Mapping the role of ITK (interleukin 2 inducible T cell kinase) and TCR (T cell receptor) signal strength in determining the early fate of CD8 T cells using Nr4a3 “timed” fluorescent reporter

Abstract

ITK plays a key role in the rate and magnitude of TCR-dependent transcription factor activity and early genetic programming that determines the extent of CD8 T cell effector and memory function. To study the extent of this role we crossed an OT1 transgenic ITK germline KO to the Nr4a3-Tocky timer model which produces a time dependent fluorescent reporter. Nr4a3 is highly expressed following TCR activation and thus is a good metric for TCR signal strength and duration. The Tocky protein fluoresces blue, at λ 466 and then, after ~7hrs, degrades to a red fluorescence at λ 583. OT-1 Rag1KO ITK (WT, +/-, and -/-) Nr4a3-Tocky bulk splenocytes were stimulated with the altered peptide ligand T4 Ova peptide at varying concentrations for 12/24 hours and sorted on Tocky+ Blue/Red and negative events. ITK -/- CD8s showed elevated CD69 and CD25 but were variable for Tocky expression. Both Tocky Negative and Tocky Blue sorted ITK -/- CD69+ CD8s expressed higher IRF8, cFos, cMyc, Bcl2, and TCF1/7 as well as lower IRF4 versus WT at 12 hours post-stimulation. Analyses of Tocky Blue/Red or persistently active CD8s showed WT having increased expression of TCF1 and similar expression of IRF8, cFos, Bcl2, Eomes and Egr2 compared to ITK -/-. Bcl2 and PDL1 are also highly expressed through all stages of TCR signaling in ITK -/- CD8s. These data indicate that differences in TCR signal strength with and without ITK can affect the time at which transcriptional networks arise after TCR stimulation.