Download Inducing and expanding regulatory T cell populations by foreign

Inducing and expanding regulatory T cell
populations by foreign antigen
Karsten Kretschmer
NATURE IMMUNOLOGY 2005; 6:1219
Background



The extrathymic generation and proliferation of regulatory
T cells may contribute to self-tolerance as well as the poor
immunogenicity of tumors and may be exploited clinically
to prevent or reverse unwanted immunity.
The contributions of thymically and extrathymically
generated suppressor T cells to the peripheral pool of
CD4+CD25+ suppressor T cells is not known.
The ability to generate de novo in secondary lymphoid
tissue represent an important tool in the induction of
antigen-specific tolerance in the fully mature immune
system. Also, this pathway of generating suppressor cells
may be used by tumors to avoid tumor-specific immune
responses.





CD4+CD25+ regulatory T cells expressing the lineage
marker Foxp3
The cellular and molecular mechanisms involved in the
peripheral generation of CD4+CD25+ suppressor T cells
are not known
recombination activating gene 2–deficient (Rag2–/–)
Thy-1.2 BALB/c Rag2–/– TCR-HA mice and Thy-1.1
BALB/c congenic Rag2–/– TCR-HA mice express a TCR
specific for H-2IEd HA
Antigens can be targeted to DCs in vivo by means of the
DEC-205 endocytosis receptor
Objection


As the exact cellular and molecular mechanisms
involved in the peripheral generation of
CD4+CD25+ suppressor T cells are not known,
we investigated whether this process can be
initiated through antigen presentation by
dendritic cells (DCs).
This seemed an important issue to study, as crosspresentation of tumor-specific antigens by major
histocompatibility complex class II molecules on
DCs could constitute an essential pathway by
which tumor cells induce Foxp3-expressing
suppressor T cells.
Question

What conditions are suited for the induction of
antigen-specific Foxp3+CD4+CD25+ suppressor
T cells in the context of a fully mature immune
system using anti-DEC–HA?
1.Conversion of naive CD4+CD25– T
cells into CD4+CD25+ T cells.
90% or more of the CD25+
cells were stained with the
clonotypic 6.5 TCR antibody
single-dose injection of
anti-DEC–HA resulted in
little TCR internalization
Question


Does CD4+CD25+ T cells express the Foxp3
which is the marker of T regulatory cells?
Does the converted Foxp3+CD25+ T cells
have regulatory function?
2. Foxp3 expression and antigen-specific
suppression by CD4+CD25+ T cells
Question
What conditions are favoring for suppressor
cell generation?
Antigen dose?
DC activation?
Cell division?
Routes of antigen administration?
3. Efficient induction of CD4+CD25+ regulatory T
cells requires low doses of anti-DEC–HA and lack of
costimulation.
Injection of either a substantial amount of anti-DEC–HA or injection
together of minute amounts of anti-DEC–HA plus anti-CD40 did not
result in efficient and long-lasting conversion of CD4+CD25– naive
T cells into Foxp3+CD4+CD25+ suppressor T cells
4. Inverse relationship of cell division and
CD25 expression.
converted suppressor T cell populations
generated in subimmunogenic conditions
could subsequently be expanded by
delivering antigen in immunogenic
conditions



Different routes of administration of anti-DEC–HA
(intraperitoneal, intravenous and subcutaneous) were
similarly efficient in CD25+ suppressor T cell induction
(data not shown).
Also, prolonged subcutaneous infusion of small amounts of
anti-DEC–HA (10 ng/d for 14 d) by means of osmotic minipumps did not increase the absolute numbers of induced
Foxp3+CD4+CD25+ suppressor T cells (data not shown).
Furthermore, injection of less than 40 ng anti-DEC–HA
resulted in a much reduced recovery of initially seeded T
cells 14 d after injection (data not shown).
Background


TGF-beta could help the conversion of in vitro–stimulated
peripheral CD4+CD25– T cells into suppressor cells
suggests that TGF-b signaling could be involved in the
antigen-driven conversion of suppressor cells in vivo.
Consistent with that idea, mice deficient in components of
the TGF-beta–TGF-beta receptor system have reduced
numbers of peripheral CD4+CD25+ T cells
Question

The role of TGF-beta in antigen
induced T regulator cells generation?
5.Impaired TGF-betaR signaling diminishes
conversion of naive T cells into CD4+CD25+
regulatory T cells.
Conclusion

TGF-beta receptor signaling–dependent
inhibition of proliferation correlated with more
efficient in vivo conversion of naive T cells
into CD4+CD25+ regulatory T cells.
Q: whether increased TGF-b receptor
signaling could reduce proliferation and
enhance anti-DEC–HA–mediated
conversion in vivo?
6.Costimulation of naive CD4+CD25– T cells in
vitro by TCR and TGF-beta receptor.
In vitro, TGF-b1 slightly
inhibited anti-CD3- and
anti-CD28-mediated T cell
proliferation at 36 and 60 h
of culture
Foxp3 mRNA expression
was induced in vitro only
when cells were stimulated
with TGF-b1 plus anti-CD3
and anti-CD28
cells stimulated with TGFb1 plus anti-CD3 and antiCD28 expressed Foxp3
protein 36 h after
stimulation, and this
increased to 23% at day 3.
Foxp3 expression
correlated with CD25
surface expression
7. In vivo conversion of naive CD4+CD25– T
cells costimulated in vitro with TCR and TGFbeta.
Background

IL-2 is a cytokine that controls proliferation of
antigenically stimulated T cells.
Q: whether IL-2 interfered with or enhanced the
conversion of naive T cells into CD4+CD25+
suppressor T cells??
8.Efficient conversion of Il2–/–CD4+CD25–
naive T cells into regulatory T cells.
lack of autocrine IL-2 reduced
proliferation mediated by antiDEC–HA
converted Il-2–/–CD4+6.5+
T cells proliferated in
antigen-draining lymph
nodes after immunization
with peptide in IFA
Conclusion




Conversion was achieved by minute antigen doses
with suboptimal dendritic cell activation.
The addition of transforming growth factor-b or the
absence of interleukin 2 production, which reduces
proliferation, enhanced the conversion rate.
regulatory T cell populations induced in
subimmunogenic conditions could be expanded by
delivery of antigen in immunogenic conditions.
The extrathymic generation and proliferation of
regulatory T cells may contribute to self-tolerance as
well as the poor immunogenicity of tumors and may
be exploited clinically to prevent or reverse unwanted
immunity.