A tessellated lymphoid network provides whole-body T cell surveillance in zebrafish

Abstract

Homeostatic trafficking to lymph nodes allows T cells to efficiently survey the host for cognate antigen. Nonmammalian jawed vertebrates lack lymph nodes but maintain diverse T cell pools. Here, we exploit in vivo imaging of transparent zebrafish to investigate how T cells organize and survey for antigen in an animal devoid of lymph nodes. We find that naïve-like T cells in zebrafish organize into a previously undescribed whole-body lymphoid network that supports streaming migration and coordinated trafficking through the host. This network has the cellular hallmarks of a mammalian lymph node, including naïve T cells and CCR7-ligand expressing nonhematopoietic cells, and facilitates rapid collective migration. During infection, T cells transition to a random walk that supports antigen-presenting cell interactions and subsequent activation. Our results reveal that T cells can toggle between collective migration and individual random walks to prioritize either large-scale trafficking or antigen search in situ. This lymphoid network thus facilitates whole-body T cell trafficking and antigen surveillance in the absence of a lymph node system.

Identification of a pharyngeal mucosal lymphoid organ in zebrafish and other teleosts: Tonsils in fish?

“…S4 (A to D). In addition, the existence of NELO could be confirmed based on the expression of the kinase lck gene using the Tg(lck:EGFP) transgenic adult zebrafish ( 18 , 42 ), in which enhanced green fluorescent protein (EGFP) is highly expressed in T lymphocytes (fig. S4, E and F).…”

“…Further analysis showed that this lymphoid network extended beyond the branchial cavity region (fig. S11), likely connecting with the tessellated lymphoid network ( 42 ) via the operculum opening, as well as linking the pharyngeal epithelium and the esophagus epithelium (fig. S11A).…”

Fishing Innate Immune System Properties through the Transcriptomic Single-Cell Data of Teleostei

“…These datasets contain clusters of macrophages and could be further compared with macrophages in normal tissues. Also, there is a distinct dataset of T cells, GSE215189 [83] suitable for refining T cell markers from lymphoid tissue. In addition, we included in our datasets of interest scRNAseq experiments carried out on the neuronal tissues of zebrafish.…”