Nofima, Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås, Norway.
Center for Evolutionary and Theoretical Immunology (CETI), Department of Biology, University of New Mexico, Albuquerque, NM, United States.
Front Immunol. 2021 Nov 16;12:769901. doi: 10.3389/fimmu.2021.769901. eCollection 2021.
The zebrafish is extensively used as an animal model for human and fish diseases. However, our understanding of the structural organization of its immune system remains incomplete, especially the mucosa-associated lymphoid tissues (MALTs). Teleost MALTs are commonly perceived as diffuse and scattered populations of immune cells throughout the mucosa. Yet, structured MALTs have been recently discovered in Atlantic salmon (), including the interbranchial lymphoid tissue (ILT) in the gills. The existence of the ILT was only recently identified in zebrafish and other fish species, highlighting the need for in-depth characterizations of the gill-associated lymphoid tissue (GIALT) in teleosts. Here, using 3-D high-resolution microscopy, we analyze the GIALT of adult zebrafish with an immuno-histology approach that reveals the organization of lymphoid tissues the labeling of T/NK cells with an antibody directed to a highly conserved epitope on the kinase ZAP70. We show that the GIALT in zebrafish is distributed over at least five distinct sub-regions, an organization found in all pairs of gill arches. The GIALT is diffuse in the pharyngeal part of the gill arch, the interbranchial septum and the filaments/lamellae, and structured in two sub-regions: the ILT, and a newly discovered lymphoid structure located along each side of the gill arch, which we named the Amphibranchial Lymphoid Tissue (ALT). Based on RAG2 expression, neither the ILT nor the ALT constitute additional thymi. The ALT shares several features with the ILT such as presence of abundant lymphoid cells and myeloid cells embedded in a network of reticulated epithelial cells. Further, the ILT and the ALT are also a site for T/NK cell proliferation. Both ILT and ALT show structural changes after infection with Spring Viraemia of Carp Virus (SVCV). Together, these data suggest that ALT and ILT play an active role in immune responses. Comparative studies show that whereas the ILT seems absent in most neoteleosts ("Percomorphs"), the ALT is widely present in cyprinids, salmonids and neoteleosts, suggesting that it constitutes a conserved tissue involved in the protection of teleosts the gills.
斑马鱼被广泛用作人类和鱼类疾病的动物模型。然而，我们对其免疫系统的结构组织的理解仍然不完整，特别是黏膜相关淋巴组织 (MALT)。硬骨鱼的 MALT 通常被认为是散布在整个黏膜中的免疫细胞的弥散群体。然而，最近在大西洋鲑鱼中发现了结构 MALT，包括鳃中的鳃间淋巴组织 (ILT)。ILT 在斑马鱼和其他鱼类中的存在最近才被发现，这凸显了深入研究硬骨鱼鳃相关淋巴组织 (GIALT)的必要性。在这里，我们使用 3-D 高分辨率显微镜，通过免疫组织化学方法分析成年斑马鱼的 GIALT，该方法揭示了淋巴组织的组织 用针对激酶 ZAP70 上高度保守表位的抗体标记 T/NK 细胞。我们表明，斑马鱼的 GIALT 分布在至少五个不同的亚区中，这种组织在所有对鳃弓的配对中都存在。GIALT 在鳃弓的咽部分、鳃间隔和鳃丝/薄片中是弥散的，在两个亚区中是结构的：ILT 和一个新发现的位于鳃弓两侧的淋巴结构，我们将其命名为鳃旁淋巴组织 (ALT)。根据 RAG2 表达，ILT 或 ALT 都不构成额外的胸腺。ALT 与 ILT 具有几个共同特征，例如存在大量嵌入网状上皮细胞网络中的淋巴样细胞和髓样细胞。此外，ILT 和 ALT 也是 T/NK 细胞增殖的部位。ILT 和 ALT 在感染鲤鱼春病毒血症病毒 (SVCV) 后都发生结构变化。总的来说，这些数据表明 ALT 和 ILT 在免疫反应中发挥积极作用。比较研究表明，虽然 ILT 在大多数新鳍鱼类 ("鲈形目") 中似乎不存在，但 ALT 在鲤科鱼类、鲑科鱼类和新鳍鱼类中广泛存在，这表明它构成了一个保守的组织，参与了硬骨鱼 鳃的保护。
