Otuka Hinata, Sato Ryoichi
Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588 Japan.
Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588 Japan.
J Insect Physiol. 2023 Mar;145:104486. doi: 10.1016/j.jinsphys.2023.104486. Epub 2023 Jan 18.
Nodule formation is a well-known process in cellular immunity of insects. However, few studies have investigated the role of hemocytes in rapid aggregation before tissue adhesion. In addition, since nodule formation is usually elicited by injecting large quantities of microbes, it remains unclear whether nodule formation is a natural response. The present study addressed these issues. A small number of nodules adhered to the dorsal vessels 1 min after Saccharomyces cerevisiae injection, while numerous aggregates of hemocytes and S. cerevisiae cells were observed in the hemolymph. The aggregate number decreased sharply after 5 min, corresponding to a rapid increase in the number of nodules. This suggests that aggregates formed in the hemolymph in response to S. cerevisiae injection eventually attached to the tissues. Nodules were induced using conditions that do not occur in nature, i.e., injection of nearly 2,000,000 S. cerevisiae cells. However, many aggregates contained only one S. cerevisiae cell, suggesting that aggregate formation can begin with the invasion of a single cell and that nodule formation is not an unnatural response. Biosynthesis inhibitors of serotonin (5-HT) and eicosanoids inhibited aggregate and nodule formation. In addition, injection of 5-HT and prostaglandin E2 induced hemocyte aggregation within 1 min in the hemolymph, along with hemocytin release. This suggested that 5-HT and eicosanoids induce rapid aggregation in response to invading microorganisms.
结节形成是昆虫细胞免疫中一个广为人知的过程。然而，很少有研究调查血细胞在组织黏附前快速聚集过程中的作用。此外，由于结节形成通常是通过注射大量微生物引发的，目前尚不清楚结节形成是否是一种自然反应。本研究解决了这些问题。在注射酿酒酵母1分钟后，少量结节附着于背血管，而在血淋巴中观察到大量血细胞和酿酒酵母细胞的聚集体。5分钟后聚集体数量急剧下降，与此同时结节数量迅速增加。这表明，注射酿酒酵母后在血淋巴中形成的聚集体最终附着于组织。结节是在自然界中不会出现的条件下诱导形成的，即注射近200万个酿酒酵母细胞。然而，许多聚集体仅包含一个酿酒酵母细胞，这表明聚集体形成可以从单个细胞的侵入开始，并且结节形成并非非自然反应。血清素（5-羟色胺，5-HT）和类花生酸的生物合成抑制剂抑制聚集体和结节形成。此外，注射5-HT和前列腺素E2可在1分钟内诱导血淋巴中的血细胞聚集，并伴随血细胞凝集素释放。这表明5-HT和类花生酸可诱导针对入侵微生物的快速聚集。
