A type 2 cytokine Fc–IL-4 revitalises exhausted CD8+ T cells against cancer

Current cancer immunotherapy predominately focuses on eliciting type 1 immune responses fighting cancer; however, long-term complete remission remains uncommon. A pivotal question arises whether type 2 immunity can be orchestrated alongside type 1-centric immunotherapy to achieve enduring response against cancer. Here, we show that an interleukin-4 fusion protein (Fc–IL-4), a typical type 2 cytokine, directly acts on CD8+ T cells and enriches functional terminally exhausted CD8+ T (CD8+ TTE) cells in the tumour. Consequently, Fc–IL-4 remarkably enhances anti-tumour efficacy of type 1 immunity-centric adoptive T cell transfer (ACT) or immune checkpoint blockade (ICB) therapies and induces durable remission across multiple syngeneic and xenograft tumour models. Mechanistically, we uncovered that Fc–IL-4 signals through both signal transducer and activator of transcription 6 (STAT6) and mammalian target of rapamycin (mTOR) pathways, augmenting the glycolytic metabolism and nicotinamide adenine dinucleotide (NAD+) level of CD8+ TTE cells in a lactate dehydrogenase A (LDHA)-dependent manner. The metabolic modulation mediated by Fc–IL-4 is indispensable for reinvigorating intratumoural CD8+ TTE cells. These findings underscore Fc–IL-4 as a potent type 2 cytokine-based immunotherapy that synergizes effectively with type 1 immunity to elicit long-lasting responses against cancer. Our study not only sheds light on the synergy between these two types of immune responses but also unveils an innovative strategy for advancing next-generation cancer immunotherapy by integrating type 2 immune factors. Overall design: 1. For the in vivo study, B16F10 tumor-bearing CD45.2+Thy1.2+ C57BL/6 mice received i.v. adoptive transfer of activated Thy1.1+ PMEL CD8+ T cells (5 × 106 per mouse), followed by four doses of peritumoral (p.t.) administration of Fc–IL-4 (20 µg per mouse) or PBS control every other day. After the above treatment, tumors were collected and digested, and tumor-infiltrating PMEL T cells were enriched and sorted out for scRNA-seq. 2. For the in vitro study, single-cell co-profiling of epigenomic landscape and gene expression in the same single nuclei was performed on the ex vivo-induced CD8+ terminally exhausted T cells in the presence or absence of 20ng/mL IL-4.