminuta, or the trematodes Schistosoma mansoni, S. japonicum and S. haematobium, or the free-living nematode, Caenorhabditis elegans, which does contain an MIF-related gene.
巨噬细胞移动抑制因子（MIF）是哺乳动物T淋巴细胞依赖性适应性免疫的重要刺激因子，因此MIF同源物可能被感染性生物体表达作为一种免疫颠覆策略。由于MIF能催化左旋多巴色素甲酯的互变异构（利用多巴色素互变异构酶），因此通过检测和表征这种活性来研究几种寄生蠕虫中MIF同源物的存在情况。在旋毛虫（4期幼虫）、鼠鞭虫（成虫）和马来布鲁线虫（成虫）的线虫可溶性组分中发现了MIF同源物（多巴色素互变异构酶）的证据。鼠鞭虫的MIF同源物（TmMIF）和马来布鲁线虫的MIF同源物（BpMIF）通过苯基琼脂糖层析纯化至均一，旋毛虫的MIF同源物（TsMIF）还需要进一步步骤：阳离子交换快速蛋白质液相色谱法。线虫MIF在反相高效液相色谱上的保留时间和在十二烷基硫酸钠/聚丙烯酰胺凝胶电泳上的相对分子质量与人MIF的相似。TsMIF和TmMIF的N端序列（19个残基）分别与人MIF有47%和36%的同源性。BpMIF的N端序列（14个残基）与马来丝虫基因组中的一个MIF同源物相同（瑞士蛋白质数据库，P91850），与人或TsMIF有43%的同源性。TsMIF的多巴色素互变异构酶活性比其他来源的MIF高10倍。TsMIF、BpMIF和TmMIF的酶活性对血红素抑制的敏感性低于人MIF（半数抑制浓度：分别>15μM、>15μM和2.6μM，而人MIF为0.2μM）。在多形螺旋线虫、巴西日圆线虫、微小膜壳绦虫、曼氏血吸虫、日本血吸虫、埃及血吸虫的可溶性组分中，以及在确实含有一个MIF相关基因的自由生活线虫秀丽隐杆线虫中，均未检测到显著的多巴色素互变异构酶或苯基琼脂糖可纯化的MIF样蛋白。
