Hiemstra P S, Gorter A, Stuurman M E, Van Es L A, Daha M R
Scand J Immunol. 1987 Aug;26(2):111-7. doi: 10.1111/j.1365-3083.1987.tb02243.x.
Jacalin, a D-galactose-specific lectin from jackfruit, interacts with human IgA and one or two other serum proteins. Incubation of jacalin with fresh human serum was shown to result in activation of the complement system. Therefore the mechanism of complement activation by jacalin was studied. Jacalin was extracted from jackfruit seeds (crude preparation) and purified to homogeneity by affinity chromatography on IgA-Sepharose to yield a pure preparation of jacalin. Both crude and pure jacalin were able to activate complement, accompanied by conversion of C3. Consumption of C1, C4 and C-1-inactivator (C-1-In) indicated involvement of the classical pathway. Aggregated IgG (AIgG) caused partial (38%) and jacalin induced complete consumption of C1-In functional activity. It was found upon Ouchterlony analysis that jacalin forms a precipitation line with purified C-1-In. In addition binding of 125I-C-1-In to jacalin-Sepharose was observed, and this binding was inhibitable by either secretory IgA or D-galactose. Next to binding of jacalin to C-1-In, jacalin was also shown to inhibit the functional activity of C-1-In. These results indicate that jacalin induces complement activation by inhibition of C-1-In function and thereby facilitates the activation of precursor C1 in either the absence or presence of low amounts of C1 activators.
嘉卡林是一种从菠萝蜜中提取的对D-半乳糖具有特异性的凝集素，它可与人IgA及其他一两种血清蛋白相互作用。研究发现，将嘉卡林与新鲜人血清共同孵育会导致补体系统激活。因此，对嘉卡林激活补体的机制展开了研究。从菠萝蜜种子中提取出嘉卡林（粗制品），并通过IgA-琼脂糖亲和层析将其纯化至同质，从而得到纯的嘉卡林制剂。粗制和纯制的嘉卡林均能激活补体，并伴有C3的转化。C1、C4和C1灭活剂（C1-In）的消耗表明经典途径参与其中。聚合IgG（AIgG）导致C1-In功能活性部分消耗（38%），而嘉卡林则使其完全消耗。通过双向免疫扩散分析发现，嘉卡林与纯化的C1-In形成沉淀线。此外，还观察到125I-C1-In与嘉卡林-琼脂糖的结合，且这种结合可被分泌型IgA或D-半乳糖抑制。除了嘉卡林与C1-In的结合外，还发现嘉卡林能抑制C1-In的功能活性。这些结果表明，嘉卡林通过抑制C1-In功能诱导补体激活，从而在缺乏或存在少量C1激活剂的情况下促进前体C1的激活。
