International Congress of Immunology 2016
the former more susceptible to signal-deprived apoptotic cell
death. Thus, small molecules that can selectively deplete eTreg
cells via exploiting Treg-specific functions are instrumental in
augmenting anti-tumor immunity in various cancers.
Pharmacological inhibition of acid sphingomyelinase or
genetic ablation enhances CD4
regulatory T cell
, Reuter, D.
, Werner, S.
, Avota, E.
, Müller, N.
, Kleuser, B.
, Becker, K.A.
, Gulbins, E.
, Schneider-Schaulies, J.
University of Wuerzburg, Institute for Virology and
Immunobiology, Wuerzburg, Germany,
University of Potsdam,
Institute of Nutritional Science, Nuthetal, Germany,
Duisburg-Essen, Institute for Molecular Biology, Essen, Germany
The acid sphingomyelinase (human: ASM, mouse: Asm)
hydrolyses sphingomyelin into phosphocholine and ceramide
which generates signalling platforms and affects viral
regulatory T (Treg) cells depend on
CD28 signalling for their survival and function, a receptor that
has previously been shown to activate the Asm/ASM. In line
with these findings we observed that Treg cells of wild-type (wt)
mice displayed higher basal and CD28-induced Asm activity
and, thus, contained more ceramide than conventional CD4
(Tconv) cells. Investigating Asm-deficient mice we could show
that the frequency of Treg cells among CD4
T cells is increased
and their suppressive activity is enhanced compared to wt
mice - at least partially due to a higher turnover of the effector
molecule CTLA-4. Similar to anti-CD28 antibody-mediated
expansion of Treg cells in wt mice, these changes in Treg cell
frequencies and/ or function in the Asm-deficient mice were
associated with more infected neurons using a CNS infection
model with recombinant measles virus. Of clinical importance,
pharmacological inhibition of Asm in mouse splenocytes
and in mice
led to higher frequencies of Treg cells among
T cells, as did ASM inhibition in primary human peripheral
blood mononuclear cells (PBMC). ASM inhibitors should, thus,
be considered as potential immunomodulatory agents for the
therapy of inflammatory and autoimmune disorders. This study
was supported by a grant from the DFG (FOR2123/P02).
TCR signal strength regulates Akt substrate specificity to
induce alternate Th and Treg differentiation programs
, Hawse, W.F.
, Sheehan, R.P.
, Boggess, W.C.
University of Pittsburgh, Immunology, Pittsburgh, United States,
University of Pittsburgh, Computational and Sysems Biology,
Pittsburgh, United States,
UnIversity of Notre Dame, Notre Dame,
T regulatory (Treg) cells are induced following stimulation of
naïve CD4 T cells with low dose antigen to an extent that is
negatively correlated with signaling via the Akt/mTOR pathway.
Strong TCR signals induce high levels of Akt activity that inhibit
development of Treg by poorly understood mechanisms. Here,
we show that high dose stimulation of T cells results in the
phosphorylationof Akt on two regulatory sites, Serine (S) 473and
Threonine (T) 308, whereas low dose stimulation results in only
T308 phosphorylation. Mathematical modeling shows that the
dual phosphorylation of Akt on S473 and T308 is controlled by
a feedback loop involving PTEN, mTORC2 and the transcription
factor FoxO1 that creates a sharp activation threshold with
respect to antigen dose and stimulus duration. Using mass
spectrometry to analyze phosphorylated Akt substrates at
different levels of stimulation, we find profound differences
in the substrates phosphorylated, suggesting that a switch in
substrate specificity coupled to the phosphorylation status
of Akt may lead to alternative cell fates. Proteins differentially
phosphorylated by these two states of Akt include RNA splicing
factors, and we find changes in the splice variant expression
levels of key TCR signaling proteins, such as CD3ζ and CD45 that
correlate with the observed differences in cell fate. Knockdown
of specific splicing factors changed the ratios of Th versus Treg
cells induced. Together, this work demonstrates that alternative
splicing can affect the outcome of T cell fate decisions and
identifies alternate Akt-mediated signaling networks that drive
T cell differentiation.
Evaluation of Galectin-9 blocking mono-clonal antibodies
as novel immune-checkpoint inhibitors via the targeting of
regulatory T cells in cancer
, Mrizak, D.
, Renaud, S.
, Barjeon, C.
, de Launoit, Y.
, Moralès, O.
, Busson, P.
, Delhem, N.
CNRS, UMR 8161, Institut de Biologie de Lille, Lille, France,
Université Paris-sud, CNRS UMR 8126 and Institut Gustave Roussy,
The immune system has the potential to recognize and
eliminate cancer cells but is held back by certain inhibitory
pathways. Regulatory T cells (Tregs) are key players in these
pathways. They are a subpopulation of T lymphocytes whose
role is to inhibit the immune response in order to maintain
immunological homeostasis. However, the Treg population is
often upregulated in cancer patients where it promotes tumor.
This has made Tregs an appealing target for immunotherapeutic
approaches such as anti-CTLA-4 and anti-PD-1. Galectin-9
(Gal-9) a b-galactoside binding lectin has been described as
an immunosuppressive molecule which is expressed by both
cancer cells and Tregs in order to suppress the anti-tumoral
immune response. In this study we first aimed to confirm the role
of Gal-9 in Treg-mediated-immuno-suppression. Then we tested
the effects of Gal-9 blocking on Treg function and subsequently
the anti-tumoral immune response. Following Treg isolation
from healthy donors, we have proven via QPCR, ELISA and
flow cytometry that Gal-9 is highly expressed and secreted by
Tregs with respect to conventional T cells. Moreover, the anti-
Gal-9 antibody significantly inhibited the immuno-suppressive
function of Tregs in mixed leukocyte reaction proliferation tests.
We have also demonstrated that Gal-9 blocking in PBMC culture
promotes the secretion of Th1 cytokines TNF-a and IFN-g.
Finally, we successfully used the anti-Gal-9 antibody to inhibit