1. Th17 and Treg in RA Seong Wook Kang Division of Rheumatology
Department of Internal Medicine
Chnungnam National University School of Medicine

2. Rheumatoid Arthritis (RA)
A symmetric polyarticular arthritis
Primarily affects the small joints of the hands and feet
Inflammation in the synovium
Pannus invades and destroys local articular structures

3. Role of T cells in RA Prominent T-cell infiltrate in RA synovium
Genetic similarities between RA patients
specific human leukocyte antigen (HLA)-DR genes - HLA DR4, DR14 and DR1
Shared epitope
the third hypervariable region of DR β chains, especially amino acids 70 through 74

4. HLA Class II Molecule

5. Maturation of lymphocytes

6. Routes of antigen entry

7. Activation of naive and effector T cells by antigen
from thymus

8. Phases of T cell responses
Activated T cells deliver signals back to the APCs,
further enhancing their ability to activate T cells
Phases of T cell responses

9. SIGNALS FOR T LYMPHOCYTE ACTIVATION
Proliferation of T lymphocytes and differentiation into effector and memory cells require
Antigen recognition
Costimulation
Cytokines that are produced by the T cells themselves and by APCs and other cells

10. Differentiation of CD4+ T Cells into TH1, TH2, and TH17 Effector Cells

11. Old versus new models of Th cell development

12. Th17 cells
A novel lineage of CD4+ effector T helper (Th) cells which produce IL-17
Murine models of autoimmunity: experimental autoimmune encephalomyelitis (EAE) and collagen-induced arthritis (CIA)
Mediated by Th1 response (?): ablated by Ab for IL-12p40
IL-23 shares with IL-12p40
IL-12: p40 and p35
IL-23: p40 and p19
IL-23, not IL-12 is critically linked to autoimmunity in these models
IL-23 polarized cells express genes associated chronic inflammation, such as IL-17A, IL-17F, IL-6, TNF-a, and proinflammatory chemokines

13. Differentiation of Th17 cells

14. Main activities attributed to Th17 cells

15. Diseases associated with Th17

16. Possible role of Th17 cells in RA
IL-17 and IL-23p19 were found in sera, synovial fluid, and synovial biopsies of most patients with RA
Increased expression of CC chemokine ligand 20 in the inflamed joints of patients with RA
CCL20 : able to bind CCR6 expressing Th17 cells
Increased number of Th17 cells were observed in the peripheral blood and the SF of RA patients

17. Role of Th17 cells in RA

18. Helper T cell (Th) subgroups

19. Autoimmunity and Tolerance
Breakdown of self-tolerance: autoimmune disease
T cell compartment of the immune system can react with a variety of antigens
Equipped with receptors that are able to interact with self–antigens
Auto-reactive T cell: potentially dangerous by initiating autoimmune responses
Protective immune responses need to be stopped or down-regulated
When the body-invading agent has been neutralized
Intensity or chronicity may become dangerous for the body
Regulatory mechanisms are required
Thymic clonal deletion: apoptotic cell death (central tolerance)
Induction of anergy: functional inactivation
Activation-induced cell death
Suppression by regulatory lymphocytes: Role of FOXP3+ regulatory T cells (Treg)

20. T cells suppressing immune responses
Described early 1970s by Gershon and Kondo
In mid-1990s, Sakaguchi identified a subset of CD4+ CD25+ T cells critical for preventing autoimmunity
CD4+ T cells depleted of CD25+ T cells from normal mice, when transferred into syngeneic athymic nude mice induced multiorgan autoimmune disease
Prevented by co-transfer of CD4+ CD25+ T cells
Sakaguchi S. J Immunol 1995

21. Discovery of FOXP3 FOXP3 (forkhead family transcription factor)
A critical regulator of Treg development, function, and homeostasis
FOXP3+ T cells, most of which are CD4+ CD25+
suppress activation, proliferation and effector functions of immune cells including CD4+ and CD8+ T cells, NK cells, NKT cells, B cells and APCs
central in the prevention of autoimmune disease, allergy, and maintenance of allograft tolerance

