TGF-β broadly modifies rather than specifically suppresses reactivated memory CD8 T cells in a dose-dependent manner

Abstract

Transforming growth factor {beta} (TGF-{beta}) directly acts on naive, effector and memory T cells to control cell fate decisions, which was shown using genetic abrogation of TGF-{beta} signaling. TGF-{beta} availability is altered by infections and cancer, however the dose-dependent effects of TGF-{beta} on memory CD8 T cell (Tmem) reactivation are still poorly defined. We examined how activation and TGF-{beta} signals interact to shape the functional outcome of Tmem reactivation. We found that TGF-{beta} 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-{beta} had a comparatively modest effect on IFN-{gamma} expression in the context of weak and strong reactivation signals. Since CD8 Tmem may not always receive TGF-{beta} signals concurrently with reactivation, we also explored whether the temporal order of reactivation versus TGF-{beta} signals is of importance. We found that exposure to TGF-{beta} 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-{beta} 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-{beta}-induced expression of CCR8 was inversely proportional to the strength of the reactivating TCR signal. Together, our data suggest that TGF-{beta} is not simply suppressing CD8 Tmem, but modifies functional and chemotactic properties in context of their reactivation signals and in a dose-dependent manner.