Real-time Monitoring of Mitochondrial Respiration in Cytokine-differentiated Human Primary T Cells

Summary

Metabolic adaptation is fundamental for T cells as it dictates differentiation, persistence, and cytotoxicity. Here, an optimized protocol for monitoring mitochondrial respiration in ex vivo cytokine-differentiated human primary T cells is presented.

Abstract

During activation, the metabolism of T cells adapts to changes that impact their fate. An increase in mitochondrial oxidative phosphorylation is indispensable for T cell activation, and the survival of memory T cells is dependent on mitochondrial remodeling. Consequently, this affects the long-term clinical outcome of cancer immunotherapies. Changes in T cell quality are often studied by flow cytometry using well-known surface markers and not directly by their metabolic state. This is an optimized protocol for measuring real-time mitochondrial respiration of primary human T cells using an Extracellular Flux Analyzer and the cytokines IL-2 and IL-15, which differently affect T cell metabolism. It is shown that the metabolic state of T cells can clearly be distinguished by measuring the oxygen consumption when inhibiting key complexes in the metabolic pathway and that the accuracy of these measurements is highly dependent on optimal inhibitor concentration and inhibitor injection strategy. This standardized protocol will help implement mitochondrial respiration as a standard for T cell fitness in monitoring and studying cancer immunotherapies.

Introduction

Correct T cell development and function are essential for the ability of the immune system to recognize and respond to antigens. Mitochondrial oxidative phosphorylation (OxPhos) changes according to the state of the T cell. Naïve T cells predominantly use OxPhos to produce ATP, whereas activated T cells undergo a metabolic transition where glycolysis becomes dominant¹. After the effector phase, the small remaining subset of memory T cells reverts to a metabolic state dominated by OxPhos^2,3. The changes of OxPhos follow the differentiation of T cells to such a degree that even subse....

Protocol

Experiments were carried out under the guidelines from Herlev Hospital and the Capital Region of Denmark.

NOTE: This protocol contains instructions for both an Optimization run and an Assays run. It is clearly written in the text when instructions are for an Optimization run or an Assay run. Run an Optimization run before continuing with the Assay runs

1. Human peripheral blood mononuclear (PBMC) isolation from buffy coats

1. PBMC isolation
   1. Collect buffy coats from the appropriate institution (collected in blood collection bags). Buffy coats originate from healthy donors. Exc....

Results

A correct determination of OxPhos properties is an indispensable tool when studying T cells. However, if the assay conditions have not been optimized, there is a substantial risk of misleading or erroneous results. In this protocol, there is a strong focus on the optimization of cell number per well and concentrations of oligomycin and FCCP to be used. In the described setup, oligomycin and FCCP are added incrementally to the same well, increasing the concentration of the mitochondrial modulators. The optimal concentrati.......

Discussion

Detailed and correct quantification of oxidative phosphorylation is an indispensable tool when describing the energy states of T cells. The state of mitochondrial fitness can be directly related to T cell activation potential, survival, and differentiation^1,5. With this protocol, it is possible to determine the various properties of oxidative phosphorylation (see Table 4 for a detailed explanation). Precise quantification of these properties of o.......

Materials

Name	Company	Catalog Number	Comments
24-well tissue culture plate	Nunc	142485
Anti-CD3xCD28 beads	Gibco	11161D
Antimycin A	Merck	A8674
Carbonyl cyanide 4-(trifluoromethoxy)-phenylhydrazone (FCCP)	Sigma-Aldrich	C2920
Cell-Tak	Corning	354240	For coating
Dimethyl sulfoxide (DMSO)	Sigma Aldrich	D9170
Human Serum	Sigma Aldrich	H4522	Heat inactivated at 56 °C for 30 min
IL-15	Peprotech	200-02
IL-2	Peprotech	200-15
Lymphoprep	Stemcell Technologies	07801
Oligomycin	Merck	O4876
PBS	Thermo Fisher	10010023
RPMI 1640	Gibco-Thermo Fisher	61870036
Seahorse Calibrant	Agilent Technologies	102416-100
Seahorse XF 1.0 M glucose solution	Agilent Technologies	103577-100
Seahorse XF 100 mM pytuvate solution	Agilent Technologies	103578-100
Seahorse XF 200 mM glutamine solution	Agilent Technologies	103579-100
Seahorse XF RPMI medium, pH7.4	Agilent Technologies	103576-100	XF RPMI media
Seahorse XFe96 Analyser	Agilent Technologies		Flux analyzer
Seahorse XFe96 cell culture microplates	Agilent Technologies	102416-100	XF cell culture plate
Seahorse XFe96 sensor cartridge	Agilent Technologies	102416-100
Sodium Bicarbonate concentrate 0.1 M (NaHCO3)	Sigma Aldrich	36486
Sodium Hydroxide solution 1 N (NaOH)	Sigma Aldrich	S2770-100ML
X-VIVO 15	Lonza	BE02-060F
T cell beads magnet DynaMag-2 Magnet	Thermo Fisher	12321D
Seahorse wave			Flux analyzer software