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血吸虫病免疫学的新概念正在发展中,它是关系到这种寄生性蠕虫的独特生物学。在免疫性方面:血吸虫在终宿主群体内不繁殖,因此它的分布极分散,而绝大多数个体的感染度都很轻。这种生物学知识加上在人体缺乏产生免疫性的确证和在实验动物产生免疫性的“无规律”,提示了生态学而非免疫性是控制人血吸虫病的流行和感染度的主要因素。免疫诊断方面:血吸虫是多细胞生物,近来已证明它具有多种的交叉反应抗原,因而能够解释众所周知的用于诊断血吸虫病的血清学试验和皮内试验缺乏特异性的原因。免疫病理学方面:仅少量血吸虫卵(成虫不断地和大量地产出的虫卵)排出体外,积聚在宿主组织的虫卵周围发生肉芽肿性炎症,从而引起纤维性瘢痕,在重度感染者则导致肝脏血流或尿路阻塞。曼氏血吸虫卵周围的肉芽肿形成,已被证明是对虫卵分泌的可溶性抗原的一种细胞介导超敏反应。这些微量抗原都是特异的,无需佐剂,都能诱发和激起肉芽肿的形成以及迟发型皮内反应和在体外试验相关的迟发型超敏反应。可溶性虫卵抗原尚在提纯,并对其化学和物理特性进行分析。这些抗原经过诱发免疫的耐受性和封闭(免疫增强作用)等途径,试图用以调变肉芽肿性超敏反应。
New concepts of schistosomiasis immunology are evolving, and it is a unique biology that relates to this parasitic worm. On the immunological side: Schistosomes do not breed in the final host population, so their distribution is extremely fragmented, while the vast majority of individuals have a low degree of infectivity. This biological knowledge, together with the lack of evidence of immunity in the human body and the “irregularity” of immunity in experimental animals, suggests that ecology rather than immunity is a major factor in controlling the prevalence and infectivity of human schistosomiasis. Immunodiagnosis: Schistosoma is a multicellular organism that has recently been shown to have multiple cross-reacting antigens that could explain the lack of specificity of the well-known serological and intradermal tests used to diagnose schistosomiasis. Immunopathologically, only a small number of Schistosoma japonicum eggs, which develop continuously and in large numbers, produce granulomatous inflammation around the eggs of the host tissue, causing fibrotic scarring in severely infected individuals Liver blood flow or urinary tract obstruction. Granuloma formation around Schistosoma mansoni eggs has been shown to be a cell-mediated hypersensitivity to soluble antigens secreted by eggs. These trace antigens are specific and can induce and provoke the formation of granulomas without the adjuvant, as well as the delayed type of intradermal reaction and the delayed type hypersensitivity associated with in vitro testing. Soluble egg antigen is still being purified and its chemical and physical properties are analyzed. These antigens have been used to modulate granulomatous hypersensitivity through pathways that induce immune tolerance and blockade (immune potentiation).