Diverse Epithelial Lymphocytes in Zebrafish Revealed Using a Novel Scale Biopsy Method

Area of Science:

• Immunology
• Zebrafish model systems
• Comparative immunology

Background:

• Zebrafish share conserved adaptive immune systems with humans, making them valuable models.
• Investigating zebrafish lymphocytes, particularly in peripheral tissues like the epidermis, remains underexplored.
• Limited availability of antibodies necessitates alternative methods for studying zebrafish immune cells.

Purpose of the Study:

• To establish a novel, nonlethal technique for sampling and analyzing zebrafish epidermal lymphocytes.
• To characterize lymphocyte populations within zebrafish scales and epidermis.
• To profile gene expression and assess the function of epidermal lymphocytes.

Main Methods:

• Developed a novel scale biopsy technique for longitudinal sampling of live zebrafish.
• Utilized confocal microscopy and flow cytometry to identify and quantify lymphocyte types in scales.
• Performed single-cell quantitative real-time PCR and RNA sequencing on lymphocytes from scales, thymus, and kidney marrow.
• Assessed lymphocyte function using a bead-ingestion assay.

Main Results:

• Identified multiple lymphocyte types, including canonical B and T cells, within zebrafish scales and epidermis.
• Discovered novel lymphocyte populations not previously described in zebrafish.
• Demonstrated dexamethasone-induced responses in epidermal lymphocytes via longitudinal scale sampling.
• Confirmed phagocytic activity in thymic, marrow, and epidermal lymphocytes.

Conclusions:

• Established a groundbreaking, nonlethal method for obtaining and studying zebrafish lymphocytes from scales.
• Provided the first comprehensive quantification, gene expression profiling, and functional analysis of zebrafish epidermal lymphocytes.
• Opened new avenues for investigating peripheral immune responses in zebrafish and understanding conserved lymphocyte biology.