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To observe the ultrastructural changes in the midgut epithelium of Ixodes sinensis after infesting rabbits immunized with Mr 105000 purified tick antigen.New Zealand rabbits were inoculated with Mr 105000 purified antigen by means of mutiple intradermal injection in foot pad, groin and back. Each immunized rabbit was infested by 30 female Ixodes sinensis. At 24 hours, 48 hours, 72 hours, 5 days and 8 days after infestation, three Ixodes sinensis in each group were observed for ultrastructural changes in the epithelium of their midgut.Histological examinations showed that with the time going, digestive cells of the ticks after infesting hosts became more and larger with dense and regularly arranged microvilli, enriched organella, distinct unit-membrane structure, and the appearance of tubli, small vacuole, numerous lipid droplets and hematin granules. These cells also developed a highly infolded basal lamina, forming a labyrinth system. The digestive cells of immunized group were however greatly damaged, whose number and volume were significantly different from control groups. From 24 to 48 hours after infestation, the midgut epithelium of Ixodes snenss showed pathological changes with the basal lamina becoming thinner, looser and broken; digestive cells damaged and vacuolated; microvilli decreased, shortened and irregularly arranged; the mitochondria swollen and its crests reduced, shortened and even with myeloid changes; the rough endoplasmic reticulum dilated; lipid droplets and hematin granules decreased; phagocytic and pinocytic activity weakened; and basal labyrinth system vacuolated. From 72 hours to 8 days after infestation, cells were severely damaged, organella were denatured and necrotic, nuclei showed pyknosis and cells lysed.The rabbits immunized with Mr 105000 purified ixodic protein have acquired the adoptive immunity against Ixodes sinensis; in the anti-tick immunity described above, the midgut of Ixodes sinensis is the major affected site. |
