RESEARCH ARTICLE SUMMARY
◥IMMUNOLOGY
Butyrophilin 2A1 is essential for phosphoantigen
reactivity bygdT cells
Marc Rigau, Simone Ostrouska, Thomas S. Fulford, Darryl N. Johnson, Katherine Woods,
Zheng Ruan, Hamish E.G. McWilliam, Christopher Hudson, Candani Tutuka, Adam K. Wheatley,
Stephen J. Kent, Jose A. Villadangos, Bhupinder Pal, Christian Kurts, Jason Simmonds,
Matthias Pelzing, Andrew D. Nash, Andrew Hammet, Anne M. Verhagen, Gino Vairo,
Eugene Maraskovsky, Con Panousis, Nicholas A. Gherardin, Jonathan Cebon, Dale I. Godfrey†,
Andreas Behren†,AdamP.Uldrich*†
INTRODUCTION:T cells represent a key compo-
nent of the immune system that can recog-
nize foreign molecules (antigens) via cognate
cell surface receptors termed T cell recep-
tors (TCRs). The two main families of T cells,
known asabandgdTcells,aredefinedby
the different gene loci that they use to gener-
ate their respective TCRs.abT cells typically
recognize antigens displayed on the surface
of target cells in association with antigen-
presenting molecules known as major histo-
compatibility complex(MHC) molecules. Much
less is known about howgdT cells recog-
nize antigen, although it is clear they are also
essential to protective immunity. In humans,
manygdTcells(classifiedasVg9Vd2 T cells)
respond to small phosphorylated nonpep-
tide antigens, called phosphoantigens (pAgs),
which are produced by cellular pathogens and
cancers. In turn,gdT cells become activated,
proliferate, rapidly produce proinflammatory
cytokines such as IFN-g, and exert cytotoxic
activity. pAg recognition appears to involve
a cell surface molecule, butyrophilin 3A1
(BTN3A1), which plays a necessary, but not
sufficient, role in this process. Therefore, the
molecular basis that underpins pAg recogni-
tion by Vg9Vd2 T cells remains unclear and
represents a long-standing conundrum, which
has impeded the study of these important
immune cells.RATIONALE:In contrast toabT cells, Vg9Vd 2
T cells are not MHC-restricted and can recog-
nize pAg expressed by multiple cancers and
infectious diseases. Thus, they represent an
attractive target for the development of new
immunotherapy treatments. A much clearerunderstanding of the molecular basis for pAg
recognition is required to optimally harness
these cells for immunotherapy. We undertook
a multipronged approach to investigate which
molecules are necessary for pAg detection
bygdTcells.Weusedagenome-widescreento
identify molecules that mediate pAg-driven
gdT cell activation. Furthermore, we asked if
these molecules directly bind to the Vg9Vd 2
TCR and how they work in conjunction with
BTN3A1.RESULTS:The top candidate molecule iden-
tified in our genome-wide screen was butyr-
ophilin 2A1 (BTN2A1), a molecule distinct
from, but related to, BTN3A1. We show that
without BTN2A1, Vg9Vd2Tcellscannotbe
activated by either bacterial or mammalian
pAgs, and that BTN2A1 expression was re-
quired for Vg9Vd2Tcell–
mediated tumor cell killing.
NeitherBTN3A1northe
other butyrophilin family
members tested can com-
pensate for loss of BTN2A1.
BTN2A1 can bind directly
to the Vg9Vd2 TCR and associates closely with
BTN3A1 on the surface of target cells. We also
identify an important role for the transmem-
brane and/or intracellular domain of BTN2A1.
Furthermore, pAg-mediated activation ofgdT
cells requires coexpression of both BTN2A1
and BTN3A1, which together appear to convey
pAg recognition and responsiveness by Vg9Vd 2
T cells. Lastly, we show that BTN2A1 binds to
the side of the Vg9 domain of the TCR, and also
reveal the existence of a critical putative second
ligand-binding domain on a separate region of
the TCR that incorporates Vd2. Disruption of
either of these binding sites abrogated the
ability of Vg9Vd2 T cells to respond to pAg.CONCLUSION:Our findings suggest thatgd
T cells recognize pAg in an entirely different
way to how any other immune cell recognizes
antigen. We propose a model whereby BTN2A1
and BTN3A1 co-bind the Vg9Vd2TCRinre-
sponse to pAg. This pAg likely modifies the
BTN2A1–BTN3A1 complex to make it stimu-
latory, which may occur through BTN molecule
remodeling and/or conformational changes.
Targeting these molecules will create new op-
portunities for the development ofgdTcell–
based immunotherapies for diseases in which
pAgs are produced, including infections, auto-
immunity, and cancer.▪RESEARCH
Rigauet al.,Science 367 , 642 (2020) 7 February 2020 1of1
The list of author affiliations is available in the full article online.
*These authors contributed equally to this work.
†Corresponding author. Email: [email protected]
(A.P.U.); [email protected] (A.B.); godfrey@
unimelb.edu.au (D.I.G.)
Cite this article as M. Rigauet al.,Science 367 , eaay5516
(2020). DOI: 10.1126/science.aay5516ActivationTumor cellBTN3A1?Infected cell or
Ag-presenting cellBTN3A1
?BacteriaParasiteForeign
phosphoantigenSelf phosphoantigen
Phosphoantigen-driven immune response:
Cytokine production, cell killingVb 2 Vb^2Va 9 Va^9ab T cellab TCR ab TCRBTN2A1 BTN2A1Butyrophilin 2A1 plays a critical role in phosphoantigen recognition by human T cells.
HumangdT cells become activated in response to microbial and cancer-derived phosphoantigens,
but the molecular mechanism for phosphoantigen recognition remained unclear. We show that
a critical component of this recognition is the cell-surface molecule butyrophilin 2A1 (BTN2A1),
which binds to thegdTCR and in conjunction with BTN3A1, signals the presence of
phosphoantigens togdT cells.
ON OUR WEBSITE◥Read the full article
at http://dx.doi.
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science.aay5516
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