for medical persons

1. Regulatory T cell
Dr.Biplabendu Talukdar.
MD( IHBT), M.Phil( RMTS), PhD scholar
State Program Officer ,State Blood Cell,WB
Consultant Narayana Hospital

2. Introduction
Regulatory T cells (Tregs) has an indispensable role in
1.Maintaining immunological unresponsiveness to self-antigens and
2. Suppressing excessive immune responses deleterious to the host.
Tregs are produced in the thymus as a functionally mature
subpopulation of T cells and can also be induced from naive T cells in
the periphery.
Recent research reveals the cellular and molecular basis of Treg
development and function and implicates dysregulation of Tregs in
immunological disease

3. Natural Treg are characterised as expressing
both the CD4 T cell co-receptor and CD25,
which is a component of the IL-2 receptor.
Treg are thus CD4+ CD25+.
Expression of the nuclear transcription
factor Forkhead box P3 (FoxP3) is
the defining property which determines
natural Treg development and function.

4. • FoxP3 is crucial for maintaining suppression of the
immune system. Naturally occurring mutations in the
FOXP3 gene can result in self-reactive lymphocytes
that cause a rare but severe disease IPEX (Immune
Dysregulation, Polyendocrinopathy, Enteropathy, X-
Linked) in humans and scurfy in mice.

5. • Tregs suppress activation, proliferation and
cytokine production of CD4+ T cells and
CD8+ T cells, and are thought to suppress
B cells and dendritic cells.
• Tregs can produce soluble messengers
which have a suppressive function,
including TGF-beta, IL-10 and
adenosine.
• Additional markers of natural Tregs are
CD152 (CTLA-4) and GITR
(glucocorticoid-induced TNF receptor),
although it should be noted that these are
also expressed by other T-cell types
periodically (e.g. activated T cells)

6. Development of regulatory T cell
• Haematopoietic cells are identified from human yolk
sac at 18th day of Gestational life .
• No lymphocyte present at yolk sac.
• Para aortic splanchnopleura (PAS) and aorto gonad
mesonephron (AGM) are the next site for
haematopoiesis after 27th day of gestational life.
• Fetal Liver derived precursor haematopoietc and
lymphocytes production beings from 9th week of
gestational life.
• Phenotypically mature T cell identified at 16th to 17th weeks of gestation

7. Continue
• Human thymus beings develop from 4th
week of Intrauterine life and completed
at 9th week.
• Notch signalling molecule is required
for T cell differentiation and proliferation
at thymic gland.
• GATA3, Tcf1, Bcl11b transcription factors are essential for T
lineage specification programme.

8. Cell signalling
• Complex mechanism of
communication for cellular
activities and coordinated cells
action.
Type : 1.Juxtacrine signalling
2. Paracrine Signaling
3.Endocrine Signaling.

9. T cell differentiation
T cell according to activating
stage
Naïve T cell
Activated T cell
Effector T cell
Memory T Cell

10. Course of T cell
• Pro T cell
(CD3-TCR-CD4-CD8-)
• Pre T cell
(CD3+TCRpTα:βCD4+CD8+)
• Immature T cell
(CD3+TCR+CD4+CD8+)
• Mature T cell
(CD3+TCR+CD4+/CD3+TCR+
CD8+)

12. Classification of T cells
60 to 65% cells are
CDn, CD3,CD4 & CDS also known as CD4/TH/T helper cell.
TH cell further classify according to secretion of cytokines
TH1 and TH2 ,
TH1 targeted total intracellular pathogen , ie Bacteria, Parasite.
TH2 helps in antibody production in B cells.
30 t0 35% cell are
CD2,CD3,CD4, CD8 also known as CD8/ Cytotoxic cell
Classify immunological regulator cell as T suppressor or Ts

13. Thymus Derived Treg Cell
• Autoimmune-preventive CD4+ T cells revealed the CD25 molecule
(the IL-2 receptor α chain) as a candidate.
• Removal or reduction of CD25+CD4+ Tregs also provokes effective
tumor immunity in otherwise nonresponding animals and augments
microbial immunity in chronic infection, leading to eradication of
tumors or microbes, respectively (reviewed in Wang and Wang, 2007,
Belkaid and Rouse, 2005).
• Conversely, CD25+CD4+ T cells enriched from normal mice suppress
allergy, establish tolerance to organ grafts, prevent graft-versus-host
disease after bone marrow transplantation, and promote feto-maternal
tolerance (reviewed in Sakaguchi, 2005) .

