Central memory T (T CM ) cells patrol lymph nodes and perform conventional memory responses upon re-stimulation: proliferation, migration, and differentiation into diverse T cell subsets while also self-renewing. Resident memory T (T RM ) cells are parked within single organs, share properties with terminal effectors, and contribute to rapid host protection. We observed that reactivated T RM cells rejoined the circulating pool. Epigenetic analyses revealed that T RM cells align closely with conventional memory T cell populations, bearing little resemblance to recently activated effectors. Fully differentiated T RM cells isolated from small intestine epithelium exhibited the potential to differentiate into T CM , T EM , and T RM cells upon recall. Ex-T RM cells, former intestinal T RM that rejoined the circulating pool, heritably maintained a predilection for homing back to their tissue of origin upon subsequent reactivation and a heightened capacity to re-differentiate into T RM cells. Thus, T RM cells can rejoin the circulation but are advantaged to re-form local T RM when called upon.

Abdelsamed et al. demonstrate that the poised effector potential of human memory CD8 T cells is coupled to maintenance of effector-associated DNA methylation programs during in vitro and in vivo homeostatic proliferation.

DNMT3A deletion preserves CAR T cell functionality during prolonged stimulation.

The pool of beta cell-specific CD8 + T-cells in type 1 diabetes (T1D) sustains an autoreactive potential despite having access to a constant source of antigen. To investigate the long-lived nature of these cells, we established a DNA methylation-based T cell “multipotency index” and found that beta cell-specific CD8 + T-cells retained a stem-like epigenetic multipotency score. Single cell ATAC-seq analysis confirmed the co-existence of naive and effector-associated epigenetic programs in individual beta cell-specific CD8 + T-cells. Assessment of beta cell-specific CD8 + T-cell anatomical distribution and the establishment of stem-associated epigenetic programs revealed that self-reactive CD8 + T-cells isolated from murine lymphoid tissue retained developmentally plastic phenotypic and epigenetic profiles relative to the same cells isolated from the pancreas. Collectively, these data provide new insight into the longevity of beta cell-specific CD8 + T cell responses, and document the utility of this novel methylation-based multipotency index for investigating human and mouse CD8 + T-cell differentiation.

Highlights d CD19-CAR T cells undergo extensive DNA methylation reprogramming during therapy d DNA methylation status of the CAR T cell product can predict in vivo expansion d CD8 + CD19-CAR T cells acquire exhaustion-associated DNA methylation programs d Antigen-positive tumor relapse does not elicit CAR T cell expansion

No abstract

Memory CD8 T cells have a unique ability to provide lifelong immunity against pathogens containing their cognate epitope. Because of their ability to provide lifelong protection, the generation of memory T cells is now a major focus for current vaccination or adoptive cell therapy approaches to treat chronic viral infections and cancer. It is now clear that maintenance of memory CD8 T cells occurs through a process of antigen-independent homeostatic proliferation, which is regulated in part by the gamma chain cytokines IL-7 and IL-15. Here, we will describe the role of these cytokines in the survival and self-renewal of memory CD8 T cells. Further, we will describe the role of epigenetics in the maintenance of acquired functions among memory CD8 T cells during homeostatic proliferation.

Chimeric antigen receptor T cell (CAR-T cell) therapeutic efficacy is associated with long-term T cell persistence and acquisition of memory. Memory subset formation requires TCF-1, a master transcription factor for which few regulators have been identified. Here, we demonstrate using an immune-competent mouse model of B cell acute lymphoblastic leukemia (B-ALL) that Regnase-1 deficiency promotes TCF-1 expression to enhance CAR-T cell expansion and memory-like cell formation. This leads to improved CAR-T-mediated tumor clearance, sustained remissions, and protection against secondary tumor challenge. Phenotypic, transcriptional, and epigenetic profiling identified increased tumor-dependent programming of Regnase-1-deficient CAR-T cells into TCF-1+ precursor exhausted (TPEX) cells characterized by upregulation of both memory and exhaustion markers. Regnase-1 directly targets Tcf7 mRNA; its deficiency augments TCF-1 expression leading to the formation of TPEX that support long-term CAR-T cell persistence and function. Regnase-1 deficiency also reduces exhaustion and enhances the activity of TCF-1- CAR-T cells. We further validate these findings in human CAR-T cells, where Regnase-1 deficiency mediates enhanced tumor clearance in a xenograft B-ALL model. This is associated with increased persistence and expansion of a TCF-1+ CAR-T cell population. Our findings demonstrate pivotal roles of TPEX, Regnase-1, and TCF-1 in mediating CAR-T cell persistence and recall responses, and identify Regnase-1 as a modulator of human CAR-T cell longevity and potency that may be manipulated for improved therapeutic efficacy.