Tania F. Rowley

Cutting Edge: A Critical Role for CD70 in CD8 T Cell Priming by CD40-Licensed APCs

The CD154/CD40 interaction is an important pathway of CD4 T cell help for CD8 T cell responses. In this study, we address the role of CD70, a member of the TNF superfamily and the ligand for the T cell costimulatory receptor CD27, in CD40-mediated priming of CD8 T cells. Using an agonistic anti-CD40 mAb to mimic the CD154/CD40 interaction we demonstrate that the priming of OT-I TCR transgenic or endogenous mouse OVA-specific CD8 T cells is critically dependent on CD70/CD27 interaction. CD70 blockade inhibited CD40-mediated clonal expansion of CD8 T cells and reduced the number of memory CD8 T cells generated. Furthermore, CD70 blockade during the initial priming of CD8 T cells inhibited the ability of memory CD8 T cells to expand in response to a second encounter with Ag. Our data indicate that CD70 expression on APCs plays a key role in CD40-dependent CD8 T cell responses.

Expression and costimulatory effects of the TNF receptor superfamily members CD134 (OX40) and CD137 (4-1BB), and their role in the generation of anti-tumor immune responses

This study addresses the relative importance of CD134 (OX40) and CD137 (4‐1BB) in the costimulation of CD4+ and CD8+ T cells under comparable conditions of antigenic stimulation. We demonstrate that CD134 is capable of directly costimulating CD8+ T cells. However, costimulation of CD8+ T cells by CD134 is less potent than that triggered by CD137. The higher costimulatory activity of CD137, when compared with CD134, correlates well with its faster expression kinetics and higher levels on CD8+ T cells. Furthermore, induction of CD137 expression on CD8+ T cells is highly sensitive to low levels of TCR stimulation, which is in contrast with CD134. Conversely, CD134 is more effective than CD137 in costimulating CD4+ T cells. This, however, could not be attributed to differential expression. We also demonstrate that the transient nature of CD134 and CD137 expression on activated CD4+ T cells is the resultof proteolytic shedding. Consistent with the greater ability of CD137 to costimulate CD8+ T cells, stimulation of CD137 in vivo is considerably more effective than CD134 in augmenting anti‐tumor immune responses. Therefore, agents that stimulate signaling via CD137 are likely to be more useful in clinical conditions where highly effective CD8+ CTL responses are required.

The Death Receptor 3–TNF-like protein 1A pathway drives adverse bone pathology in inflammatory arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease of synovial joints that is associated with cartilage and bone destruction. Death Receptor 3 (DR3), a tumor necrosis factor (TNF) receptor superfamily member, has recently been associated with the pathogenesis of RA. We demonstrate that absence of DR3 confers resistance to the development of adverse bone pathology in experimental antigen-induced arthritis (AIA). DR3ko mice exhibited a reduction in all histopathological hallmarks of AIA but, in particular, failed to develop subchondral bone erosions and were completely protected from this characteristic of AIA. In contrast, TNF-like protein 1A (TL1A), the ligand for DR3, exacerbated disease in a dose- and DR3-dependent fashion. Analysis of osteoclast number within AIA joint revealed a reduction in areas susceptible to bone erosion in DR3ko mice, whereas in vitro osteoclastogenesis assays showed that TL1A could directly promote osteoclastogenesis in mouse and man. Treatment with antagonistic anti-TL1A mAb protected animals in a systemic model of RA disease collagen-induced arthritis. We therefore conclude that the DR3–TL1A pathway regulates joint destruction in two murine models of arthritis and represents a potential novel target for therapeutic intervention in inflammatory joint disease.

Stimulation by Soluble CD70 Promotes Strong Primary and Secondary CD8+ Cytotoxic T Cell Responses In Vivo

Identification of the signals required for optimal differentiation of naive CD8+ T cells into effector and memory cells is critical for the design of effective vaccines. In this study we demonstrate that CD27 stimulation by soluble CD70 considerably enhances the magnitude and quality of the CD8+ T cell response. Stimulation with soluble CD70 in the presence of Ag significantly enhanced the proliferation of CD8+ T cells and their ability to produce IL-2 and IFN-γ in vitro. Administration of Ag and soluble CD70 resulted in a massive (>300-fold) expansion of Ag-specific CD8+ T cells in vivo, which was due to the enhanced proliferation and survival of activated T cells. In mice that received Ag and soluble CD70, CD8+ T cells developed into effectors with direct ex vivo cytotoxicity. Furthermore, unlike peptide immunization, which resulted in a diminished response after rechallenge, CD27 stimulation during the primary challenge evoked a strong secondary response upon rechallenge with the antigenic peptide. Thus, in addition to increasing the frequency of primed Ag-specific T cells, CD27 signaling during the primary response instills a program of differentiation that allows CD8+ T cells to overcome a state of unresponsiveness. Taken together these results demonstrate that soluble CD70 has potent in vivo adjuvant effects for CD8+ T cell responses.

Requirement for CD70 in CD4+ Th Cell-Dependent and Innate Receptor-Mediated CD8+ T Cell Priming

Dendritic cell (DC) conditioning by CD4+ T cells, or via engagement of innate receptors, is thought to be essential for CD8+ T cell priming. However, the molecular features that distinguish a conditioned DC from an unconditioned DC are poorly defined. In this study, we investigate the role of CD70, a member of the TNF superfamily that is expressed on activated DC, in CD4+ Th-dependent and -independent CD8+ T cell responses. We demonstrate that CD70 is required for CD4+ T cell-dependent priming of CD8+ T cells as well as priming mediated by the viral signature, dsRNA. Accordingly, mice that were subjected to CD70 blockade during the primary response fail to generate a memory CD8+ T cell response. Furthermore, we find that CD70 is dispensable for CD4+ T cell expansion and help for B cells, thus suggesting a direct role for CD70 in CD8+ T cell priming. Our results show that the innate and adaptive (CD4+ T cells) arms of the immune system use a common signaling pathway in driving CD8+ T cell responses and suggest that expression of CD70 on DC represents the hallmark of conditioned DC.

