IL-17A Produced by Innate Lymphoid Cells Is Essential for Intestinal Ischemia-Reperfusion Injury.

Ischemia-reperfusion (IR) injury to the small intestine following clamping of the superior mesenteric artery results in an intense local inflammatory response that is characterized by villous damage and neutrophil infiltration. IL-17A, a cytokine produced by a variety of cells in response to inflammatory cytokines released following tissue injury, has been implicated in IR injury. Using Il17a-/- , Il23r-/- , and Rorc-/- mice and administration of anti-IL-17A and anti-IL-23 neutralizing Abs to wild-type mice, we demonstrate that intestinal IR injury depends on IL-17A and that IL-17A is downstream of the binding of autoantibody to ischemia-conditioned tissues and subsequent complement activation. Using bone marrow chimeras, we demonstrate that the IL-17A required for intestinal IR injury is derived from hematopoietic cells. Finally, by transferring autoantibody-rich sera into Rag2γc-/- and Rag2-/- mice, we demonstrate that innate lymphoid cells are the main producers of IL-17A in intestinal IR injury. We propose that local production of IL-17A by innate lymphoid cells is crucial for the development of intestinal IR injury and may provide a therapeutic target for clinical exploitation.

Nod/Ripk2 signaling in dendritic cells activates IL-17A-secreting innate lymphoid cells and drives colitis in T-bet-/-.Rag2-/- (TRUC) mice.

T-bet(-/-).Rag2(-/-) (TRUC) mice spontaneously develop microbiota-driven, TNF-mediated large bowel inflammation that resembles human ulcerative colitis. We show here that IL-23 and IL-1-dependent secretion of IL-17A by innate lymphoid cells (ILCs; defined as CD45(+)lin(-)Thy1(hi)NKp46(-)) is a second critical pathway in this model. Using an in vitro coculture system of bone marrow-derived dendritic cells (DCs) and freshly isolated FACS-purified ILCs, we demonstrate that IL-23 and IL-1 secreted by DCs in response to microbial stimulation work together to induce IL-17A production by ILCs. TNF is not required for IL-17A secretion by ILCs in vitro but synergizes with IL-17A to induce the expression of neutrophil-attracting chemokines. Upstream, activation of the IL-23/IL-17A axis is regulated by nucleotide-binding oligomerization domain containing (Nod)/receptor-interacting serine-threonine kinase 2 (Ripk2) signals in DCs. Genetic ablation of the Nod/Ripk2 signaling pathway protects TRUC mice from developing colitis without affecting the colitogenicity of the intestinal microbiota. Our data provide insight into the complex network of interactions between IL-17A-secreting ILCs and other components of the innate immune system in the development of colitis.

IL-33 promotes innate IFN-γ production and modulates dendritic cell response in LCMV-induced hepatitis in mice.

Recent studies have revealed IL-33 as a key factor in promoting antiviral T-cell responses. However, it is less clear as to how IL-33 regulates innate immunity. In this study, we infected wild-type (WT) and IL-33(-/-) mice with lymphocytic choriomeningitis virus and demonstrated an essential role of infection-induced IL-33 expression for robust innate IFN-γ production in the liver. We first show that IL-33 deficiency resulted in a marked reduction in the number of IFN-γ(+) γδ T and NK cells, but an increase in that of IL-17(+) γδ T cells at 16 h postinfection. Recombinant IL-33 (rIL-33) treatment could reverse such deficiency via increasing IFN-γ-producing γδ T and NK cells, and inhibiting IL-17(+) γδ T cells. We also found that rIL-33-induced type 2 innate lymphoid cells were not involved in T-cell responses and liver injury, since the adoptive transfer of type 2 innate lymphoid cells neither affected the IFN-γ and TNF-α production in T cells, nor liver transferase levels in lymphocytic choriomeningitis virus infected mice. Interestingly, we found that while IL-33 was not required for costimulatory molecule expression, it was critical for DC proliferation and cytokine production. Together, this study highlights an essential role of IL-33 in regulating innate IFN-γ-production and DC function during viral hepatitis.

IL-17A gene transfer induces bone loss and epidermal hyperplasia associated with psoriatic arthritis.

BACKGROUND: Psoriatic arthritis (PsA) is a chronic inflammatory disease characterised by clinical features that include bone loss and epidermal hyperplasia. Aberrant cytokine expression has been linked to joint and skin pathology; however, it is unclear which cytokines are critical for disease initiation. Interleukin 17A (IL-17A) participates in many pathological immune responses; however, its role in PsA has not been fully elucidated. OBJECTIVE: To determine the role of IL-17A in epidermal hyperplasia and bone destruction associated with psoriatic arthritis. DESIGN: An in vivo gene transfer approach was used to investigate the role of IL-17A in animal models of inflammatory (collagen-induced arthritis) and non-inflammatory (receptor activator of NF-κB ligand (RANKL)-gene transfer) bone loss. RESULTS: IL-17A gene transfer induced the expansion of IL-17RA(+)CD11b(+)Gr1(low) osteoclast precursors and a concomitant elevation of biomarkers indicative of bone resorption. This occurred at a time preceding noticeable joint inflammation, suggesting that IL-17A is critical for the induction of pathological bone resorption through direct activation of osteoclast precursors. Moreover, IL-17A induced a second myeloid population CD11b(+)Gr1(high) neutrophil-like cells, which was associated with cutaneous pathology including epidermal hyperplasia, parakeratosis and Munro's microabscesses formation. CONCLUSIONS: Collectively, these data support that IL-17A can play a key role in the pathogenesis of inflammation-associated arthritis and/or skin disease, as observed in PsA.

