S. SirisinhaW. RattanasiriwilaiS. PuengtomwatanakulP. SobhonP. saitongdeeT. KoonchornboonMahidol University2018-02-272018-02-271986-01-01International Journal for Parasitology. Vol.16, No.4 (1986), 341-346002075192-s2.0-0022535533https://repository.li.mahidol.ac.th/handle/123456789/9735A lethal effect was observed adult Ophisthorchis viverrini was exposed to fresh normal sera from different species of animals as well as from individuals with no clinical history of opisthorchiasis. The effects of guinea pig and hamster sera were minimal when compared with human, rat and rabbit sera. Studies performed using ethylenediamine tetraacetic acid (EDTA) and heat inactivation at 56 °C for 30 min indicated that the parasiticidal activity was complement dependent. Further, by using ethyleneglycol tetraacetic acid (EGTA) and Mg 2+ , zymosan, heat inactivation at 50 ° C for 15 min, or prior absorption of the serum with anti-factor B, it was possible to conclude that O. viverrini activated the complement via the alternative pathway. The lethal effect was associated at least in part with the damage of the surface tegument as demonstrated by scanning electron microscopic examination, in which the stubby microvilli swelled within 15 min of exposure to fresh normal human serum. Within 30 min a large number of the swollen microvilli ruptured, resulting in the appearance of crater-like lesions on the surface. In some areas the lesions were so extensive that the underlying musculature was exposed. © 1986.Mahidol UniversityImmunology and MicrobiologyMedicineArticleSCOPUS10.1016/0020-7519(86)90112-8