Engagement of MHC class I by the inhibitory receptor LILRB1 suppresses macrophages and is a target of cancer immunotherapy

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Exciting progress in the field of cancer immunotherapy has renewed the urgency of the need for basic studies of immunoregulation in both adaptive cell lineages and innate cell lineages. Here we found a central role for major histocompatibility complex (MHC) class I in controlling the phagocytic function of macrophages. Our results demonstrated that expression of the common MHC class I component β2-microglobulin (β2M) by cancer cells directly protected them from phagocytosis. We further showed that this protection was mediated by the inhibitory receptor LILRB1, whose expression was upregulated on the surface of macrophages, including tumor-associated macrophages. Disruption of either MHC class I or LILRB1 potentiated phagocytosis of tumor cells both in vitro and in vivo, which defines the MHC class I–LILRB1 signaling axis as an important regulator of the effector function of innate immune cells, a potential biomarker for therapeutic response to agents directed against the signal-regulatory protein CD47 and a potential target of anti-cancer immunotherapy.

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We thank the members of the Weissman laboratory and the Stanford Stem Cell Center community for discussion and assistance; J.P. Volkmer, R. Majeti, K. Loh, N. Fernhoff, M. McCracken and J. Zee for input and advice; T. Storm, T. Naik, A. McCarty, F. Khameneh, J. Ho and P. Lovelace for logistical support; and G. Krampitz (Stanford University) for the APL1 cell line. Supported by the D.K. Ludwig Fund for Cancer Research (NIH R01CA086017 and NIHG R01GM100315 to I.L.W.), the Cancer Research Institute (Irvington Fellowship to R.L.M.), the Human Frontier Science Program Organization (postdoctoral fellowship to B.R.), the NIH (hematology training grant T32 HL120824-03 to B.R.), the University of Wisconsin Medical Scientists Training Program (GM008692 to L.J.B.), the National Research Service Award 1F30DK108561, the Paul and Daisy Soros Fellowship for New Americans (to J.M.T.) and the Stanford Medical Scientist Training Program (NIH GM07365 to A.A.B., K.W., A.M.R., J.M.T., B.M.G. and J.Y.C.).

Author information

Author notes

    • Roy L. Maute

    Present address: Ab Initio Biotherapeutics, South San Francisco, CA, USA

  1. Amira A. Barkal, Kipp Weiskopf, Irving L. Weissman and Roy L. Maute contributed equally to this work.


  1. Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA

    • Amira A. Barkal
    • , Kipp Weiskopf
    • , Kevin S. Kao
    • , Sydney R. Gordon
    • , Benyamin Rosental
    • , Ying Y. Yiu
    • , Benson M. George
    • , Maxim Markovic
    • , Nan G. Ring
    • , Jonathan M. Tsai
    • , Kelly M. McKenna
    • , Po Yi Ho
    • , Robin Z. Cheng
    • , James Y. Chen
    • , Irving L. Weissman
    •  & Roy L. Maute
  2. Brigham and Women’s Hospital, Boston, MA, USA

    • Kipp Weiskopf
  3. Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA

    • Layla J. Barkal
  4. Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA

    • Aaron M. Ring
  5. Ludwig Center for Cancer Stem Cell Research and Medicine, Stanford, CA, USA

    • Irving L. Weissman
  6. Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA, USA

    • Irving L. Weissman
  7. Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA

    • Irving L. Weissman


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A.A.B., K.W., I.L.W. and R.L.M. wrote the manuscript; A.A.B., K.W., A.M.R., I.L.W. and R.L.M. conceived of and designed all experiments; K.W. and R.L.M. performed LegendScreen analysis of tumor cell lines; K.S.K., S.R.G., B.M.G. and R.Z.C. assisted with mouse experiments; B.R. and Y.Y.Y. performed receptor-Fc staining experiments; M.M. assisted with tumor measurements and injections and provided sample preparation for primary human macrophages; N.G.R. generated human macrophages and tested the in vitro growth kinetics of DLD1 sublines; J.M.T. performed histology and immunofluorescence staining; K.M.M. generated NSG macrophages; K.M.M., P.Y.H. and R.L.M. tested CD47 expression in tumor cell lines; J.Y.C. assisted with generating knockout cell lines; L.J.B. assisted with statistical analysis; A.M.R. generated Fab fragments of W6/32; and I.L.W. supervised the research and edited the manuscript.

Competing interests

K.W., A.M.R., I.L.W. and R.L.M. and are co-inventors on patent application PCT/US2015/057233, which is related to this work, and own stock of FortySeven, which is pursing clinical approval of antibody Hu5F9-G4, directed against human CD47.

Corresponding authors

Correspondence to Irving L. Weissman or Roy L. Maute.

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