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Volume 3 Supplement 2

30th Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2015)

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Fas expression in memory CD8+ T cell subsets augments cellular differentiation and effector function

Memory CD8+ T cells (TMem) have the capacity to provide lifelong host protection against intracellular pathogens and cancer. Despite phenotypic and functional heterogeneity among TMem, the expression of Fas — a tumor necrosis family receptor (TNFR) superfamily member conventionally known as a death receptor — is held in common among all TMem subsets across multiple species. As Fas has been shown to mediate non-death signaling in other cell types, we set out to elucidate the role of Fas signaling in defined TMem subsets, including T stem cell memory (TSCM), T central memory (TCM), and T effector memory (TEM). We found that augmenting Fas signaling in stimulated TSCM using an oligomerized form of its ligand FasL resulted in augmented cellular differentiation and a loss in IL-2 secretion capacity. Conversely, antibody blockade (anti-FasL) of Fas signaling in TCM retarded cellular differentiation both phenotypically and functionally. To genetically disentangle the pro-apoptotic and differentiation signals from Fas, we made use of a mutant Fas lacking a transmembrane cysteine residue (FasC194V) that is unable to undergo S-palmitoylation and aggregate efficiently in lipid rafts. Using transgenic mice expressing this C194V Fas construct on a Fas-deficient lpr background, we found that FasC194V TMem can still undergo cellular differentiation in the absence of death signaling. In vivo, TMem expanded with anti-FasL showed greater expansion, on-target immunity and withheld differentiation. Additionally, in a relevant syngeneic model of current human T cell immunotherapy, TMem cells expanded with anti-FasL and genetically engineered with an anti-CD19 chimeric antigen receptor (CAR) exhibited enhanced CAR expression, reduced differentiation, and augmented anti-lymphoma activity compared to controls. These studies demonstrate that Fas signaling promotes not only cell death but also TMem effector differentiation, a finding that has implications for the design and execution of T cell-based immunotherapies in patients with cancer or infectious disease.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Yamamoto, T., Leonardi, A., Liu, H. et al. Fas expression in memory CD8+ T cell subsets augments cellular differentiation and effector function. j. immunotherapy cancer 3 (Suppl 2), P329 (2015). https://doi.org/10.1186/2051-1426-3-S2-P329

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  • DOI: https://doi.org/10.1186/2051-1426-3-S2-P329

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