Urban J F, Alizadeh H, Romanowski R D
Helminthic Diseases Laboratory, U.S. Department of Agriculture, Beltsville, Maryland 20705.
Exp Parasitol. 1988 Jun;66(1):66-77. doi: 10.1016/0014-4894(88)90051-3.
The development of protective immunity to Ascaris suum was examined in pigs naturally exposed to eggs on a contaminated dirt lot. Pigs became almost totally immune to second-stage larvae migrating from the intestines because few larvae from a challenge inoculum could be found in the lungs, and liver white-spot lesions (an immunopathologic response to migrating larvae) were absent. Blood from these pigs contained lymphocytes that responded blastogenically to larval antigens in vitro, while the serum contained antibody to larval antigens. Immunity was related to parasite exposure and not to the age of the host, and was not affected by the removal of adult A. suum from the intestines. Naturally exposed pigs responded to a variety of A. suum antigens with an immediate-type skin reactivity, and their intestinal mucosa contained relatively large numbers of mast cells and eosinophils. Other pigs were maintained on a dirt lot not contaminated with A. suum eggs and the effects of common environmental conditions on development of resistance to A. suum were studied. Resistance also developed in these pigs because 72% fewer larvae were detected in their lungs following a challenge exposure than in control pigs confined indoors on concrete floors and challenged similarly. This response was not expressed at the intestinal level, however, because their livers had numerous, intense white-spot lesions. To verify that the intestinal immunity that developed in pigs after natural exposure to A. suum was a direct result of homologous infection and not related to other stimuli encountered on a dirt lot, pigs maintained indoors on concrete floors, free from inadvertent helminthic infection, were inoculated orally with A. suum eggs daily for 16 weeks. Intestinal immunity was induced because larvae from a challenge inoculum were not detected in the lungs, and few white-spot lesions appeared on the livers of these pigs. Apparently, continual exposure of the intestinal mucosa to larvae eventually elicits the appropriate effector components necessary to prevent larval migration from the intestines.
在一块被污染的脏地上自然接触虫卵的猪中，研究了对猪蛔虫保护性免疫的发展情况。猪对从肠道迁移的二期幼虫几乎完全免疫，因为在肺部几乎找不到攻击接种物中的幼虫，且肝脏没有白点病变（对迁移幼虫的免疫病理反应）。这些猪的血液中含有在体外对幼虫抗原产生增殖反应的淋巴细胞，而血清中含有幼虫抗原抗体。免疫与寄生虫暴露有关，而与宿主年龄无关，并且不受从肠道清除成年猪蛔虫的影响。自然接触的猪对多种猪蛔虫抗原表现出速发型皮肤反应性，其肠道黏膜含有相对大量的肥大细胞和嗜酸性粒细胞。其他猪饲养在未被猪蛔虫卵污染的脏地上，研究了常见环境条件对猪蛔虫抗性发展的影响。这些猪也产生了抗性，因为在攻击暴露后，它们肺部检测到的幼虫比饲养在室内水泥地板上并接受类似攻击的对照猪少72%。然而，这种反应在肠道水平上未表现出来，因为它们的肝脏有许多严重的白点病变。为了验证猪自然接触猪蛔虫后在肠道产生的免疫是同源感染的直接结果，而非与脏地上遇到的其他刺激有关，将饲养在室内水泥地板上、无意外蠕虫感染的猪，每天口服猪蛔虫卵，持续16周。诱导了肠道免疫，因为在这些猪的肺部未检测到攻击接种物中的幼虫，且它们肝脏上出现的白点病变很少。显然，肠道黏膜持续接触幼虫最终会引发阻止幼虫从肠道迁移所需的适当效应成分。
