Development of a simple procedure for the isolation of secretory IgA by lectin affinity chromatography and its clinical application.

菠萝蜜种子中的凝集素是一种LGA特异性结合凝集素。我们收集了几批来自菲律宾、新加坡和日本等不同国家的菠萝蜜种子，发现其中一批菠萝蜜种子与人LgA1亚类的LGA特异结合，而不与LgA2亚类的LGA结合。用LgA1特异性凝集素(JAXALIN-P)制成的亲和层析柱可用于分离LgA1亚类分泌型LGA。该柱还用于从常规纯化的人乳LGA中分离分泌型LGA中的LgA1和LgA2。通过对该凝集素糖特异性的分析，我们得出结论：在LgA1铰链中存在但在LgA2亚类中缺失的寡糖Gal1-3GalNAc是导致该凝集素具有LgA1特异性的原因。进一步分析这种凝集素(JAXALIN-H)，发现它还结合聚集的LGG和免疫复合体。使用Jacalin-H亲和层析柱有效地去除了丙种球蛋白制剂中聚集的LGG和免疫复合体以及天然单体LGG以外的免疫球蛋白。这样处理的人丙种球蛋白制剂不具有抗补体活性，由于它只含有天然单体LGG，因此将适用于包括选择性免疫球蛋白缺乏症在内的各种免疫缺陷患者的安全免疫球蛋白制剂。

A lectin from jackfruit seeds ( Artocarpus integrifolia ) was first reported to be an LgA-specific binding lectin. We have collected several batches of jackfruit seeds from different countries, including the Phillippines, Singapore and Japan, and found that a batch of seeds from the Phillippines specifically bound human LgA of LgA1 subclass but not LgA2 subclass. The affinity column made from the LgA1-specific lectin ( jacalin-P ) could be used for the isolation of secretory LgA of LgA1 subclass. This column was also used for the separation of LgA1 and LgA2 of secretory LgA from conventionally purified human milk LgA. Analysis of sugar specificity of jacalin-P led to a conclusion that the oligosaccharide, Gal 1-3GalNAc, which is present in LgA1 hinge but is absent in LgA2 subclass, was responsible for the LgA1-specificty of the lectin.Among the lectins other than the jacalin-P, we found a lectin that bound every immunoglobulin other than LgA. Further analysis of this lectin ( jacalin-H ) disclosed that it also bound aggregated LgG and immune-complex. The use of jacalin-H affinity column efficiently removed the aggregated LgG and immune-complex as well as immunoglobulins other than native monomeric LgG from gamma-globulin preparations. The human gamma-globulin preparation thus treated was free from anti-complementary activity and will be applicable as a safe immunoglobulin preparation for various immune-deficient patients, including selective immunoglobulin deficiency, since it consisted of only native monomeric LgG.