Isolation and Ex Vivo Culture of Vδ1+CD4+γδ T Cells, an Extrathymic αβT-cell Progenitor

Summary

Here, we provide an optimized protocol for the isolation and cloning of the scarce T-cell entity of peripheral Vδ1⁺CD4⁺ T cells that is, as we showed recently, an extrathymic αβ T-cell progenitor. This technique allows to quantitatively isolate, clone and efficiently expand these cells in ex vivo culture.

Abstract

The thymus, the primary organ for the generation of αβ T cells and backbone of the adaptive immune system in vertebrates, has long been considered as the only source of αβT cells. Yet, thymic involution begins early in life leading to a drastically reduced output of naïve αβT cells into the periphery. Nevertheless, even centenarians can build immunity against newly acquired pathogens. Recent research suggests extrathymic αβT cell development, however our understanding of pathways that may compensate for thymic loss of function are still rudimental. γδ T cells are innate lymphocytes that constitute the main T-cell subset in the tissues. We recently ascribed a so far unappreciated outstanding function to a γδ T cell subset by showing that the scarce entity of CD4⁺ Vδ1⁺γδ T cells can transdifferentiate into αβT cells in inflammatory conditions. Here, we provide the protocol for the isolation of this progenitor from peripheral blood and its subsequent cultivation. Vδ1 cells are positively enriched from PBMCs of healthy human donors using magnetic beads, followed by a second step wherein we target the scarce fraction of CD4⁺ cells with a further magnetic labeling technique. The magnetic force of the second labeling exceeds the one of the first magnetic label, and thus allows the efficient, quantitative and specific positive isolation of the population of interest. We then introduce the technique and culture condition required for cloning and efficiently expanding the cells and for identification of the generated clones by FACS analysis. Thus, we provide a detailed protocol for the purification, culture and ex vivo expansion of CD4⁺ Vδ1⁺γδ T cells. This knowledge is prerequisite for studies that relate to this αβT cell progenitor`s biology and for those who aim to identify the molecular triggers that are involved in its transdifferentiation.

Introduction

In vertebrates, adaptive immunity that is structured in the cellular and a humoral part of immunity plays a major role in the defense against pathogens. The recognition of a wide range of antigens is mediated by hyperpolymorphic T- and B cell receptors (TCR/BCR), which with regard to T cells are assumed to be produced mainly in the thymus¹. Thereto, hematopoietic stem cells (HSCs), derived from bone marrow, seed the thymus and differentiate along well-defined stages finally giving rise to all T cell lineages. Thymus seeding progenitors are CD4^- and CD8^- and thus constitute the immature, double negative (DN) thymocyte fraction. Thymus-d....

Protocol

Ethic Statement: All procedures were carried out according to the Declaration of Helsinki and were approved by the Clinical Ethics Committee at the University of Tübingen (projects 38/2009B02 and 470/2013B02).

1. Isolation of Peripheral Blood Mononuclear Cells (PBMCs)

1. Take 50-100 ml from a healthy volunteer via venipuncture using a 50 ml syringe containing 1,000 IU heparin sulfate and dilute the blood 1:2 with PBS (pH = 7.2).
2. Carefully layer 35 ml of the blood:PBS solution on 15 ml blood separating solution such as Biocoll (d = 1.077 g/ml) in a 50 ml conical tube. Centrifuge for 15 min at 800 x g at RT.
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Results

Figure 1 depicts the different stages and the outcome of the isolation of Vδ1 T cells from peripheral blood. Figure 1A shows a typical distribution of Vδ1⁺ cells in CD3⁺ lymphocytes, as well as the co-receptor expression of the Vδ1⁺ population. In this donor, the frequency of Vδ1⁺ cells (red) is 2.3% of total lymphocyte counts and the CD4 expression (green) of Vδ1⁺ lymphocytes is 2.6%. Altogether, the target population for isolation .......

Discussion

To study the phenotype, biology and function of a scarce (T-) cell entity, namely Vδ1⁺CD4⁺ T cells, we used two markers: Vδ1 and CD4 for its positive magnetic cell isolation. Vδ1 is an orphan receptor, whereas CD4 is expressed on T helper cells, at a lower level on monocytes and dendritic cells, and at a very low level on hematopoietic progenitor cells.

Techniques for the enrichment and selection of cells in high purity include Fluorescence activated cell s.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Biocoll Solution	Biochrom	L 6113	lymphocyte separating solution
Lysing Buffer	BD BioSciences	555899	lysis of erythrocytes
Phosphate-buffered Saline	Sigma Aldrich	D8537
MACS buffer	Miltenyi Biotec	130-091-222	supplement with BSA and pre-cool before use
BSA	Miltenyi Biotec	130-091-376	not mandatorily from this supplier
anti-human Vd1 FITC (clone:  TS8.2)	Thermo Scientific	TCR2730	not mandatorily from this supplier
anti-human CD3 PerCP (clone: SK7)	BD BioSciences	345766	not mandatorily from this supplier or this flurochrome
anti-human TCRab PE (clone: T10B9.1A-31)	BD BioSciences	555548	not mandatorily from this supplier or this flurochrome
anti-human CD4 VioBlue (clone: M-T466)	Miltenyi Biotec	130-097-333	not mandatorily from this supplier or this flurochrome
anti-human CD8 APC-H7 (clone: SK1)	BD BioSciences	641400	not mandatorily from this supplier or this flurochrome
Anti-FITC MultiSort Kit	Miltenyi Biotec	130-058-701	yields better results than anti-FITC MicroBeads
MS columns	Miltenyi Biotec	130-042-201	pre-cool before use
MiniMACS Separator	Miltenyi Biotec	130-042-102
CD4 Positive Isolation Kit	life technologies	11331D