关键词: 中华硬蜱, 新西兰兔, 免疫反应, 中肠上皮组织, 形态变化

Abstract: The histological changes in the midgut epithelium of Ixodes sinensis were examined under light microscope and electron microscope at different times (24 h, 48 h, 72 h, 5 d and 8 d) after the first biting on naive New Zealand rabbits and the second biting on the rabbits immunized by the first biting. The results indicated that after the first biting, the digestive cells of I. Sinensis become more in number and larger in size, with microvilli closely and regularly arranged, organelles enriched, unit membrane clearly seen, and vacuoles, a large number of lipid droplets and haematin granules appearing. These cells also developed a highly infolded basal lamina, forming a labyrinth system. By contrast, after the second biting, the midgut epithelium of I. Sinensis revealed rather strikingly pathological changes with the basal lamina becoming thinner, looser and broken; digest cells damaged and vacuolated; microvilli decreased in number, shortened and disarranged; the mitochondria swollen and its crests reduced, shortened and even with myeloid changed; the rough endoplasmic reticulum dilated; lipid droplets and haematin granules decreased in number; phagocytic and pinocytic activity weakened; and basal labyrinth system vacuolized. The results suggested that the first biting results in immunodefense reaction of hosts and the tick midgut was the primary immunological target of hosts after the second biting.

Key words: Ixodes sinensis, New Zealand white rabbit, immunological reaction, midgut epithelium, morphological changes