LILRB3 (ILT5) is a myeloid cell checkpoint that elicits profound immunomodulation
Muchaala Yeboah, Charys Papagregoriou, Des C. Jones, H.T. Claude Chan, Guangan Hu, Justine S. McPartlan, Torbjörn Schiött, Ulrika Mattson, C. Ian Mockridge, Ulla-Carin Tornberg, Björn Hambe, Anne Ljungars, Mikael Mattsson, Ivo Tews, Martin J. Glennie, Stephen M. Thirdborough, John Trowsdale, Björn Frendeus, Jianzhu Chen, Mark S. Cragg, Ali Roghanian
Muchaala Yeboah, Charys Papagregoriou, Des C. Jones, H.T. Claude Chan, Guangan Hu, Justine S. McPartlan, Torbjörn Schiött, Ulrika Mattson, C. Ian Mockridge, Ulla-Carin Tornberg, Björn Hambe, Anne Ljungars, Mikael Mattsson, Ivo Tews, Martin J. Glennie, Stephen M. Thirdborough, John Trowsdale, Björn Frendeus, Jianzhu Chen, Mark S. Cragg, Ali Roghanian
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Research Article Immunology

LILRB3 (ILT5) is a myeloid cell checkpoint that elicits profound immunomodulation

Abstract

Despite advances in identifying the key immunoregulatory roles of many of the human leukocyte immunoglobulin-like receptor (LILR) family members, the function of the inhibitory molecule LILRB3 (ILT5, CD85a, LIR3) remains unclear. Studies indicate a predominant myeloid expression; however, high homology within the LILR family and a relative paucity of reagents have hindered progress toward identifying the function of this receptor. To investigate its function and potential immunomodulatory capacity, a panel of LILRB3-specific monoclonal antibodies (mAbs) was generated. LILRB3-specific mAbs bound to discrete epitopes in Ig-like domain 2 or 4. LILRB3 ligation on primary human monocytes by an agonistic mAb resulted in phenotypic and functional changes, leading to potent inhibition of immune responses in vitro, including significant reduction in T cell proliferation. Importantly, agonizing LILRB3 in humanized mice induced tolerance and permitted efficient engraftment of allogeneic cells. Our findings reveal powerful immunosuppressive functions of LILRB3 and identify it as an important myeloid checkpoint receptor.

Authors

Muchaala Yeboah, Charys Papagregoriou, Des C. Jones, H.T. Claude Chan, Guangan Hu, Justine S. McPartlan, Torbjörn Schiött, Ulrika Mattson, C. Ian Mockridge, Ulla-Carin Tornberg, Björn Hambe, Anne Ljungars, Mikael Mattsson, Ivo Tews, Martin J. Glennie, Stephen M. Thirdborough, John Trowsdale, Björn Frendeus, Jianzhu Chen, Mark S. Cragg, Ali Roghanian

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Figure 2

Characterization of LILRB3 antibodies.

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Characterization of LILRB3 antibodies. (A) LILRB3 mAb affinity assessed ...
(A) LILRB3 mAb affinity assessed by SPR. LILRB3-hFc recombinant protein was immobilized, and various LILRB3 mAbs flowed across the chip. Representative LILRB3 clone A16 shown. (B) LILRB3 domain epitope mapping. HEK293F cells transfected with WT LILRB3 (full-length extracellular portion), D1–3, D1–2, or D1 were stained with LILRB3 clones, followed by an anti-hIgG secondary antibody. Schematic of domain constructs and restriction digest of each DNA construct shown (top panel). Histograms showing staining of 2 representative clones differentially binding to color-coded cells expressing WT (D4), D1–3, D1–2, and D1 (bottom panel; n = 3 independent experiments). (C) Ability of generated mAbs to cross-block binding of a commercial LILRB3 mAb (clone 222821). PBMCs were stained with unconjugated LILRB3 antibody clones and subsequently stained with a directly conjugated 222821 mAb and analyzed by flow cytometry; representative clones displayed (A1 nonblocking; A12 partial blocking), as indicated. (D) LILRB3 2B4 reporter cells were incubated with 10 μg/mL LILRB3 antibodies overnight to assess receptor signaling potential as judged by GFP induction measured by flow cytometry; representative clones with percentage of GFP expression shown (n = 2 independent experiments).