Isolating Malignant and Non-Malignant B Cells from lck:eGFP Zebrafish

Summary

Transgenic lck:eGFP zebrafish express GFP highly in T lymphocytes, and have been used to study T cell development and acute lymphoblastic leukemia. This line can be used to study B cells, which express lck at lower levels. This protocol describes purification of malignant and non-malignant B cells from lck:eGFP zebrafish.

Abstract

Zebrafish (Danio rerio) are a powerful model to study lymphocyte development. Like mammals, D. rerio possess an adaptive immune system that includes B and T lymphocytes. Studies of zebrafish lymphopoiesis are difficult because antibodies recognizing D. rerio cell surface markers are generally not available, complicating isolation and characterization of different lymphocyte populations, including B-lineage cells. Transgenic lines with lineage-specific fluorophore expression are often used to circumvent this challenge. The transgenic lck:eGFP line has been used to study D. rerio T cell development, and has also been utilized to model T cell development and acute lymphoblastic leukemia (T-ALL). Although lck:eGFP fish have been widely used to analyze the T-lineage, they have not been used to study B cells. Recently, we discovered that many zebrafish B cells also express lck, albeit at lower levels. Consequently, lck:eGFP B cells likewise express low levels of GFP. Based on this finding, we developed a protocol to purify B-lineage cells from lck:eGFP zebrafish, which we report here. Our method describes how to utilize a fluorescent-activated cell sorter (FACS) to purify B cells from lck:eGFP fish or related lines, such as double-transgenic rag2:hMYC; lck:eGFP fish. In these lines, B cells, particularly immature B cells, express GFP at low but detectable levels, allowing them to be distinguished from T cells, which express GFP highly. B cells can be isolated from marrow, thymus, spleen, blood, or other tissues. This protocol provides a new method to purify D. rerio B cells, enabling studies focused on topics like B cell development and B lymphocyte malignancies.

Introduction

Zebrafish offer powerful attributes, such as genetic manipulability, high fecundity, optical translucency, and rapid development that facilitate studying vertebrate development using genetic approaches. These advantages, together with the shared features of teleost and mammalian hematopoiesis, make D. rerio ideal for in vivo analyses of lymphopoiesis and lymphocyte function, from their earliest appearance in larvae throughout adulthood. Blood development in zebrafish relies upon well-conserved genetic processes that are shared with mammals, and these extend to the adaptive immune system. Additionally, molecular mechanisms governing lymphoid development are re....

Protocol

All procedures involving zebrafish were approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Oklahoma Health Sciences Center.

1. Isolating Non-malignant B and T Lymphocytes from Transgenic lck:eGFP Fish

1. Anesthetize the fish using 0.02% tricaine (MS-222) in fish system water.
2. Examine 2–6 month old fish for fluorescent thymi, which are located at the dorsomedial aspect of the branchial cavity of zebrafish a.......

Discussion

We developed and provide a protocol to isolate B cells from lck:eGFP transgenic zebrafish, adding this to other D. rerio models with B-lineage labels^3,4. Somewhat surprisingly, the identification of GFP^lo B cells in this line went unnoticed since its description in 2004.Generally, lck is considered to be T cell-specific⁶, but recent studies found unexpected lck expression by natural killer and.......

Materials

Name	Company	Catalog Number	Comments
35 µm mesh	Sefar Filter technology	7050-1220-000-13
5 ml Polystyrene round-Bottom tube with cell-strainer cap	Falcon Corning Brand	352235
50 ml conical tube	VWR international	525-0448
AZ APO 100 Fluorescent microscope	Nikon
Cytoflex	Beckman Coulter
DS-Qi1MC camara	Nikon
Ethyl 3-aminobenzoate methansesulfonate; MS-222	Sigma	E-10521
FACSJazz	BD Biosciences
Fetal bovine Serum	Thermo Fisher	10437028
FlowJo v10.2	FlowJo, LLC
lck:eGFP			See Langeneu et al., 2004
NIS Elements software	Nikon	Version 4.13
Penicilin -Streptomycin	Sigma	P4333
Pestle micro-tube homogenizers	Electron Microscopy Sciences	64788-20
Plastic Transfer pippetes
rag2:hMYC-ER			See Gutierrez et al., 2011
RPMI Media 1640 1X	Life Technologies	11835-030