TGF-ß broadly modifies rather than specifically suppresses reactivated memory CD8 T cells in a dose-dependent manner (ATAC-Seq)
Transforming growth factor ß (TGF-ß) directly acts on naïve, effector and memory T cells to control cell fate decisions, which was shown using genetic abrogation of TGF-ß signaling. TGF-ß availability is altered by infections and cancer, however the dose-dependent effects of TGF-ß on memory CD8 T cell (Tmem) reactivation are still poorly defined. We examined how activation and TGF-ß signals interact to shape the functional outcome of Tmem reactivation. We found that TGF-ß could suppress cytotoxicity in a manner that was inversely proportional to the strength of the activating TCR or pro-inflammatory signals. In contrast, even high doses of TGF-ß had a comparatively modest effect on IFN-? expression in the context of weak and strong reactivation signals. Since CD8 Tmem may not always receive TGF-ß signals concurrently with reactivation, we also explored whether the temporal order of reactivation versus TGF-ß signals is of importance. We found that exposure to TGF-ß prior to as well as after an activation event were both sufficient to reduce cytotoxic effector function. Concurrent ATAC-seq and RNA-seq analysis revealed that TGF-ß altered ~10% of the regulatory elements induced by reactivation and also elicited transcriptional changes indicative of broadly modulated functional properties. We confirmed some changes on the protein level and found that TGF-ß-induced expression of CCR8 was inversely proportional to the strength of the reactivating TCR signal. Together, our data suggest that TGF-ß is not simply suppressing CD8 Tmem, but modifies functional and chemotactic properties in context of their reactivation signals and in a dose-dependent manner. Overall design: OT-1 memory mice were harvested for secondary lymphoid organs (lymph nodes and spleen). A T cell isolation was performed to isolate T cells. T cells were plated for 2 hours with or without TGFb and for 24 hours with SIINFEKL and TGFb or SIINFEKL alone. OT-1 cells (CD45.1 and CD8+) were FACS sorted for downstream analysis by bulk RNAseq and bulk ATACseq.