Voie d'immunisation et séquence d'administration de l ... - TEL

tel-00827710, version 1 - 29 May 2013
regulated at the level of antigen engulfment When adjuvant is delivered prior to antigen
uptake, it induces DC maturation and death (Figure 53A). Yet, if antigen has already been
engulfed, poly I:C may activate the DC differently, inducing, for instance, a different survival
program, enhanced persistence of antigen inside the DC, or longer interactions with antigen-
specific T cells (Figure 53B, hypothesis 2).
Differentiating between these two hypotheses is difficult to address in vivo because, while
many DCs will sense poly I:C, only few of them will phagocytose antigen (Figure 44). In
order to address this on a per cell basis, the aim would be to develop an in vitro model that
could compare DCs sensing only poly I:C and DCs that detect both antigen and poly I:C. In
order to do this, bone-marrow-derived DCs could be cultivated with Flt3-ligand to obtain
CD8α + -like DCs. Liposomes containing phosphatidylserine may be used to mimic dying
cells. In this way, we could be able to identify and compare the adjuvant treated versus
adjuvant + antigen treated populations of DCs by looking at their maturation state, or doing
RNA expression analysis to study regulation of cell survival genes. The transcription factors
STAT would be viable targets for analysis, as the STAT molecules responsible for
transmitting type I IFN signaling have already been shown to differ depending on the DC
maturation state (Longman et al., 2007).
3) Poly I:C versus type I IFN effects
In our model, we used poly I:C as a type I IFN-inducer. We investigated the specific effects
of type I IFN by using IFNAR -/- and IRF3/7 DKO mice as recipients, as well as IFNAR -/- OT-
I responding T cells. However, we cannot exclude a concurrent effect of poly I:C on the
cellular targets.
(a) Cross-talk between TLR3 and type I IFN pathways
CD8α + DCs are the only DC subset that expresses TLR3. We observed a disappearance of
these cells upon poly I:C injection. Interestingly, Hasan and colleagues studied the survival of
human DCs after treatment with several different TLR ligands: TLR3 ligands that signal
through TRIF, TLR5 ligands signaling through Myd88 and TLR4 ligands that can signal
through both pathways. They showed that TLR5 ligands induced DC survival, while
treatment with TRL3 or TLR4 ligands, poly I:C and LPS respectively, trigerred DC death.
Importantly, DC survival was restored if the type I IFN pathway was blocked by anti-IFNAR
neutralizing antibodies (Hasan et al., 2007). These results demonstrated that TLR signaling
can impact the DC life cycle depending on which intracellular pathway is engaged and that
this phenomenon can be modulated by type I IFN.
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