Despite the apparent simplicity of the body organization of echinoderms, their immune system is competent to perform a complex innate immune response, which is far from being well understood. The echinoderms represent the most advanced invertebrates that form a bridge with the primitive chordates. In fact, they possess numerous receptors and effectors that are used to obtain a fast immune response. After an infection, the humoral and cellular immune response determines a network in which the main protagonists are membrane and endosomal receptors. The recognition of nonself molecules by specific membrane receptors triggers the immune response, stimulating consecutive intracellular events. We have previously shown how the polyinosinic–polycytidylic acid (polyI:C) that mimics a viral infection is able to induce an immune response in the sea urchin Paracentrotus lividus immune cells. It activates a specific membrane receptor belonging to the Toll‐like receptor (TLR) family. Here, we show the activated expression pattern of some genes involved in the downstream cascade of TLR signalling pathway, such as Pl‐Tbk and Pl‐Irf, whose partial sequence was isolated from P. lividus immune cells. Their mRNA expression increases consequentially to the polyI:C stimulation and in a temporal way. In addition, we analysed the expression of Pl‐NF‐kB and we found that its upregulation was time‐dependent, preceding Pl‐Tbk and Pl‐Irf increase. Protein analysis showed that also some cytokine (TNF‐α and IL‐1α) expression increased after polyI:C insult. Therefore, the purpose of this study was to discover the molecular mechanisms of the innate defence strategies, similarly to vertebrates, implemented by the sea urchins in order to cope with viral infection challenge.

中文翻译：

---

Paracentrotus lividus 海胆病毒侵袭后先天免疫反应的进化保守途径

尽管棘皮动物的身体组织明显简单，但它们的免疫系统有能力执行复杂的先天免疫反应，这远未得到很好的理解。棘皮动物代表了与原始脊索动物形成桥梁的最先进的无脊椎动物。事实上，它们拥有大量的受体和效应器，用于获得快速的免疫反应。感染后，体液和细胞免疫反应决定了一个网络，其中主要的主角是膜和内体受体。特定膜受体对非自身分子的识别触发免疫反应，刺激连续的细胞内事件。我们之前已经展示了聚肌苷酸 - 聚胞苷酸 (polyI: C) 模拟病毒感染能够在海胆 Paracentrotus lividus 免疫细胞中诱导免疫反应。它激活属于 Toll 样受体 (TLR) 家族的特定膜受体。在这里，我们展示了一些参与 TLR 信号通路下游级联的基因的激活表达模式，例如 Pl-Tbk 和 Pl-Irf，其部分序列是从青紫霉免疫细胞中分离出来的。它们的 mRNA 表达随 polyI:C 刺激而增加，并以时间方式增加。此外，我们分析了 Pl-NF-kB 的表达，我们发现它的上调是时间依赖性的，先于 Pl-Tbk 和 Pl-Irf 增加。蛋白质分析表明，polyI:C 损伤后一些细胞因子（TNF-α 和 IL-1α）表达也增加。所以，