CTLA-4 Ablation and Interleukin-12–Driven Differentiation Synergistically Augment Cardiac Pathogenicity of Cytotoxic T Lymphocytes

Abstract

Abstract-CD8ϩ cytotoxic T lymphocytes contribute to viral and autoimmune myocarditis and cardiac allograft rejection. The role of cytotoxic T-lymphocyte-associated antigen (CTLA)-4 as a negative regulator of CD4 ϩ T cells is well defined, yet CTLA-4 regulation of CD8 ϩ T cells is less clear. We studied CTLA-4 regulation of cytotoxic T lymphocytes in a transgenic model of CD8 ϩ T-cell-mediated myocarditis. We generated CTLA-4 Ϫ/Ϫ Rag 2 Ϫ/Ϫ OT-1 mice, the CD8 ϩ T cells of which express an ovalbumin (OVA) peptide-specific, class I major histocompatibility complex-restricted T-cell receptor. CTLA-4Ϫ/ϪTc12 OT-1 effectors, differentiated with interleukin-12 present, are hyperproliferative in vitro, compared with CTLA-4 ϩ/ϩTc12 OT-1 controls. Transfer of low doses of CTLA-4 Ϫ/ϪTc12 OT-1 cells to cMy-mOVA mice, which express OVA on cardiac myocytes, causes severe myocarditis, with 99% mortality, compared with no mortality after transfer of low doses of CTLA-4 ϩ/ϩTc12 OT-1 cells. High doses of CTLA-4 ϩ/ϩTc12 cells cause lethal myocarditis in cMy-mOVA mice, but high doses of CTLA-4 ϩ/ϩTc0 CTL, generated without interleukin-12, are hypoproliferative within the cardiac-draining lymph node and do not significantly infiltrate the heart. In contrast, CTLA-4 Ϫ/ϪTc0 cytotoxic T lymphocytes do proliferate in the cardiac-draining lymph node and diffusely infiltrate the heart. Nonetheless, high doses of CTLA-4 Ϫ/ϪTc0 cells cause only limited tissue damage, and the disease is not lethal. These data show that CTLA-4 regulates myocarditic CD8 ϩ T cell responses and that CTLA-4 deficiency partly overcomes a differentiation block that exists when naïve CD8 ϩ T cells are stimulated without interleukin-12. Therefore, targeting CTLA-4 solely or in conjunction with interleukin-12 could influence effector CD8 ϩ T cell responses in therapeutically beneficial ways. ϩ T-cell activation and differentiation by members of the B7 and CD28 regulatory molecules remain incompletely understood. Cytotoxic T-lymphocyte antigen (CTLA)-4 is a CD28 family member that is expressed on the surface of lymphocytes after T-cell receptor (TCR) stimulation. 1 CTLA-4 and CD28 share specificity for the B7 molecules CD80 (B7-1) and CD86 (B7-2). It is well documented that CD80 and CD86 binding to CTLA-4 on CD4 ϩ T cells results in downregulation of cell-cycle progression and interleukin (IL)-2 production. 2,3 In contrast, there are conflicting studies regarding the effects of CTLA-4 ligation on CD8 ϩ T-cell regulation. 4,5 Several reports indicated that CTLA-4 blockade does not alter cytotoxic T lymphocyte (CTL) responses to lymphocytic choriomeningitis virus, mouse mammary tumor virus, or Leishmania major infection in mice. 4,6,7 Yet experiments with CTLA-4 -deficient class I major histocompatibility complex-restricted TCR transgenic mice indicate that CTLs are hyperresponsive to antigen on restimulation, suggesting a negative regulatory role in CTL activation. 4,5,8 Furthermore, blockade of CTLA-4 with neutralizing antibody augments CTL-mediated responses against tu...

Crosstalk Between Cytotoxic T-Lymphocyte–Associated Antigen-4 and Interleukin-12 in Cytotoxic T-Lymphocyte–Mediated Myocarditis

“…can induced a mild disease characterized by less cell infiltration and less granzyme production (Table). 3 Based on these results, the authors conclude that whereas CTLA-4 limits CTL proliferation and pathogenicity, IL-12 promotes and is necessary for full CTL differentiation in this model. These results suggest that inhibiting CTLA-4 in combination with IL-12 may actually enhance CTL effector function and worsen outcomes.…”

“…3 In this model, when ova peptidespecific CD8 ϩ T lymphocytes are adoptively transferred into the cMy-mOva mice, effector T cells home to the myocardium and induce a robust inflammatory response. ) can induced a mild disease characterized by less cell infiltration and less granzyme production (Table).…”

“…8 The report by Love et al further confirms the important role of IL-12 in CTL antigen-specific differentiation. 3 An alternative explanation for the phenotype observed by Love et al would be the absence of regulatory T cells (Tregs), which express CD4 ϩ CD25 ϩ and function to suppress immunity to infections, tumors, and autoimmune response. In vitro Proliferation ϩ ϩ ϩ…”

“…In this issue, Love et al examine the role of cytotoxic T-lymphocyte-associated antigen (CTLA)-4 in CD8 ϩ T-cell regulation by using a transgenic model of CD8 ϩ T-lymphocyte-mediated myocarditis. 3 One subset of T lymphocytes is the CD8 ϩ T lymphocytes, which are antigen-specific cytotoxic cells that normally protect against infection by killing infected cells via effector molecules such as perforins and granzymes. In the myocardium, CD8 ϩ lymphocytes regulate both myocarditis and allograft rejection by differentiating into cytotoxic T lymphocytes (CTLs).…”

Endothelial-Like Progenitor Cells Engineered to Produce Prostacyclin Rescue Monocrotaline-Induced Pulmonary Arterial Hypertension and Provide Right Ventricle Benefits

“…Cytotoxic T-lymphocyte-associated protein 4 (Ctla4) is an inhibitory receptor expressed on activated T cells. Blocking Ctla4 enhances CD8 + cytotoxic T-lymphocyte-mediated myocarditis 25 and cardiac allograft rejection. 26 Although there is no evidence suggesting that the immune response contributes to the development of RV dysfunction, a recent study showed that rats with autoimmune myocarditis benefit from treatment with a prostacyclin agonist.…”