Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Faculty of Science, University of South Bohemia, Branisovská, Ceské Budĕjovice, Czech Republic.
Adv Exp Med Biol. 2010;708:137-62.
Ticks are blood feeding parasites transmitting a wide variety of pathogens to their vertebrate hosts. The vector competence of ticks is tightly linked with their immune system. Despite its importance, our knowledge of tick innate immunity is still inadequate and the limited number of sufficiently characterized immune molecules and cellular reactions are dispersed across numerous tick species. The phagocytosis of microbes by tick hemocytes seems to be coupled with a primitive complement-like system, which possibly involves self/nonself recognition by fibrinogen-related lectins and the action of thioester-containing proteins. Ticks do not seem to possess a pro-phenoloxidase system leading to melanization and also coagulation of tick hemolymph has not been experimentally proven. They are capable of defending themselves against microbial infection with a variety of antimicrobial peptides comprising lysozymes, defensins and molecules not found in other invertebrates. Virtually nothing is known about the signaling cascades involved in the regulation of tick antimicrobial immune responses. Midgut immunity is apparently the decisive factor of tick vector competence. The gut content is a hostile environment for ingested microbes, which is mainly due to the antimicrobial activity of hemoglobin fragments generated by the digestion of the host blood as well as other antimicrobial peptides. Reactive oxygen species possibly also play an important role in the tick-pathogen interaction. The recent release of the Ixodes scapularis genome and the feasibility of RNA interference in ticks promise imminent and substantial progress in tick innate immunity research.
蜱是吸血寄生虫，会将多种病原体传播给脊椎动物宿主。蜱的媒介能力与其免疫系统密切相关。尽管蜱的先天免疫非常重要，但我们对其的了解仍然不足，并且数量有限的充分特征化的免疫分子和细胞反应分散在许多蜱种中。蜱血细胞吞噬微生物似乎与原始的补体样系统相关联，该系统可能涉及纤维蛋白原相关凝集素的自我/非自我识别以及含硫酯蛋白的作用。蜱似乎没有导致黑化的原酚氧化酶系统，也没有实验证明蜱血淋巴的凝固。它们能够利用各种抗菌肽来防御微生物感染，这些肽包括溶菌酶、防御素和其他无脊椎动物中未发现的分子。关于调节蜱抗菌免疫反应的信号级联几乎一无所知。中肠免疫显然是蜱媒介能力的决定性因素。肠道内容物是摄入微生物的恶劣环境，这主要是由于宿主血液消化产生的血红蛋白片段以及其他抗菌肽的抗菌活性。活性氧物种在蜱-病原体相互作用中可能也发挥着重要作用。新近发布的肩突硬蜱基因组和在蜱中进行 RNA 干扰的可行性有望在蜱先天免疫研究方面取得重大进展。
