The host defence of insects includes a combination of cellular and humoral responses. The cellular arm of the insect innate immune system includes mechanisms that are directly mediated by haemocytes (e.g., phagocytosis, nodulation and encapsulation). In addition, melanization accompanying coagulation, clot formation and wound healing, nodulation and encapsulation processes leads to the formation of cytotoxic redox-cycling melanin precursors and reactive oxygen and nitrogen species. However, demarcation between cellular and humoral immune reactions as two distinct categories is not straightforward. This is because many humoral factors affect haemocyte functions and haemocytes themselves are an important source of many humoral molecules. There is also a considerable overlap between cellular and humoral immune functions that span from recognition of foreign intruders to clot formation. Here, we review these immune reactions starting with the cellular mechanisms that limit haemolymph loss and participate in wound healing and clot formation and advancing to cellular functions that are critical in restricting pathogen movement and replication. This information is important because it highlights that insect cellular immunity is controlled by a multilayered system, different components of which are activated by different pathogens or during the different stages of the infection.

中文翻译：

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昆虫中血细胞介导的免疫：对抗病原体和寄生虫的细胞、过程和相关成分

昆虫的宿主防御包括细胞和体液反应的结合。昆虫先天免疫系统的细胞臂包括由血细胞直接介导的机制（例如吞噬作用、结节和包囊）。此外，伴随凝固、凝块形成和伤口愈合、结节和包封过程的黑色化导致细胞毒性氧化还原循环黑色素前体以及活性氧和氮物质的形成。然而，细胞免疫反应和体液免疫反应作为两个不同类别的界限并不简单。这是因为许多体液因素影响血细胞功能，而血细胞本身就是许多体液分子的重要来源。细胞免疫功能和体液免疫功能之间也存在相当大的重叠，从识别外来入侵者到凝块形成。在这里，我们回顾这些免疫反应，从限制血淋巴损失、参与伤口愈合和凝块形成的细胞机制开始，再发展到对限制病原体运动和复制至关重要的细胞功能。这一信息很重要，因为它强调昆虫细胞免疫是由多层系统控制的，其中的不同组成部分由不同的病原体或在感染的不同阶段激活。