14. Continue
• . First, the normal immune system generates CD25+CD4+ Tregs that
are engaged in suppressing immune responses toward self, quasi-self
(such as autologous tumor cells), and non-self (such as microbes and
allografts).
• Second, the normal thymus produces potentially pathogenic self-
reactive T cells as well as functionally mature Tregs; mature Tregs
persist in the periphery and exert dominant control over the self-
reactive T cells.
• Third, Treg deficiency in the periphery is sufficient to evoke chronic T
cell-mediated autoimmunity and immunopathology

16. Foxp3 Controls Treg Development and Function
• Naturally occurring Tregs specifically express the
transcription factor Foxp3 (forkhead box P3), a member of
the forkhead/winged-helix family of transcription factors.
Foxp3 is a master regulator of Treg development and
function.
• Mutations of the human gene FOXP3 are the cause of the
genetic disease IPEX (immune dysregulation,
polyendocrinopathy, enteropathy, X-linked syndrome), which
is the human counterpart of Scurfy (reviewed in Ochs et al.,
2005; ).

17. Interleukin 2 Maintains Foxp3+ Tregs
• Interleukin 2 (IL-2) is another molecule critical for the
function of Tregs. The Treg marker CD25 is a component of
the high-affinity IL-2 receptor (IL-2R) and is functionally
essential for Treg development. IL-2 has long been thought to
be a major cytokine for T cell proliferation and differentiation
based on its effects on T cell growth in vitro

18. Factors required for Treg generation
• TCR
• CD28
• Cytokines – IL2
IL15
TGF beta
FoXP3

19. classification of T reg
• Treg further classified according to production of cytokines
1. TH3 ---- produced TGF beta
2. Tr1 ---- produced IL10
3. Tr35 ---- produced IL 35

20. Regulatory T cells (Treg)
are an essential component of the immune system,
balancing necessary aggressiveness against foes
with tolerance for self-constituents
Sakaguchi S. Annu Rev Immunol 2004; 22: 531-562
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY
Tregs
Natural Tregs (FOXP3)
Inducible Tregs
Tr1 (IL10)
Th3 (TGFB1)
Dolganiuc A. J Leuc Biol 2008; 84: 614-622

21. T reg cell generation
• T reg cell generated from two sources
*From Thymus known as natural T cell( nTreg)
*From periphery known as peripheral Inducible Treg cell
( iTreg/pTreg)

22. Peripheral Generation of T regs from Naive T Cells
• in vitro antigenic stimulation of naive T cells in the presence of TGF-β
In TGF-β-dependent in vitro Treg induction,
• IL-6 hampers the differentiation of naive T cells to Foxp3+ cells
• TGF-β stimulation in the presence of IL-6 facilitates T cell
differentiation to Th17 cells in mice.
• IL-2 facilitates the differentiation of naive CD4+ T cells into Foxp3+
Tregs but inhibits their differentiation into Th17 cells.
• Additionally, retinoic acid, which is secreted by a particular subset of
dendritic cells in the gut-associated lymphoid tissue, inhibits IL-6-
driven induction of Th17 cells.
• In the presence of TGF-β, retinoic acid facilitates the differentiation of
naive T cells to Foxp3+

23. Function of T reg cells
• Anti-inflammatory cytokines
• Reduced availability to IL2 via absorption of CD25
• Lysed other immune effector cells by granzyme
secretion.
• Modulate activation state and function of APC and
other immune effector cells.
• Release suppressor factor such as Galectin 1

24. Regulatory T cells
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY

25. Mechanism of action
• Inhibition of immunoregulatory cytokines TGF beta, IL 10,
IL35
• Inhibition of Cytolysis of effector cells by producing
Granzyme and perforine
• Metabolic interruption by decreasing of IL2 and cAMP
through A2 adenosine receptor
• Interaction with dendritic cells that modulate the function.

