In jawless vertebrates, the lamprey complement component C1q (LC1q) acts as a lectin and activates lamprey complement component C3 (LC3) in association with mannose-binding lectin (MBL)-associated serine protease (MASP) via the lectin pathway. Furthermore, LC1q may interact with variable lymphocyte receptor B (VLRB) in a complex with antigens and mediate the activation of LC3, leading to cytolysis. In the present study, we found, for the first time, that LC1q plays a critical role in VLRA/VLRC-mediated immune response. Escherichia coli, Shigella flexneri, Aeromonas hydrophila, Pseudomonas plecoglossicida, Aeromonas allosaccharophila, P. luteola, Brevundimonas diminuta, and Bacillus cereus were isolated from infected Lampetra morii in our laboratory and identified using the 16s rRNA method. A. hydrophila was confirmed as a rapidly spreading lethal pathogen in the larvae of L. morii and was used in subsequent immune stimulation experiments. The results of real-time quantitative polymerase chain reaction (Q-PCR) and immunofluorescence analyses indicated that the RNA and protein expression levels of LC1q were upregulated following exposure to 107 cfu/mL of A. hydrophila, compared to the levels of the naïve group. We obtained LC1q morphants (LC1q MO) of lamprey larvae by morpholino-mediated knockdowns. We found that LC1q played key roles in the embryonic development of lamprey. The median lethal time (LT50) of LC1q MO larvae was 2 d after being exposed to the pathogens, whereas the LT50 of control MO was 5 d. The drastic decrease in LT50 values after LC1q knockdown implies that LC1q plays a critical role in lamprey immune response. Gene expression profiles of LC1q-deficient A. hydrophila, control MO A. hydrophila, wild type A. hydrophila, and naive 1-month-old ammocoetes larvae were compared by examining the expression levels of a selected panel of orthologous genes. It is worth mentioning that LC1q MO affected the VLRA+/VLRC + population genes but did not affect the VLRB + populations. Immunohistochemical data indicated that LC1q deficiency also affected VLRA and VLRC but not VLRB. Thus, LC1q plays a critical role in VLRA/VLRC-mediated immune response in lamprey.

中文翻译：

---

补体成分 C1q 在 VLRA/VLRC 介导的免疫反应中起着关键作用。

在无颌脊椎动物中，七鳃鳗补体成分 C1q (LC1q) 充当凝集素并通过凝集素途径激活与甘露糖结合凝集素 (MBL) 相关丝氨酸蛋白酶 (MASP) 相关的七鳃鳗补体成分 C3 (LC3)。此外，LC1q 可能与抗原复合物中的可变淋巴细胞受体 B (VLRB) 相互作用并介导 LC3 的激活，导致细胞溶解。在本研究中，我们首次发现 LC1q 在 VLRA/VLRC 介导的免疫反应中起着关键作用。在我们的实验室中，从受感染的 Lampetra morii 中分离出大肠杆菌、福氏志贺氏菌、嗜水气单胞菌、多糖假单胞菌、异糖气单胞菌、黄原虫、Brevundimonas diminuta 和蜡状芽孢杆菌，并使用 16s rRNA 方法进行鉴定。一种。嗜水菌被证实是一种在森氏乳杆菌幼虫中迅速传播的致死病原体，并用于随后的免疫刺激实验。实时定量聚合酶链反应 (Q-PCR) 和免疫荧光分析的结果表明，与未处理组的水平相比，暴露于 107 cfu/mL 的嗜水杆菌后，LC1q 的 RNA 和蛋白质表达水平上调. 我们通过吗啉代介导的敲低获得了七鳃鳗幼虫的 LC1q morphant (LC1q MO)。我们发现 LC1q 在七鳃鳗的胚胎发育中起关键作用。LC1q MO 幼虫暴露于病原体后的中位致死时间（LT50）为 2 天，而对照 MO 的 LT50 为 5 天。LC1q 敲低后 LT50 值的急剧下降意味着 LC1q 在七鳃鳗免疫反应中起着关键作用。通过检查一组选定的直系同源基因的表达水平，比较了 LC1q 缺陷型 A.hydrophila、对照 MO A.hydrophila、野生型 A.hydrophila 和 1 月龄幼虫的基因表达谱。值得一提的是，LC1q MO影响了VLRA+/VLRC+群体基因，但不影响VLRB+群体。免疫组织化学数据表明，LC1q 缺乏也影响 VLRA 和 VLRC，但不影响 VLRB。因此，LC1q 在七鳃鳗的 VLRA/VLRC 介导的免疫反应中起着关键作用。值得一提的是，LC1q MO影响了VLRA+/VLRC+群体基因，但不影响VLRB+群体。免疫组织化学数据表明，LC1q 缺乏也影响 VLRA 和 VLRC，但不影响 VLRB。因此，LC1q 在七鳃鳗的 VLRA/VLRC 介导的免疫反应中起着关键作用。值得一提的是，LC1q MO影响了VLRA+/VLRC+群体基因，但不影响VLRB+群体。免疫组织化学数据表明，LC1q 缺乏也影响 VLRA 和 VLRC，但不影响 VLRB。因此，LC1q 在七鳃鳗的 VLRA/VLRC 介导的免疫反应中起着关键作用。