Adaptive Immunity: T Cell Tolerance Jeffrey A. Ledbetter, Ph.D. Rheumatology Sept 20, 2013 figure_15_01 figure_15_02 figure_15_32 Mechanisms of T cell Tolerance Central Tolerance: Positive and Negative Selection in the Thymus Stimulation of Regulatory T cells: TCR signaling without costimulatory signals from CD28 or CD40 IL-2 and IL-2/anti-IL-2 immune complexes expand Tregs T cell apoptosis deletes T cells: Failure of apoptosis allows survival of autoreactive T cells (Fas/FasL KO). Superantigen deletion induces apoptosis of T cells expressing specific Vβ genes. Inhibition by binding to inhibitory receptor CTLA-4 Cortex: Positive Selection for productively rearranged TCR Vβ first with surrogate Vα and then with rearranged Vα Medulla: Negative Selection for self-reactive T cells interacting with mTECs expressing AIRE. Generation of nTregs. Generation and migration of mature CD4 and CD8 T cells to peripheral lymphoid tissue T cell Tolerance: Positive and Negative Selection in the Thymus Diagram of the murine TCRb locus: Jackson et al., Immun Rev 209: 129 (2006). Positive Selection of Thymocytes in Thymus Cortex Thymocytes that productively rearrange TCRβ are positively selected by signals from low levels of cell surface TCR/CD3 that interact with MHC The purpose of surrogate Vα may be to ensure that rearranged Vβ can dimerize and thus come to the cell surface Positively selected Vβ can then ensure that rearranged Vα will dimerize and express on the cell surface Positively selected thymocytes migrate to the medullary area when they begin to encounter mTECs and undergo negative selection DCs take up self antigen from apoptotic MECs and help drive thymocyte clonal deletion Mathis D. et al., Annu. Rev. Immunol. 2009. 27: 287-312 Autoimmune Regulator (AIRE) Expressed by mTECs Controls Negative Selection of Autoreactive T cells Mutation in AIRE cause APECED (autoimmune polyendocrinopathopy type I syndrome), an autosomal recessive monogenic disease Nagamine et al: Positional cloning of the APECED gene. Nat Genet 1997;17:393 AIRE allows medullary thymic epithelial cells to turn on transcriptional expression of many organ-specific proteins to direct negative selection of autoreactive T cells. Anderson et al: Projection of an Immunological Self Shadow Within the Thymus by the Aire Protein. Science 2002; 298: 1395 AIRE controls insulin levels expressed by thymic epithelial cells with variable number polymorphic repeats associated with risk of type I diabetes Cai et al. Diabetes, 2011 AIRE-mediated expression of α-myosin prevents autoimmune myocarditis Lv et al, J. Clin. Invest., 2011 Foxp3 Mutation result in defective CD4+CD25+ Treg development Their deficiency is the hallmark of Immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome-severe autoimmune phenomena including autoimmune enteropathy, dermatitis, thyroiditis, and type 1 diabetes frequently resulting in death w/in first 2 years of life figure_09_28 Autoimmune Regulator (AIRE) Expressed by mTECs Controls Negative Selection of Autoreactive T cells Mutation in AIRE cause APECED (autoimmune polyendocrinopathopy type I syndrome), an autosomal recessive monogenic disease Nagamine et al: Positional cloning of the APECED gene. Nat Genet 1997;17:393 AIRE allows medullary thymic epithelial cells to turn on transcriptional expression of many organ-specific proteins to direct negative selection of autoreactive T cells. Anderson et al: Projection of an Immunological Self Shadow Within the Thymus by the Aire Protein. Science 2002; 298: 1395 AIRE controls insulin levels expressed by thymic epithelial cells with variable number polymorphic repeats associated with risk of type I diabetes Cai et al. Diabetes, 2011 AIRE-mediated expression of α-myosin prevents autoimmune myocarditis Lv et al, J. Clin. Invest., 2011 figure_09_28 figure_15_09 Foxp3 Mutation result in defective CD4+CD25+ Treg development Their deficiency is the hallmark of Immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome-severe autoimmune phenomena including autoimmune enteropathy, dermatitis, thyroiditis, and type 1 diabetes frequently resulting in death w/in first 2 years of life Expression and signaling of CTLA-4 on Tregs of RA patients significantly reduced vs. normal subjects