1. Academic Validation
  2. SLAMF3 and SLAMF4 are immune checkpoints that constrain macrophage phagocytosis of hematopoietic tumors

SLAMF3 and SLAMF4 are immune checkpoints that constrain macrophage phagocytosis of hematopoietic tumors

  • Sci Immunol. 2022 Jan 21;7(67):eabj5501. doi: 10.1126/sciimmunol.abj5501.
Dan Li 1 Wei Xiong 1 Yuande Wang 1 Jin Feng 1 Yuexi He 1 Juan Du 2 Jing Wang 3 Meixiang Yang 4 Hui Zeng 2 Yong-Guang Yang 5 Ning Wu 6 Shasha Chen 7 Zhongjun Dong 1 8
Affiliations

Affiliations

  • 1 School of Medicine and Institute for Immunology, Beijing Key Lab for Immunological Research on Chronic Diseases, Tsinghua University, Beijing 100084, China.
  • 2 Beijing Key Laboratory of Emerging Infectious Diseases, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China.
  • 3 Shanghai Institute of Immunology, Department of Immunology and Microbiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
  • 4 Biomedical Translational Research Institute, Jinan University, Guangzhou 510632, China.
  • 5 First Bethune Hospital and International Center of Future Science, Jilin University, Changchun 130061, China.
  • 6 Department of Immunology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
  • 7 Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
  • 8 School of Basic Medicine, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan 271016, China.
Abstract

The interaction of SIRPα with CD47 represents a major mechanism for preventing macrophage phagocytosis. However, CD47-independent mechanisms are poorly defined. Here, we report a critical role of SLAM family receptors (SFRs), ubiquitously expressed on hematopoietic cells and forming homotypic interactions, in constraining macrophage phagocytosis. We found that SFR deficiency triggered macrophage phagocytosis of hematopoietic cells, leading to severe rejection of donor hematopoietic graft in recipient mice. Specific SFR members, mainly SLAMF3 and SLAMF4, were identified as "don't eat me" receptors on macrophages. These receptors inhibited "eat me" signals, such as LRP1-mediated activation of mTOR and Syk, through SH2 domain-containing phosphatases. SFRs combined with, but were independent of, CD47 to mitigate macrophage phagocytosis, and the combined deletion of SFRs and CD47 resulted in hematopoietic cytopenia in mice. This SFR-mediated tolerance was compromised in patients with hemophagocytic lymphohistiocytosis, a syndrome characterized by inappropriate phagocytosis toward hematopoietic cells. Loss of SFRs potently elicited macrophage rejection of hematopoietic tumors. Deletion of SFRs also significantly enhanced the phagocytosis of CD19-positive hematopoietic targets by the macrophages expressing the chimeric CD19 antigen receptor. Therefore, SFR-mediated inhibition of macrophage phagocytosis is critical to hematopoietic homeostasis, and SFRs may represent previously unknown targets for tumor immunotherapy.

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