Oteifa N M, Moustafa M A, el-Gozamy B R, Oteifa N M
Department of Parasitology, Faculty of Medicine, Ain Shams University, Cairo, Egypt.
J Egypt Soc Parasitol. 1996 Dec;26(3):629-38.
Congenital parasitic infections may not lead to any overt clinical effects but could modulate the foetal future immune response to the same parasite depending on whether sensitization or tolerance has occurred in utero. In this study, pregnant female mice were infected with Toxocara canis eggs at different gestational age, then the offspring were next challenged with Toxocara eggs 6 weeks after birth and their immune response was assessed by estimation of the eosinophilic count and serum IgE concentration. The Total larval count (TLC), brain parasitism (BP) and reduction % in (TLC) were used as criteria for the course of infection. It was found that exposure to infection during pregnancy whether early or late led not only to transmission of larvae to the foetus but also to modulation of its immune response and course of infection when next encountered the parasite after birth. The offspring when compared to control from non-infected mothers were hyporesponsive when infection occurred early during pregnancy and they showed high immune responsiveness when infection was induced late in pregnancy. The potential clinical application of these findings was suggested. It is now an established fact that immunocompetence in the mammalian foetus including humans develops very early in utero. Therefore, the foetus is capable of showing some forms of activity against invasion by maternal pathogenic organisms or their antigens (Loke, 1978). Moreover, the early contact with parasitic antigens may affect the foetus future immune response when it next encounters similar organisms after birth. Palmer (1978) reported a rapid secondary immune response in the offspring of Plasmodium berghei infected female rats when challenged with the parasite and compared to control groups from non-infected mothers. An apposite response was reported by Hang et al. (1974) who noticed that massive infection of pregnant mice with Schistosoma mansoni cercariae resulted in offspring hyporesponsive to subsequent challenge assessed by the diameter of the egg granulomas. Considering that toxocariasis is a frequent and potentially serious disease affecting primarily young children, also congenital toxocariasis was well documented since the original studies of Fulleborn (1921), this study was designed to reveal the extent to which the foetus future immune response can be modulated by maternal toxocariasis in experimental animals. The estimation of the immune response included IgE level (antibody mediated mechanism) and the absolute eosinophils count (a manifestation of cell mediated immune response) since eosinophil/IgE/mast cell axis represents a specialized immune mechanism that may contribute directly to parasite damage in toxocariasis (Knight, 1982). Also, (TLC), (B.P) and reduction % in (TLC) were used as criteria for the course of infection.
先天性寄生虫感染可能不会导致任何明显的临床症状，但根据胎儿在子宫内是否发生致敏或耐受，可能会调节其未来对同一寄生虫的免疫反应。在本研究中，怀孕的雌性小鼠在不同的孕期感染犬弓首蛔虫卵，然后在其后代出生6周后用犬弓首蛔虫卵进行攻击，并通过嗜酸性粒细胞计数和血清IgE浓度评估它们的免疫反应。总幼虫计数（TLC）、脑内寄生虫感染（BP）和（TLC）的降低百分比被用作感染过程的标准。结果发现，孕期暴露于感染，无论早期还是晚期，不仅会导致幼虫传播给胎儿，还会调节其免疫反应以及出生后再次接触寄生虫时的感染过程。与未感染母亲的对照组相比，孕期早期感染的后代反应低下，而孕期晚期感染的后代则表现出高免疫反应性。这些发现的潜在临床应用得到了提示。现在已经确定的事实是，包括人类在内的哺乳动物胎儿的免疫能力在子宫内很早就开始发育。因此，胎儿能够对母体致病生物或其抗原的入侵表现出某种形式的反应（洛克，1978年）。此外，早期接触寄生虫抗原可能会影响胎儿出生后再次遇到类似生物时的未来免疫反应。帕尔默（1978年）报道，感染伯氏疟原虫的雌性大鼠的后代在用该寄生虫攻击时会出现快速的二次免疫反应，并与未感染母亲的对照组进行了比较。杭等人（1974年）报道了一个恰当的反应，他们注意到用曼氏血吸虫尾蚴大量感染怀孕小鼠会导致后代对随后通过虫卵肉芽肿直径评估的攻击反应低下。考虑到弓首蛔虫病是一种主要影响幼儿的常见且潜在严重的疾病，自富勒伯恩（1921年）的最初研究以来，先天性弓首蛔虫病也有充分的文献记载，本研究旨在揭示母体弓首蛔虫病在实验动物中能在多大程度上调节胎儿未来的免疫反应。免疫反应的评估包括IgE水平（抗体介导机制）和绝对嗜酸性粒细胞计数（细胞介导免疫反应的一种表现），因为嗜酸性粒细胞/I gE/肥大细胞轴代表一种特殊的免疫机制，可能直接导致弓首蛔虫病中的寄生虫损伤（奈特，1982年）。此外，（TLC）、（BP）和（TLC）的降低百分比被用作感染过程的标准。