Triggering of TNFRSF25 promotes CD8+ T‐cell responses and anti‐tumor immunity

TNFRSF25 is a member of the TNF receptor superfamily (TNFRSF) that binds to the TNF‐like protein TL1A. Although recent studies have demonstrated a role for TNFRSF25 in regulating CD4+ T‐cell responses, it remains to be determined if TNFRSF25 functions as a costimulatory receptor for CD8+ T cells. Here, we demonstrate that ectopic expression of TL1A on mouse plasmacytomas promotes elimination of tumor cells in a CD8+ T‐cell‐dependent manner and renders mice immune to a subsequent challenge with tumor cells. To gain further insight into the role of TNFRSF25 in CD8+ T‐cell responses, we analyzed the effect of TNFRSF25 triggering on OT‐I TCR transgenic T cells. We demonstrate that TNFRSF25 triggering in vivo with soluble TL1A promotes the proliferation and accumulation of antigen‐specific CD8+ T cells as well as their differentiation into CTLs. Furthermore, we show that TNFRSF25 also functions as a costimulatory receptor for memory CD8+ T cells. Thus, TNFRSF25 triggering enhances the secondary expansion of endogenous antigen‐specific memory CD8+ T cells. Our data suggest that TNFRSF25 agonists, such as soluble TL1A, could potentially be used to enhance the immunogenicity of vaccines that aim to elicit human anti‐tumor CD8+ T cells.

CD27 costimulation contributes substantially to the expansion of functional memory CD8(+) T cells after peptide immunization.

Naive T cells require signals from multiple costimulatory receptors to acquire full effector function and differentiate to long‐lived memory cells. The costimulatory receptor, CD27, is essential for optimal T‐cell priming and memory differentiation in a variety of settings, although whether CD27 is similarly required during memory CD8+ T‐cell reactivation remains controversial. We have used OVA and anti‐CD40 to establish a memory CD8+ T‐cell population and report here that their secondary expansion, driven by peptide and anti‐CD40, polyI:C, or LPS, requires CD27. Furthermore, antigenic peptide and a soluble form of the CD27 ligand, CD70 (soluble recombinant CD70 (sCD70)), is sufficient for secondary memory CD8+ T‐cell accumulation at multiple anatomical sites, dependent on CD80/86. Prior to boost, resting effector‐ and central‐memory CD8+ T cells both expressed CD27 with greater expression on central memory cells. Nonetheless, both populations upregulated CD27 after TCR engagement and accumulated in proportion after boosting with Ag and sCD70. Mechanistically, sCD70 increased the frequency of divided and cytolytic memory T cells, conferred resistance to apoptosis and enabled retardation of tumor growth in vivo. These data demonstrate the central role played by CD27/70 during secondary CD8+ T‐cell activation to a peptide Ag, and identify sCD70 as an immunotherapeutic adjuvant for antitumor immunity.

Inhibition of p38 mitogen-activated protein kinase unmasks a CD30-triggered apoptotic pathway in anaplastic large cell lymphoma cells.

CD30, a non–death domain–containing member of the tumor necrosis factor receptor superfamily, triggers apoptosis in anaplastic large cell lymphoma cells. The CD30 signaling pathways that lead to the induction of apoptosis are poorly defined. Here, we show that the induction of apoptosis by CD30 requires concurrent inhibition of p38 mitogen-activated protein kinase, which itself is activated by engagement of CD30 with CD30 ligand. Treatment of anaplastic large cell lymphoma cells with CD30 ligand and pharmacologic inhibitors of p38 mitogen-activated protein kinase, but not with CD30 ligand or inhibitors alone, triggered the activation of caspase-8 and the induction of apoptosis. Caspase-8 activation occurred within a few hours (2.5–4 h) after receptor triggering, was unaffected by the neutralization of ligands for the death domain–containing receptors TNFR1, Fas, DR3, DR4, or DR5, but was abolished by the expression of a dominant-negative form of the adaptor protein FADD. Importantly, we show that expression of the caspase-8 inhibitor c-FLIPS is strongly induced by the CD30 ligand, and that this is dependent on the activation of p38 mitogen-activated protein kinase. Thus, we provide evidence that the induction of apoptosis by CD30 in anaplastic large cell lymphoma cells is normally circumvented by the activation of p38 mitogen-activated protein kinase. These findings have implications for CD30-targeted immunotherapy of anaplastic large cell lymphoma. [Mol Cancer Ther 2007;6(2):703–11]

The role of death receptor 3 in inflammatory arthritis

2008 The Authors Journal Compilation 2008 Blackwell Publishing Ltd, Immunology, 125, Supplement 1, 1 144 Metchnikoff Centenary – Macrophages and Immunity IS2 Heterogeneity of mouse and human monocytesThis paper looks at the effects of dust allergen and LPS concentrations on biomarkers of asthma in adults with house dust mite-sensitive asthma.

The role of death receptor 3 in inflammatory arthritis [Abstract]

2008 The Authors Journal Compilation 2008 Blackwell Publishing Ltd, Immunology, 125, Supplement 1, 1 144 Metchnikoff Centenary – Macrophages and Immunity IS2 Heterogeneity of mouse and human monocytesThis paper looks at the effects of dust allergen and LPS concentrations on biomarkers of asthma in adults with house dust mite-sensitive asthma.