The Ikaros Transcription Factor Regulates Responsiveness to IL-12 and Expression of IL-2 Receptor Alpha in Mature, Activated CD8 T Cells

Eric T Clambey,Philippa Marrack,John W Kappler,Bernard Collins,Mary H Young,Jens Eberlein,Alexandria David,Ryan M Teague

doi:10.1371/journal.pone.0057435

Abstract

The Ikaros family of transcription factors is critical for normal T cell development while limiting malignant transformation. Mature CD8 T cells express multiple Ikaros family members, yet little is known about their function in this context. To test the functions of this gene family, we used retroviral transduction to express a naturally occurring, dominant negative (DN) isoform of Ikaros in activated CD8 T cells. Notably, expression of DN Ikaros profoundly enhanced the competitive advantage of activated CD8 T cells cultured in IL-12, such that by 6 days of culture, DN Ikaros-transduced cells were 100-fold more abundant than control cells. Expression of a DN isoform of Helios, a related Ikaros-family transcription factor, conferred a similar advantage to transduced cells in IL-12. While DN Ikaros-transduced cells had higher expression of the IL-2 receptor alpha chain, DN Ikaros-transduced cells achieved their competitive advantage through an IL-2 independent mechanism. Finally, the competitive advantage of DN Ikaros-transduced cells was manifested in vivo, following adoptive transfer of transduced cells. These data identify the Ikaros family of transcription factors as regulators of cytokine responsiveness in activated CD8 T cells, and suggest a role for this family in influencing effector and memory CD8 T cell differentiation.

Highlights

CD8 T cells control primary and secondary infections by multiple pathogens [1]
While future studies will be required to investigate Ikaros family mRNA splicing and protein expression in CD8 T cells, these data demonstrate that mature CD8 T cells express Ikaros family members, and suggest that the Ikaros family may influence CD8 T cell function
Differentiation Cues Given the expression of multiple Ikaros family members within mature CD8 T cells, and the known genetic redundancy within these gene products, we sought to investigate the contribution of the Ikaros gene family to the properties of mature CD8 T cells

Summary

Introduction

CD8 T cells control primary and secondary infections by multiple pathogens [1]. Following T cell activation, CD8 T cells acquire multiple effector functions, including cytokine production, cytolytic activity, and the capacity to become long-lived CD8 memory T cells. The founding member of this family, functions to activate and repress transcription, and plays a central role in hematopoietic development, lineage decisions and as a tumor suppressor [3]. These transcription factors have a high degree of conservation in both their N-terminal DNA-binding zinc fingers and C-terminal dimerization zinc fingers [4]. Occurring dominant negative variants can be generated by alternative splicing, and can be detected in healthy cells at low levels [6], and in malignancies where Ikaros-family loss of function is thought to be critical for progression to malignancy [7]

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Results

Conclusion