Heterobothrium okamotoi, a monogenean gill parasite, exhibits high host specificity for the tiger puffer, Takifugu rubripes, and it has been experimentally verified that the parasite cannot colonize either closely related species such as the grass puffer Takifugu niphobles or distantly related fish such as the red seabream Pagrus major. Previously, we demonstrated in T. rubripes that immunoglobulin M (IgM) with d-mannose affinity induced deciliation of the oncomiracidia, the first step of parasitism, indicating that the parasite utilizes the molecule as a receptor for infection. In the present study, we purified mannose-specific IgM from 2 nonhost species, T. niphobles and P. major, by affinity and gel-filtration chromatography techniques and compared their deciliation-inducing activity against H. okamotoi oncomiracidia. The IgM of the former showed activity, whereas the latter had no effect, suggesting that in addition to d-mannose-binding ability, the crystallizable fragment domain of IgM, which is not part of the antigen-binding domain, plays an important role in host recognition by the oncomiracidia, such as direct binding to the parasites. It also suggests that the host specificity of H. okamotoi is relatively low upon initial recognition, and the specificity is established by exclusion in nonhosts during a later stage.

中文翻译：

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草河豚（Takifugu niphobles）中的D-甘露糖特异性免疫球蛋白M是单寄生性外寄生物冈本变种的非寄主鱼，可以触发其寄生。

单基因moto寄生虫冈本氏疟原虫对虎河豚（Takifugu rubripes）表现出很高的宿主特异性，并且已经通过实验验证了该寄生虫不能定殖于紧密相关的物种，例如草河豚T（Takifugu Niphobles）或远缘鱼类（例如红色）鲷Pagrus专业。先前，我们在丁香假单胞菌中证明了具有d-甘露糖亲和力的免疫球蛋白M（IgM）诱导了喜怒无常的消退，这是寄生虫的第一步，表明该寄生虫利用该分子作为感染的受体。在本研究中，我们通过亲和和凝胶过滤色谱技术从2个非寄主物种T. niphobles和P. major纯化了甘露糖特异性IgM，并比较了它们对冈本氏嗜酸杆菌的诱导诱导活性。前者的IgM具有活性，而后者则没有作用，这表明除d-甘露糖结合能力外，不是抗原结合域一部分的IgM的可结晶片段结构域在其中起着重要作用。宿主可通过喜怒无常来识别，例如直接结合到寄生虫上。这也表明冈本氏菌的宿主特异性在最初识别时相对较低，并且该特异性是通过在稍后阶段排除在非宿主中而建立的。