中华硬蜱叮咬不同免疫力新西兰兔后中肠上皮组织的形态动态变化

通过光镜和电镜观察了中华硬蜱Ixodes sinensis叮咬初次和再次感染宿主新西兰兔后不同时间（叮咬后24 h、48 h、72 h以及第 5天、第8天）中肠上皮组织的形态学动态变化。结果显示： 中华硬蜱叮咬前中肠上皮主要由替代细胞和少量体积较大的消化细胞构成；替代细胞数量多、体积小、呈圆形、胞质染色浅 。中华硬蜱叮咬初次感染宿主后，消化细胞随叮咬时间延长而增多增大，微绒毛较密集，排列整齐，胞质内细胞器丰富，各单位膜结构清晰，并出现顶端小管、小泡、大量脂滴和高铁血红素颗粒；近基膜的细胞膜内褶形成发达的基底迷路系统。中华硬蜱叮咬再次感染宿主后，中肠可发生一系列明显的病理变化，中肠基膜出现变薄、松散和断裂现象，消化细胞破裂、空泡化，消化细胞数量减少；消化细胞微绒毛减少、变短、排列不整，线粒体肿大，体嵴减少、变短甚至髓样变，粗面内质网扩张，脂粒及高铁血红素颗粒减少，细胞膜吞饮、吞噬现象减弱，消化细胞内结构紊乱和破坏。该研究结果提示初次叮咬导致了宿主的免疫抗性，再次叮咬后蜱中肠是宿主免疫力的主要作用部位。

Histological changes in the midgut epithelium of Ixodes sinensis after biting naive and immunized New Zealand white rabbits

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.