Flores-Borja PNAS 2008 (105) 19396 CTLA-4 KO/mice lack CTLA-4 expression in Tregs  fatal, early-onset lymphoproliferative disease Wing Science 2008 (322) 271 Treg frequency lower in PBMCs of SLE patients vs. healthy controls Bareto, BMC Immunol 2009 (10) 5  Defects in CTLA-4 protein lead to abnormal Treg function in autoimmunity Induces tumor immunity in mice, even to CD40 negative tumors. CD40 agonists in clinical trials in cancer patients face problems from liver toxicity CD40 stimulation inhibition Potential Clinical Utility of CD40 Regulation Anti-CD154 mAb effective in multiple models of autoimmune disease and transplantation. Can induce tolerance in some models due to induction of regulatory T cells Clinical trial of anti-CD154 therapy in SLE patients was halted due to thrombosis Immunostimulation for Cancer Therapy induces autoimmune rebound IFNα therapy of leukemia causes lupus-like response in patients Anti-CTLA-4 is approved for therapy of melanoma: clinical responses are associated with a high frequency of IBD Induces tumor immunity in mice, even to CD40 negative tumors. CD40 agonists in clinical trials in cancer patients face problems from liver toxicity CD40 stimulation inhibition Potential Clinical Utility of CD40 Regulation Anti-CD154 mAb effective in multiple models of autoimmune disease and transplantation. Can induce tolerance in some models due to induction of regulatory T cells Clinical trial of anti-CD154 therapy in SLE patients was halted due to thrombosis figure_09_29 Immunostimulation for Cancer Therapy induces autoimmune rebound IFNα therapy of leukemia causes lupus-like response in patients Anti-CTLA-4 is approved for therapy of melanoma: clinical responses are associated with a high frequency of IBD figure_15_10 Immunostimulation for Cancer Therapy induces autoimmune rebound IFNα therapy of leukemia causes lupus-like response in patients Anti-CTLA-4 is approved for therapy of melanoma: clinical responses are associated with a high frequency of IBD figure_15_37 Effector and Regulatory T‐cell Subsets in Autoimmunity and Tissue Inflammation Scandinavian Journal of Immunology Jager et al, 2010 figure_09_19 figure_09_12 figure_09_29 APC activation regulates T cell responses CD40 Resting APC MHC class II CD86 MHC class II CD40 Activated APC CD80 TLR signals T cell tolerance IL-12 production Th1 polarization B cell isotype switching and affinity maturation T cell activation figure_09_14 figure_09_15 figure_15_05 Costimulation Blockade for Tolerance Induction Individual costimulation inhibitors suppress T cell activation but are not able to induce durable tolerance. Combined CD40 and CD28 inhibitors induce Tolerance in vivo: stimulation of Tregs Other combinations of costimulation inhibtors that include CD2 inhibition have also shown promise in tolerance induction but effects on Tregs not known Role of CD40 in regulation of multiple cell lineages B cell Dendritic cell Endothelial cell Macrophage Required for germinal center formation: Isotype switching and affinity maturation Induces DC maturation and IL-12 production Production of MMPs and inflammatory cytokines Production of inflammatory cytokines Genetic defects in CD154 cause Immunodeficiency disease Hyper IgM Syndrome Costimulation Blockade for Tolerance Induction Individual costimulation inhibitors suppress T cell activation but are not able to induce durable tolerance. Combined CD40 and CD28 inhibitors induce Tolerance in vivo: stimulation of Tregs Other combinations of costimulation inhibtors that include CD2 inhibition have also shown promise in tolerance induction but effects on Tregs not known Role of CD40 in regulation of multiple cell lineages B cell Dendritic cell Endothelial cell Macrophage Required for germinal center formation: Isotype switching and affinity maturation Induces DC maturation and IL-12 production Production of MMPs and inflammatory cytokines Production of inflammatory cytokines Genetic defects in CD154 cause Immunodeficiency disease Hyper IgM Syndrome CD154 is overexpressed in patients with RA and SLE CD154 is increased on activated T and B cells in RA and SLE (Berner et al, Ann Rheum Dis, 2000; Desai-Mehta et al, J Clin Invest, 1996) CD154 in plasma is increased in SLE and RA, and correlates with disease severity and platelet activation (Vakkalanka et al, Arthritis Rheum, 1999; Kata et al, J. Clin Invest, 1999) Ectopic expression of CD154 on B cells induces a lupus-like disease in mice (Higuchi et al, J. Immunol. 