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International Congress of Immunology 2016
Abstract Book
barrier to the development of specific mechanistic models.
Both extracellular and intracellular structural transitions have
been implicated in TCR “triggering,” but little is known about
whether specific structures within the transmembrane (TM)
regions of the receptor complex are required to support the
coupling of these events through the lipid bilayer. We have
recently shown that the TCRαβ TM domains form a closely
associated coiled-coil interface that provides a structured core
for the TCRαβ-CD3δε-CD3γε-ζζ complex in the membrane. This
interface is mediated by a network of inter-helical hydrogen
bonds between TM sequences that are absolutely conserved
across vertebrate evolution and in both αβ and γδ forms of the
TCR. Receptors with mutations at the key polar residues were
expressed normally but exhibited a severe defect in antigen-
triggered IL-2 production. These data support a model in which
extracellular alterations propagate through the structured TCR/
CD3 TM domains to initiate intracellular signalling and provide a
structural rationale for the ability of T cells to respond to a single
antigenic peptide:MHC ligand through a receptor-intrinsic
conformational mechanism.
2782
Quantitative analysis of Vav1 signalosome in primary CD4 T
cells identify several newVav1 partners including CD226
Gaud, G.
1
, Roncagalli, R.
2
, Gonzalez De Pedro, A.
3
, Malissen, B.
2
,
SAOUDI, A.
1
1
INSERM U 1043, CNRS UMR 5282, Toulouse, France,
2
CIML,
Marseille, France,
3
IPBS, Toulouse, France
A tightly controlled balance of immune cell signaling is
necessary for proper immunity. A dysfunction of this balance
has been observed in several immune mediated diseases. Vav1
is a signaling molecule involved in T cell development and
functions. Recently, our team showed that Vav1 is involved
in several auto-immune diseases such has multiple sclerosis
and myasthenia gravis. However, the molecular mechanisms
by which Vav1 controls these phenotypes are still poorly
understood.
In the present study, we analyzed the composition and dynamic
of Vav1 signalosome in primary CD4
T cells by generating a novel animal model where Vav1 was
tagged at its C-terminus withOneStrepTag (Vav1OST). Following
in vitro
stimulation of primary CD4T lymphocytes, Vav1 was pull-
down at different time-points, and its interactome was analyzed
by mass spectrometry, allowing the characterization of Vav1
interactors and their binding kinetics following stimulation. This
approached allow us to describe the first spatial and temporal
vav1 interactome and to identify numerous new Vav1 partners.
We analyzed the major biological processes of these interactors
and as expected most of them are involved in TCR signaling.
This proteomic study also leads us to identify 4 co-receptors
involved in immunological synapse formation. Among them,
CD226 is involved in CD4 T cell proliferation and differentiation.
We demonstrate here for the first time that Vav1 is a crucial
effector of CD226 signaling in CD4T cells.
3964
Engagement of TCR with foreign and self antigens trigger
distinct signaling pathways to generate different T cell
responses
Shiokawa, M.
1
, Ishikawa, E.
1
, Ogata, M.
2
, Saito, T.
3
, Yamasaki, S.
1
1
Division of Molecular Immunology, Medical Institute of
Bioregulation, Kyushu University, Fukuoka, Japan,
2
Department of
Biochemistry and Proteomics, Mie University Graduate School of
Medicine, Tsu, Japan,
3
Laboratory for Cell Signaling, RIKEN Center
for IMS, Yokohama, Japan
Mature T cells are activated by recognizing foreign antigens
(Ags) through T cell receptor (TCR). Although it was widely
believed that endogenous self Ags do not activate mature T
cells, recent studies have demonstrated that they can induce T
cell maintenance in the periphery. However, it remains unclear
how these distinct responses are generated through the same
receptor. To address this issue, we compared the contribution
of Erk, a pivotal MAP kinase for cell growth and survival, to
these distinct responses. By establishing mature T cell-specific
Erk1/2-deficient mice, we found that mature T cells could
survive in the periphery without Erk. Moreover, homeostatic T
cell proliferation was observed in the absence of Erk, suggesting
that Erk is not essential for T cell maintenance induced by self
Ags. In contrast, OVA-specific responses, such as proliferation
or cytokines production, were abrogated by loss of Erk. Thus,
T cell responses induced by self/foreign Ags are regulated
differentially, at least concerning the requirement of Erk. Next, to
examine the correlation of peptide affinity and Erk dependency,
OT-I TCR Tg T cells transferred into TAP-deficient mice were
stimulated with peptides with different affinities and examined
T cell responses. High-affinity peptide SIINFEKL could induce
vigorous proliferation
in vivo
, whereas low-affinity peptides
induced survival without proliferation. Again, we found that
the former response was largely dependent on Erk. Collectively,
these results suggest that the strength of TCR signal may be
determine different mature T cell responses through distinct
signaling pathways.
Autoimmunity 1
2907
Rogue germinal center B cells: unconventional lymphocytes
released by FAS inactivation that drive IgE and
autoantibody production
Butt, D.
1
, Chan, T.
1
, Bourne, K.
1
, Hermes, J.
1
, Strasser, A.
2
, Tangye, S.
1
,
Phan, T.
1
, Rao, V.K.
3
, Brink, R.
1
1
Garvan Institute of Medical Research, Sydney, Australia,
2
The
Walter and Eliza Hall Institute of Medical Research, Melbourne,
Australia,
3
National Institute of Allergy and Infectious Diseases,
NIH, Bethesda, United States
The mechanistic links between genetic variation and
autoantibody production in autoimmune disease remain
obscure. Inactivating mutations in the death receptor FAS
or its ligand (FASL) cause Autoimmune Lymphoproliferative
Syndrome (ALPS) and lupus-like autoimmune diseases. FAS
is thought to safeguard against autoantibody production by