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

tel-00827710, version 1 - 29 May 2013
multiparameter flow cytometry and intracellular staining, or large genomic screening allow
for the analysis of an increased number of defined parameters with which characterize
antigen-specific T cells. Historically, IFNγ is the most studied cytokine secreted by T cells as
it has been shown to have an important role in the clearance of several infections. Tumor
Necrosis Factor (TNF) that has also been extensively surveyed due to its implication in the
killing of various pathogens. Finally, IL-2 is often measured in experimental systems due to
its known role in inducing the proliferation of T cells through both an autocrine and paracrine
manner, as well as its role in promoting memory T cell differentiation. Combining the
analysis of these three cytokines allows for a more precise characterization of the T cell
population under examination. Additionally, the expression of granzyme and perforin can be
analyzed to study the cytolytic ability of T cells. Secretion of chemokines can also be assessed
and may reflect the role of the T cell in the orchestration of the inflammatory response.
Interestingly the presence of multifunctional T cells has been correlated to a better protection
against infection (Almeida et al., 2007; Darrah et al., 2007). Specifically, the simultaneous
production of IFNγ and TNFα by the same T cell has been shown to result in the enhanced
killing of Leishmania major as compared to T cells that only produce one of these cytokines
(Bogdan et al., 1990). The fact that multifunctional T cells are associated with a better
response can be explained both by their ability to combine several functions, as well as the
fact that polyfunctional T cells also secrete more cytokines on a per-cell basis, highlighted by
the higher median fluorescent intensity (MFI) of this population (Seder et al., 2008).
(b) When does diversification occur?
A first approach taken to address the question of the timing of T cell diversification was to
follow the development of a T cell response starting from a single naïve T cell. Initially,
Stemberger and colleagues adoptively transferred a single naïve OT-I T cell and showed that
the different subsets of effector and memory cells can be obtained from this single cell
(Stemberger et al., 2007). Another group obtain similar results using a biological bar-coding
system, which makes each T cell clone traceable in vivo (Gerlach et al., 2010). Together,
these data support a model of progressive diversification starting from just a few cells that
differentiate into various effector cells, which lose their ability to convert into memory cells
over time. In contrast, another study suggests that the CD8 T cell clonal heterogeneity could
be induced at the first cell division. The formation of the immunological synapse between the
DC and the engaged T cell generates an asymmetry in the location of protein degradation
machinery, resulting in different amounts of the transcription factor T-bet passed along to the
two daughter cells, leading to differential functional evolution in that generation (Chang et al.,
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