TIM-4 Glycoprotein-Mediated Degradation of Dying Tumor Cells by Autophagy Leads to Reduced Antigen Presentation and Increased Immune Tolerance

Phagocytosis of apoptotic cells by myeloid cells has been implicated in the maintenance of immune homeostasis. In this study, we found that T cell immunoglobulin-and mucin domain-containing molecule-4 (TIM-4) repressed tumor-specific immunity triggered by chemotherapy-induced tumor cell death. TIM-4 was found to be highly expressed on tumor-associated myeloid cells such as macrophages (TAMs) and dendritic cells (TADCs) and danger-associated molecular patterns (DAMPs) released from chemotherapy-damaged tumor cells induced TIM-4 on tumor-associated myeloid cells recruited from bone marrow-derived precursors. TIM-4 directly interacted with AMPK alpha 1 and activated autophagy-mediated degradation of ingested tumors, leading to reduced antigen presentation and impaired CTL responses. Consistently, blockade of the TIM-4-AMPK alpha 1-autophagy pathway augmented the antitumor effect of chemotherapeutics by enhancing tumor-specific CTL responses. Our finding provides insight into the immune tolerance mediated by phagocytosis of dying cells, and targeting of the TIM-4-AMPK alpha 1 interaction constitutes a unique strategy for augmenting antitumor immunity and improving cancer chemotherapy.