Glucocorticoid-induced TNF receptor family-related protein ligand regulates the migration of monocytes to the inflamed intestine.

Glucocorticoid-induced TNF receptor family-related protein (GITR) regulates the function of both T cells and antigen-presenting cells (APCs), while the function of GITR ligand (GITR-L) is largely unknown. Here we evaluate the role of GITR-L, whose expression is restricted to APCs, in the development of enterocolitis. On injecting naive CD4(+) T cells, GITR-L(-/-)Rag(-/-) mice develop a markedly milder colitis than Rag(-/-) mice, which correlates with a 50% reduction of Ly6C(+)CD11b(+)MHCII(+) macrophages in the lamina propria and mesenteric lymph nodes. The same result was observed in αCD40-induced acute colitis and during peritonitis, suggesting an altered monocyte migration. In line with these observations, the number of nondifferentiated monocytes was approximately 3-fold higher in the spleen of GITR-L(-/-)Rag(-/-) mice than in Rag(-/-) mice after αCD40 induction. Consistent with the dynamic change in the formation of an active angiotensin II type 1 receptor (AT1) dimer in GITR-L(-/-) splenic monocytes during intestinal inflammation, the migratory capability of splenic monocytes from GITR-L-deficient mice was impaired in an in vitro transwell migration assay. Conversely, αGITR-L reduces the number of splenic Ly6C(hi) monocytes, concomitantly with an increase in AT1 dimers. We conclude that GITR-L regulates the number of proinflammatory macrophages in sites of inflammation by controlling the egress of monocytes from the splenic reservoir.

Glucocorticoid-induced tumor necrosis factor receptor family-related protein regulates CD4(+)T cell-mediated colitis in mice.

BACKGROUND & AIMS: The glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR; also called TNFRSF18 or CD357) regulates the T cell-mediated immune response and is present on surfaces of regulatory T (Treg) cells and activated CD4(+) T cells. We investigated the roles of GITR in the development of colitis in mice. METHODS: Chronic enterocolitis was induced by the transfer of wild-type or GITR(-/-) CD4(+) T cells to GITR(-/-) × Rag(-/-) or Rag(-/-) mice. We determined the severity of colitis by using the disease activity index; measured levels of inflammatory cytokines, T cells, and dendritic cells; and performed histologic analysis of colon samples. RESULTS: Transfer of nonfractionated CD4(+) cells from wild-type or GITR(-/-) donors induced colitis in GITR(-/-) × Rag(-/-) but not in Rag(-/-) mice. Among mice with transfer-induced colitis, the percentage of Treg and T-helper (Th) 17 cells was reduced but that of Th1 cells increased. Treg cells failed to prevent colitis in GITR(-/-) × Rag(-/-) recipients; this was not the result of aberrant function of GITR(-/-) Treg or T effector cells but resulted from an imbalance between the numbers of tolerogenic CD103(+) and PDCA1(+) plasmacytoid dendritic cells in GITR(-/-) mice. This imbalance impaired Treg cell development and expanded the Th1 population in GITR(-/-) × Rag(-/-) mice following transfer of nonfractionated CD4(+) cells. CONCLUSIONS: GITR is not required on the surface of Treg and T effector cells to induce colitis in mice; interactions between GITR and its ligand are not required for induction of colitis. GITR instead appears to control dendritic cell and monocyte development; in its absence, mice develop aggravated chronic enterocolitis via an imbalance of colitogenic Th1 cells and Treg cells.

Signaling lymphocyte activation molecule regulates development of colitis in mice.

BACKGROUND & AIMS: Signaling lymphocyte activation molecule (Slamf)1 is a co-stimulatory receptor on T cells and regulates cytokine production by macrophages and dendritic cells. Slamf1 regulates microbicidal mechanisms in macrophages, therefore we investigated whether the receptor affects development of colitis in mice. METHODS: We transferred CD45RB(hi) CD4(+) T cells into Rag(-/-) or Slamf1(-/-)Rag(-/-) mice to induce colitis. We also induced colitis by injecting mice with an antibody that activates CD40. We determined the severity of enterocolitis based on disease activity index, histology scores, and levels of cytokine production, and assessed the effects of antibodies against Slamf1 on colitis induction. We quantified migration of monocytes and macrophage to inflamed tissues upon induction of colitis or thioglycollate-induced peritonitis and in response to tumor necrosis factor-α in an air-pouch model of leukocyte migration. RESULTS: Colitis was reduced in Slamf1(-/-)Rag(-/-) mice, compared with Rag(-/-) mice, after transfer of CD45RB(hi) CD4(+) T cells or administration of the CD40 agonist. The numbers of monocytes and macrophages were reduced in inflamed tissues of Slamf1(-/-)Rag(-/-) mice, compared with Rag(-/-) mice, after induction of colitis and other inflammatory disorders. An antibody that inhibited Slamf1 reduced the level of enterocolitis in Rag(-/-) mice. CONCLUSIONS: Slamf1 contributes to the development of colitis in mice. It appears to indirectly regulate the appearance of monocytes and macrophages in inflamed intestinal tissues. Antibodies that inhibit Slamf1 reduce colitis in mice, so human SLAMF1 might be a therapeutic target for inflammatory bowel disease.