28. Tregs: A Clinical Perspective

29. 29
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY
Acute, Chronic Infection, Tissue Injury
Medzhitov R. Nature 2008; 454: 428-435

30. 30
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY
Introduction
Medzhitov R. Nature 2008; 454: 428-435

31. Tissue repair

32. Regulatory T cells
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY

33. Infection and Liver disease

34. Apoptosis and Liver
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY

35. Regulatory T cells- Foes?
 Positive correlation between the HBV DNA level and the frequency of
Tregs in the blood of chronically infected patients
 Accumulation of Tregs in the liver of patients with chronic HBV
infection
 Presence of CD4+FOXP3+ T cells in the liver of chronically HCV infected
persons Scott et al, 2007
Stoop et al, 2007
Franzese et al, 2005
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY
Autoimmune Hepatic Diseases
 Reduced levels of circulating CD4+CD25high
Tregs
 Reduced levels in correlation with higher
disease activity or poorer prognosis
Longhi et al, 2004
Longhi et al, 2004; Boyer et al, 2004
Chronic Hepatic Infection

36. Transplantation
Establish tolerance to
organ grafts, prevent
graft-versus-host
disease after bone
marrow
transplantation

37. Pregnancy

38. Factors help in Foetomaternal tolerance
• 1.Expression of Non Classical HLA from trophoblasic cell.
• 2. IDO expression by placental cell , depletion of tryptophan
and produce kyuneurine.
• FasL production from trophoblastic tissue.
• Complement regulatory protein expression by trophoblastic
tissue.

39. Autoimmunity

40. • Depletion of naturally arising Tregs elicits autoimmunity but also augments
immune responses to non-self-antigens.
• Treg depletion produces inflammatory bowel disease, which likely results
from excessive immune responses to commensal bacteria in the intestine
• Removal or reduction of CD25+CD4+ Tregs also provokes effective tumor
immunity in otherwise nonresponding animals and augments microbial
immunity in chronic infection, leading to eradication of tumors or microbes,
respectively.
• Conversely, CD25+CD4+ T cells enriched from normal mice suppress
allergy,
• establish tolerance to organ grafts, prevent graft-versus-host disease after
bone marrow transplantation, and promote feto-maternal tolerance.

41. • Autoimmunity ensues when central and/or peripheral tolerance
barriers are overcome thereby allowing the activation of self-
reactive T cells, which induce tissue destruction . : (a)
Tregnumbers are reduced and/or Tregs are dysfunctional due to
inherent deficiencies in autoimmune susceptible individuals, (b)
Treg suppressive function is inhibited, diverted or converted by the
chronic inflammation that occurs in autoimmunity, and/or (c)
self-reactive effector T cells (Teff) become unusually aggressive
and are refractory to regulation by otherwise functional
Tregs because they either overwhelm regulatory control or express
molecules that render them resistan

42. Kim et al, Nature Immunol 2007;8: 191-197
 CD4+CD25+Foxp3 regulatory T Cells protect against T Cell-mediated
fulminant hepatitis in a TGF-β-dependent manner in mice Wei et al, 2008
Regulatory T cells- or Friends?
DEPARTMENT OF IMMUNOLOGY & HISTOCOMPATIBILITY – UNIVERSITY OF THESSALY

43. Cancer cell

44. • Removal or reduction of CD25+CD4+ Tregs also
provokes effective tumor immunity in otherwise
nonresponding animals and augments microbial
immunity in chronic infection, leading to eradication
of tumors or microbes, respectively.

45. Summary
*Natural Treg are characterised as expressing both the CD4 T cell
co-receptor and CD25, which is a component of the IL-2 receptor.
* T reg develop outside the thymus in the periphery from naïve
Tcell , known as peripheral / inducible T reg cell.
* T regulatory cell develop in vitro culture helps in adaptive
immunity.
* Regulatory T cells having immune regulatory activity that is
helpful for the control in infection and autoimmunity, prevention
of carcinogenesis and engraftment of embryo in utero.
* Therapeutic application of in vitro cultred T reg cell may be
helpful for the treatment of immunogenic diseases.

46. Thank you
For your
pacence