22. FOXP3+ regulatory T cells in human immune system
Treg expressing FOXP3 are indispensable for the maintenance of self tolerance and immune homeostasis
Genetic mutations in FOXP3 develop a severe, fatal systemic autoimmune disorder
IPEX (Immune dysregulation Polyendocrinopathy Enteropathy X-linked) syndrome
Enlargement of lymphoid organ, insulin-dependent diabetes, eczema, food allergy and concomitant infection

23. Regulatory T cells
Many cell types have been shown to possess the capacity to regulate immune responses
CD4+CD25high regulatory T cells (“Tregs”), CD4+ Tr1 cells, CD4+ Th3 cells, CD8+CD28− T cells, CD4−CD8− T cells and NKT cells

24. Characteristics of regulatory T cells

25. Natural regulatory T cells (nTreg) vs. Induced Treg (iTreg)
Natural regulatory T cells (nTreg): Thymic-derived
One of the best-characterized subsets of immune regulatory cells is the CD4+CD25+/high Tregs
FOXP3 appears to have emerged as the definitive marker for such Tregs
Induced Treg (iTreg)
More recent studies have shown that FOXP3 may also be induced in CD4+FOXP3– T cells in vivo during some immune responses

26. Thymic and Peripheral Generation of FOXP3+ Treg Cells

27. Mechanisms of FOXP3+ Treg cell mediated suppression (direct)

28. Mechanisms of FOXP3+ Treg cell mediated suppression (indirect)

29. Tregs in autoimmune diseases
No difference in the frequency of CD4+ CD25+ Tregs but reduced suppressive activity
Multiple sclerosis
Myasthenia gravis
Type 1 diabetes
Rheumatoid arthritis
Decrease in CD4+ CD25+ Tregs frequency in peripheral blood
SLE
Kawasaki disease
Autoimmune lymphoproliferative syndrome

30. Tregs in human RA
Tregs in patients with RA appear to be present in normal numbers and to exhibit all of the features of Tregs, not only in phenotype but also in their suppression of T cell proliferation.
Circulating Tregs isolated from patients with active RA are unable to suppress the release of pro-inflammatory cytokines by activated T cells and monocytes
Reversal of Treg-suppressive defect by successful anti-TNF treatment

31. Tregs and inflammation in RA
The frequency of Tregs was much greater in the synovial fluid than in peripheral blood
The inflammatory milieu increases the number of Treg cells in the inflamed joint, but impairs their function
TNFα in SF of RA abrogate the suppressive activity of CD4+CD25+ Tregs
Balance between Tregs and pathogenic Th17 cells at the site of inflammation
TGFβ and IL-6 secretion in rheumatoid synovium

32. Reciprocal generation of Treg and Th17 cells

33. Tregs can convert to Th17 cells
Treg and Th17 cells may differentiate from the same precursor T cells
The balance of TGFβ and IL-6 might determine the differentiation of Treg / Th17 cells
The propensity of Tregs to convert to Th17 cells in the context of pro-inflammatory stimuli
FOXP3+CD4+ T cells can express RORγt and has the capacity to produce IL-17

34. Balance between Th17 and Treg

35. Balance between Th17 and Treg in RA

36. Therapeutic potential of Tregs
In vivo expansion of CD4+CD25+ Tregs
Anti-CD3 monoclonal Ab (type I DM)
CD28 superagonist
Ex vivo generation of CD4+CD25+ Tregs
Adoptive cell Therapy

37. Clinical applications of Tregs Adoptive cell Therapy

38. Cellular therapy in RA
Tregs may convert to pathogenic cells in human RA
Strategies for expansion and isolation of highly pure FOXP3+ Tregs to be used in cellular therapy

39. Summary A role for Th17 in RA
Inflammation
Cartilage destruction
Bone erosion
Tregs have a key role in immune homeostasis
Important functions in suppressing unwanted inflammatory responses toward self-antigens
Great potential to use these cells in a therapeutic regimen for the treatment of autoimmune diseases