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

tel-00827710, version 1 - 29 May 2013
Overall, my project aimed to expand upon the newly described tetramer-based enrichment
strategy in order to study parameters influencing the outcome of CD8 + T cell responses. We
specifically chose to examine our hypotheses in the context of a well-characterized model of
cross-presentation as this pathway is known to be crucial for eliciting robust CD8 + T cell
response and has already been targeted for purposes of vaccination.
Specifically, our experimental model of cross-presentation was designed as follows: live, H-
2K bm1 splenocytes expressing a membrane-bound Ovalbumin (K bm1 mOva splenocytes) were
injected into recipient mice. The SIINFEKL peptide is known to be the immunodominant
peptide originating from the Ovalbumin protein and is presented on the MHC-I molecule H-
2K b . Consequently, the CD8 + T cell response directed against Ovalbumin was followed over
time by using the MHC-I-peptide ‘K b -SIINFEKL’ tetramer. The naïve precursor frequency of
T cells interacting with K b -SIINFEKL complexe was determined by tetramer-based
enrichment: between 100 and 200 specific CD8 + T cells can be found in naïve mice.
Compared to other epitopes from several antigens that have been studied, this represents a
rather low frequency, as the number of epitope-specific T cells for a given antigen can vary
from 50 to 1000 cells in naïve mice (Obar et al., 2008).
Importantly, in this model of antigen, the expression of the H-2K bm1 molecule, which contains
a mutation that inhibits direct peptide presentation, ensures that all CD8 + T cell responses
were induced by cross-presentation (Figure 15).
Figure 15. Model of cross-presentation.
Interestingly, despite the expression of a mutated K b molecule by the injected splenocytes,
this MHC molecule K bm1 can still be detected by the anti-K b antibody (clone AF6-88.5)
(Figure 16A). However, this mutation no longer allows for the binding and presentation of
the Ovalbumin-derived SIINFEKL peptide on K bm1 molecule (Figure 16B). While β2m -/-
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