Abstract

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.