Th Cell Subsets Dale T. Umetsu, MD, PhD February 27, 2002 n The definition of the Th1/Th2 subsets. n Situations in which Th subsets important. n How do subsets arise and differentiate? n Future directions with this paradigm. –Related T cell subsets –Regulatory T cell subsets.

Expression of cytokines by CD4 T cell subsets IL GM-CSF+++ TNF-  ++ CytokineTh1Th2Th0Thp IFN-  +-+- IL Lymphotoxin+-- IL IL IL-9-+ IL IL-13-+

Generation of Th Cell lines DO11.10 OVA-specific TCR Tg Isolate clonotypic CD4+ T cells OVA + APC rIL-12 Anti-IL-4 mAb OVA + APC rIL-4 Anti-IL-12 mAb OVA + APC rIL-4 rIFN-  Th1 Th2 Th0

Markers of Th1 and Th2 Cells Th1Th2 IFN- , IL-2 IL-12R  2 IL-18R P- and E- selectin receptor CXCR3, CCR5 Tim3 Stat4, T-bet IL-4 IL-1R, IFN-  receptor T1/ST2 (homolog of IL-1R) CCR3, CCR4, CCR8 Tim1? ICOS GATA-3, Stat6

Infection with Leishmania C3H/HeN resistant IFN- , IL-2 BALB/c susceptible IL-4, IL-5, IL-13 Strain result cytokines produced Strain result cytokines produced

Disease States Attributed to an Imbalance in Th1/Th2 Cells Autoimmune diseases Multiple sclerosis Rheumatoid arthritis Diabetes mellitus Crohn’s disease Graft rejection Helminth infection Aborted pregnancy InfectionsLeishmania TB, leprosy Fungal infection HIVAllergy Ulcerative colitis Over production Over production of Th2 cytokines of Th1 cytokines

T Cell Subsets: when are they important? n During chronic antigen stimulation –Chronic infection –Chronic response to auto antigens. –Chronic exposure to allergens. n Not following a single antigenic stimulation, not with fulminant infections.

Th1 Cells Cross Regulate Th2 Cells Th1 cytokines IL-2 IL-2 IFN-  IFN-  IL-12 IL-12 Th2 cytokines IL-4 IL-4 IL-5 IL-5 IL-13 IL-13 IL-12 IFN-  IL-4IL-10

What are the instructive signals for the development of Th1/Th2 cells nCytokine microenvironment nAntigen dose/TCR signaling –Altered peptide ligands nAPC type –Route of antigen administration nCostimulatory signals nHost genetic factors

Signals that influence Th differentiation IL-12, TGF-  IL-4, IL-10, TGF- 

Antigen Effects n High antigen dose induces Th1 cell differentiation; low dose induces Th2 cell differentiation. n Peptides with high affinity for the TCR induces Th1 responses n Altered peptide ligands induce Th2 responses. n Peptide affinity for TCR alters phosphorylation of TCR associated proteins.

Transcription factors that influence Th differentiation T-bet c-mafGATA-3 Innate immunity IL-12

Agarwal, Rao Immunity. 9:765

Lafaille, et al. J. Exp. Med 186:307, Th1(5x10 6 ) Th2 (5x10 6 ) Th1(0.2x10 6 ) Th2(0.2x10 6 )

Attempts to tolerize with MOG results in exacerbation. Genain, et al Science. 274:2054

Transfer of diabetes with both Th1 and Th2 cells Pakala, et al JEM. 186:299.

Th1 cells do not inhibit Th2 cell-induced airway hyperreactivity Hansen, et al J.C.I. 1997

The Th1/Th2 Paradigm and Disease Regulation n Both Th1 and Th2 cells cause disease. n The “opposite” of Th1 cells is not a Th2 cell. n The Th1/Th2 paradigm cannot fully explain immune regulation. n Additional regulatory cells must exist to regulate immune responses.

Tr1 Cells n Develop after stimulation with IL-10. Produce IL-10, IL-5, (TGF- . Produce IL-10, IL-5, (TGF- . n Inhibitory for experimental colitis. n Anti-IL-10 mAb reverses inhibitory effect. n Low proliferative capacity. n Mature DCs producing IL-10 induce Tr1 cells.

Th3 Cells n Generated by oral tolerance induction with low dose antigen. Produce TGF- , IL-4 Produce TGF- , IL-4 n Express regulatory/suppressive activity. TGF-  production may be enhanced by cross-linking of CTLA-4. TGF-  production may be enhanced by cross-linking of CTLA-4.

CD45RB low Cells, CD25 + Cells n CD25 +. n When transferred, have strong regulatory/suppressive activity for colitis and diabetes. Appear to require TGF-  and IL-10 to function. Appear to require TGF-  and IL-10 to function. n CTLA-4 signaling required. n Antigen specificity?

high antigen uncommitted CD4+ T cell Th1 Th2Th3Tr1 Th? CD8  T cell 2000 CD45RB low

Summary-T cell subsets n A major theme in immunology, and documented feature of the immune system. n Subsets of T cells express restricted cytokine profiles n Cells with restricted cytokine profiles (CD4, CD8, NK, NK T, B) have distinct effector functions and regulate immune responses.

Questions that remain n What regulatory cells “balance” Th1 and Th2 cells? What downregulates polarized responses? n How Th subsets are involved in tolerance? n What additional molecular mechanisms regulate cytokine synthesis? n What are the host/genetic factors that regulate cytokine production?