2002) Role of CD40 in regulation of multiple cell lineages B cell Dendritic cell Endothelial cell Macrophage Required for germinal center formation: Isotype switching and affinity maturation Induces DC maturation and IL-12 production Production of MMPs and inflammatory cytokines Production of inflammatory cytokines Genetic defects in CD154 cause Immunodeficiency disease Hyper IgM Syndrome Activated platelets Activated CD4 T cell CD154 (CD40L, gp39) Soluble CD154, a biomarker for thrombotic risk B cell: CD40 signals Induce isotype switching and affinity maturation DCs, monocytes, endothelial cells: CD40 signal induces production of Inflammatory cytokines CD40 Expression and Function of CD40 and CD154 Anti-CD154 prevents platelet deaggregation Effect on platelets depends on FcRII binding Anti-CD154 blocks CD40 binding Anti-CD40 Can Stimulate or Inhibit CD4 T Cell CD28 CD40 APC MHC class II TCR APC and T Cell Reciprocal Activation CD4 Resting cells and the initial response to TCR/MHC-peptide recognition lck CD4 and TCR bind MHC CD154 is overexpressed in patients with RA and SLE CD154 is increased on activated T and B cells in RA and SLE (Berner et al, Ann Rheum Dis, 2000; Desai-Mehta et al, J Clin Invest, 1996) CD154 in plasma is increased in SLE and RA, and correlates with disease severity and platelet activation (Vakkalanka et al, Arthritis Rheum, 1999; Kata et al, J. Clin Invest, 1999) Ectopic expression of CD154 on B cells induces a lupus-like disease in mice (Higuchi et al, J. Immunol. 2002) CD4 T Cell CD28 CD40 APC MHC class II TCR APC and T Cell Reciprocal Activation CD4 Resting cells and the initial response to TCR/MHC-peptide recognition lck CD4 and TCR bind MHC CD40 APC CD80 CD86 TCR MHC class II CD28 CTLA4 APC and T Cell Reciprocal Activation CD4 T Cell CD4 lck CD4 and TCR bind MHC CD154 1 2 3 4 TCR CD28 CTLA4 APC and T Cell Reciprocal Activation CD4 T Cell CD4 lck CD4 and TCR bind MHC CD154 Orencia Anti-CD154 CD86 MHC class II CD40 APC CD80 TLR signals IL-12 production Th1 polarization B cell isotype switching and affinity maturation Platelet-derived CD154 DC M1 M2 CTLA4-Ig Inhibits Activation of Effector T cells But not Tregs Purified CD4 naïve (CD45RA) T cells were stimulated For 5 days with allogeneic APCs differentiated from monocytes Inhibition of CD40 is effective in multiple models of autoimmune disease and transplantation Collagen induced arthritis (Durie et al, Science 1993) NZB/NZW Lupus (Mohan et al, J. Immunol, 1995; Early et al, J. Immunol 1996) EAE/MS (Gerritsse et al Proc. Nat. Acad. Sci. USA, 1996) Ophritis (Griggs et al, J. Exp. Med. 1996) Skin transplant (Larsen et al, Nature, 1996) Acute and Chronic GvH (Durie et al, Clin Invest 1994) Hamster antibody MR1 binds to CD154 and blocks CD40 stimulation: MR1 has been used in multiple murine models without detectable toxicity Clinical Development of CD40 Inhibitors Stalled Antibodies to human CD154 failed in phase I trials due to thrombotic events (Biogen) or to lack of efficacy (Idec) Mol Immunol. 2008 Feb;45(4):937-44. Platelet pro-aggregatory effects of CD40L monoclonal antibody. Mirabet M et al J Am Coll Cardiol. 2009 Aug 18;54(8):669-77. The CD40/CD40 ligand system: linking inflammation with atherothrombosis Antoniades C, et al Trends Immunol. 2009 Apr;30(4):165-72. Epub 2009 Mar 11. CD154 and its receptors in inflammatory vascular pathologies. Hassan GS et al Combined Inhibition of CD28 and CD40 for Durable Tolerance in Autoimmune Disease CTLA4-Ig plus anti-CD154 (CD40L, gp39) therapy generates transplantation tolerance Skin and heart allografts (Larson et al, Nature 381: 434, 1996). Combination therapy prevented lupus in NZB/NZW mice (Daikh et al, J Immunol 159: 3104, 1997) Combination therapy allowed renal transplantation in nonhuman primates without other immunosuppression (Kirk et al, PNAS 94: 8789, 1997) CTLA4-Ig (abatacept) approved for RA, but initial anti-CD154 clinical trials failed Verbinnen, B et al., 2008. Verbinnen, B et al., 2008. Koreth et al, NEJM, 2011 Saadoun et al, NEJM, 2011