CD28 Costimulation of T Helper 1 Cells Enhances Cytokine Release In Vivo.

Daniela Langenhorst,Thomas Hünig,Bernard Vanhove,Stephanie Haack,Anna Uri,Niklas Beyersdorf,Fred Lühder,Selina Göb

doi:10.3389/fimmu.2018.01060

Abstract

Compared to naive T cells, differentiated T cells are thought to be less dependent on CD28 costimulation for full activation. To revisit the role of CD28 costimulation in mouse T cell recall responses, we adoptively transferred in vitro generated OT-II T helper (Th) 1 cells into C57BL/6 mice (Thy1.2+) and then either blocked CD28–ligand interactions with Fab fragments of the anti-CD28 monoclonal antibody (mAb) E18 or deleted CD28 expression using inducible CD28 knock-out OT-II mice as T cell donors. After injection of ovalbumin protein in adjuvant into the recipient mice we observed that systemic interferon (IFN)γ release strongly depended on CD28 costimulation of the Th1 cells, while secondary clonal expansion was not reduced in the absence of CD28 costimulation. For human memory CD4+ T cell responses we also noted that cytokine release was reduced upon inhibition of CD28 costimulation. Together, our data highlight the so far underestimated role of CD28 costimulation for the reactivation of fully differentiated CD4+ T cells.

Highlights

For full activation, naive T cells require at least two signals: signal one originating from the interaction of the T cell receptor (TCR) with peptide/major histocompatibility complexes and the second signal stemming from the interaction of CD28 with its ligands CD86 and CD80 on antigen-presenting cells (APCs) [1]
As our data obtained with mouse OT-II T cells indicated that CD28 costimulation enhanced interferon γ (IFNγ) secretion by restimulated T helper 1 (Th1) cells, we studied cytokine secretion by human peripheral blood mononuclear cells (PBMC) upon addition of T cell recall antigens in vitro
Blocking CD28–B7 ligand interactions (Figure 1C, left graphs) or tamoxifen-induced CD28 deletion (Figure 1C, right graphs), clearly diminished IFNγ concentrations in the serum. This observation is in line with the known enhanced IFNγ expression during primary effector T cell responses after release of IFNγ mRNA from glyceraldehyde-3-hosphate dehydrogenase (GAPDH) upon induction of glycolysis [19], which itself is driven by CD28 costimulation [20]

Summary

Introduction

Naive T cells require at least two signals: signal one originating from the interaction of the T cell receptor (TCR) with peptide/major histocompatibility complexes and the second signal stemming from the interaction of CD28 with its ligands CD86 and CD80 on antigen-presenting cells (APCs) [1]. Binding of CTLA-4-Ig to the T cells, which express CD86 and CD80 themselves [4], and induction of indoleamine 2,3-dioxygenase (IDO) expression in APCs [5] hamper the interpretation of these data Another recent and elegant study addressed the role of CD28 in effector/ memory CD4+ T cell responses by using OX40-Cre floxed CD28 mice leading to CD28 deletion after initial antigen recognition, i.e., within the first 48 h of the primary immune response in vivo [6]. We set up our study to analyze the contribution of CD28 costimulation during antigenic recall responses of already differentiated mouse Th1 cells To this end, we first differentiated ovalbumin (OVA) peptide-specific TCR-transgenic OT-II T cells into Th1 cells in vitro before adoptive transfer in vivo and induction of genetic deletion of CD28 or antibody-mediated blocking of the interaction of CD28 with its ligands. As both mouse and human polarized CD4+ Th cells have been shown to undergo reprogramming under certain conditions in vitro and in vivo [7,8,9], we followed the impact of CD28 costimulation on Th cell lineage stability

Methods

Results

Conclusion