CD4⁺ Th Cell-Derived Extracellular Vesicles Orchestrate CD8⁺ T Cells and Eosinophils to Enhance Anti-Tumor Immunity

CD4⁺ T cells play a pivotal role in anti-tumor immunity by assisting CD8⁺ T cells in eliminating MHC I⁺ tumor cells and promoting immune responses against MHC-deficient tumors through myeloid-cell recruitment. Extracellular vesicles (EVs) are increasingly recognized as important mediators of intercellular immune communication; however, how CD4⁺ T helper (Th)-derived EVs modulate tumor immune cells, including CD8⁺ T cells and eosinophils, to orchestrate anti-tumor responses remains poorly understood. Here, we show that immune checkpoint molecules, including PD-1 and TIM-3, and the cytokine IL-5 are enriched on CD4⁺ Th cell microvilli and EVs. Activated CD4⁺ Th cells released both exosomes and ectosomes, which cooperatively suppressed tumor progression through two complementary mechanisms. First, CD4⁺ Th-derived exosomes and ectosomes displayed immune checkpoint receptors such as PD-1 and TIM-3 on their surface, thereby intercepting tumor-derived inhibitory signals, reversing T cell exhaustion, and enhancing cytotoxic T cell activity. Second, CD4⁺ Th-derived EVs carried IL-5 and other effector molecules that promoted JAK-STAT signaling, eosinophil recruitment to tumor sites, and eosinophil-mediated tumor cell killing through degranulation. Moreover, CD4⁺ Th-derived EVs remodeled the tumor microenvironment by enhancing CD8⁺ T cell and eosinophil infiltration and activation, suggesting their potential role in immune regulation and cancer therapy.