Lackie A M, Vasta G R
Department of Zoology, University, Glasgow, U.K.
Immunology. 1988 Jun;64(2):353-7.
Agglutinating activity of the major serum lectin of Periplaneta americana against mammalian erythrocytes has been found previously to be inhibited most effectively by galactose and glycoproteins rich in non-reducing terminal galactose, such as porcine stomach mucin (PSM) and desialylated fetuin and bovine submaxillary mucin. Antibody raised against the purified lectin was found, by immunofluorescence, to bind to the surface of washed fixed haemocytes (the cells responsible for cellular immunity in insects). The experiments described here were carried out in order to investigate whether or not the lectin plays any role in mediating the haemocytic response, by measuring the in vivo cellular response to galactose- or sialic acid-rich glycoproteins, either in solution or conjugated to Sepharose beads. Comparison of the ability of injected solutions to stimulate haemocytic aggregates (nodules) showed that PSM, whether native, desialylated or pronase-digested to produce small galactose-containing fragments, stimulated large numbers of nodules, in contrast to either sialic acid-rich glycoproteins such as bovine submaxillary mucin (BSM) and fetuin, or the protein bovine serum albumen (BSA). Multicellular capsules formed around Sepharose conjugated to galactose-rich molecules such as PSM, asialo-PSM, asialo-fetuin or asialo-BSM were highly significantly thicker than those formed around control untreated beads, whereas capsules around BSA, fetuin or BSM conjugates were significantly thinner. It is unlikely that the different results for sialylated and desialylated molecules are due merely to a non-specific charge effect, since the response due to charge alone is directly opposite to that found when specific carbohydrate groups are considered. The results tentatively support the idea that soluble and/or cell-associated lectins may be involved in immuno-recognition in insects.
先前已发现，美洲大蠊主要血清凝集素对哺乳动物红细胞的凝集活性最有效地受到半乳糖以及富含非还原末端半乳糖的糖蛋白（如猪胃粘蛋白（PSM）、去唾液酸胎球蛋白和牛颌下粘蛋白）的抑制。通过免疫荧光发现，针对纯化凝集素产生的抗体可与洗涤后的固定血细胞（昆虫中负责细胞免疫的细胞）表面结合。开展此处所述的实验，是为了通过测量在体内对溶液中或与琼脂糖珠偶联的富含半乳糖或唾液酸的糖蛋白的细胞反应，来研究凝集素是否在介导血细胞反应中发挥任何作用。比较注射溶液刺激血细胞聚集体（结节）的能力表明，PSM，无论是天然的、去唾液酸的还是经链霉蛋白酶消化以产生含半乳糖的小片段，都能刺激大量结节形成，这与富含唾液酸的糖蛋白（如牛颌下粘蛋白（BSM）和胎球蛋白）或蛋白质牛血清白蛋白（BSA）形成对比。围绕与富含半乳糖的分子（如PSM、去唾液酸PSM、去唾液酸胎球蛋白或去唾液酸BSM）偶联的琼脂糖形成的多细胞胶囊，比围绕未处理的对照珠形成的胶囊显著更厚，而围绕BSA、胎球蛋白或BSM偶联物的胶囊则显著更薄。唾液酸化和去唾液酸化分子的不同结果不太可能仅仅归因于非特异性电荷效应，因为仅电荷引起的反应与考虑特定碳水化合物基团时发现的反应直接相反。这些结果初步支持了可溶性和/或细胞相关凝集素可能参与昆虫免疫识别的观点。
