Kupffer cells are liver-resident macrophages that play an important role in mediating immune-related functions in mammals and humans. They are well-known for their capacity to phagocytose large amounts of waste complexes, cell debris, microbial particles and even malignant cells. Location, appearance and functional aspects are important features used to identify these characteristic cells of the liver sinusoid. To-date, there is limited information on the occurrence of macrophages in zebrafish liver. Therefore, we aimed to characterise the ultrastructural and functional aspects of liver-associated macrophages in the zebrafish model by taking advantage of the latest advances in zebrafish genetics and multimodal correlative imaging. Herein, we report on the occurrence of macrophages within the zebrafish liver exhibiting conventional ultrastructural features (e.g. presence of pseudopodia, extensive lysosomal apparatus, a phagolysosome and making up ∼3% of the liver volume). Intriguingly, these cells were not located within the sinusoidal vascular bed of hepatic tissue but instead resided between hepatocytes and lacked phagocytic function. While our results demonstrated the presence and structural similarities with liver macrophages from other experimental models, their functional characteristics were distinctly different from Kupffer cells that have been described in rodents and humans. These findings illustrate that the innate immune system of the zebrafish liver has some distinctly different characteristics compared to other animal experimental models. This conclusion underpins our call for future studies in order to have a better understanding of the physiological role of macrophages residing between the parenchymal cells of the zebrafish liver.

枯否细胞是肝脏常驻的巨噬细胞，在哺乳动物和人类中介导免疫相关功能中起重要作用。它们以吞噬大量废物复合物，细胞碎片，微生物颗粒甚至恶性细胞的能力而闻名。位置，外观和功能方面是用于识别肝窦特征细胞的重要特征。迄今为止，关于斑马鱼肝脏中巨噬细胞发生的信息有限。因此，我们旨在通过利用斑马鱼遗传学和多峰相关成像的最新进展来表征斑马鱼模型中肝脏相关巨噬细胞的超微结构和功能方面。在这里例如假足，广泛的溶酶体装置，吞噬溶酶体，约占肝脏体积的3％）。有趣的是，这些细胞不是位于肝组织的正弦血管床内，而是位于肝细胞之间，缺乏吞噬功能。尽管我们的结果证明了与其他实验模型中的肝巨噬细胞的存在和结构相似性，但它们的功能特性却与啮齿动物和人类中描述的库普弗细胞明显不同。这些发现说明，与其他动物实验模型相比，斑马鱼肝脏的先天免疫系统具有一些明显不同的特征。