TGF-b/TIF1g signaling restrains CD8+ T cell expansion while preserving cytotoxic competence

TIF1g (TRIM33) sets a TGF-β signal threshold in CD8+ T cells, and its loss enables robust expansion but markedly reduces Granzyme B and Perforin under TGF-β signaling.

• Why it matters: TGF-β can both restrain and shape CD8+ T cell responses, but the molecular switch that separates activation/proliferation from cytotoxic differentiation is unclear.
• What they did: The authors used TIF1g-deficient CD8+ T cells to map transcriptional and effector changes under TGF-β, then tested cytotoxic control in a secondary Listeria monocytogenes challenge and in lymphopenic homeostatic proliferation.
• The result: In vivo, TIF1g-deficient CD8+ T cells expanded strongly yet failed to efficiently control Listeria monocytogenes due to impaired cytotoxic activity, and TIF1g loss accelerated B16 melanoma growth with reduced Perforin in tumor-infiltrating CD8+ T cells.

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