Investigating combination benefit of PD1 and LAG3 co-blockade using an engineered cellular bioassay.

LAG3 and PD1 are both immunomodulatory receptor that act by inhibiting activation of T cells, producing a more immunosuppressive environment. Even with the recent clinical success of PD1 and LAG3 co-blockade, signal transduction downstream of LAG3 remains largely unknown. We have leveraged an engineered Jurkat (T cell) and Raji (APC) co-culture system to assess simultaneous blockade of PD1 and LAG3 pathways using antibodies. RNA-Seq analysis of cell pellets individually treated with LAG3 or PD1 antibodies revealed modest immune activation however, 5-fold more genes were upregulated upon combination treatment. There were increases in costimulatory genes like CD28, CD5, CD6 as well as intracellular signaling molecules like LCP2 and ITK. Given the role of ERK in immune activation of T cells, pERK levels of Jurkat cells in the assay were evaluated. A very modest activation of pERK was observed with anti-LAG3 compared to anti-PD1 but a combination treatment resulted in prolonged ERK phosphorylation. Treatment of Jurkat cells with a commercial phosphatase inhibitor NSC87877 which can impact many phosphatases resulted in immune activation, measured by increased IL2 levels, only in the presence of LAG3. When NSC87877 was combined with the PD1 antibody, it could phenocopy combination benefit of PD1 and LAG3 blocking antibodies. CD28 has a recognized role in PD1 signaling but the impact on LAG3 signaling remains unknown. CD28 knockout in Jurkat cells affected overall IL-2 response of both LAG3 and PD1 antibody treatment but still retained combination benefit. Taken together this reductionist system highlights differences in downstream effects of LAG3 and PD1 blockade and we believe that the assay may have further utility to dissect convergence of both signaling pathways and augment studies in primary cells.

IL-23 stimulates epidermal hyperplasia via TNF and IL-20R2-dependent mechanisms with implications for psoriasis pathogenesis.

Aberrant cytokine expression has been proposed as an underlying cause of psoriasis, although it is unclear which cytokines play critical roles. Interleukin (IL)-23 is expressed in human psoriasis and may be a master regulator cytokine. Direct intradermal administration of IL-23 in mouse skin, but not IL-12, initiates a tumor necrosis factor-dependent, but IL-17A-independent, cascade of events resulting in erythema, mixed dermal infiltrate, and epidermal hyperplasia associated with parakeratosis. IL-23 induced IL-19 and IL-24 expression in mouse skin, and both genes were also elevated in human psoriasis. IL-23-dependent epidermal hyperplasia was observed in IL-19-/- and IL-24-/- mice, but was inhibited in IL-20R2-/- mice. These data implicate IL-23 in the pathogenesis of psoriasis and support IL-20R2 as a novel therapeutic target.

Endogenous IL-33 enhances Th2 cytokine production and T-cell responses during allergic airway inflammation.

IL-33 is an IL-1-related cytokine which has been implicated in T(h)2-associated biology and allergic diseases in humans and mice. IL-33 stimulates T(h)2 cells, mast cells, eosinophils, basophils, iNKT cells and circulating CD34(+) stem cells to proliferate and produce pro-allergic cytokines such as IL-5 and IL-13. IL-33 mediates its cytokine effects through a receptor consisting of ST2 and IL-1RAcP. Whereas IL-1RAcP is ubiquitously expressed, ST2 expression is cell-type restricted and determines responsiveness to IL-33. Studies employing ST2-deficient mice have reported variable results on the role of this receptor, and consequently IL-33, with regards to allergic lung inflammation. In this study, we demonstrate that IL-33 is important for allergic lung inflammation. Intra-nasal administration of IL-33 triggered an immediate allergic response in the airways, and more importantly, we show that endogenous IL-33 contributes to airway inflammation and peripheral antigen-specific responses in ovalbumin-induced acute allergic lung inflammation using IL-33-deficient mice. Our results suggest that IL-33 is sufficient and required for severe allergic inflammation in the lung and support the concept of IL-33 as a therapeutic target in allergic lung inflammation.

Human Th17 cells comprise heterogeneous subsets including IFN-gamma-producing cells with distinct properties from the Th1 lineage.

Th17 cells have been named after their signature cytokine IL-17 and accumulating evidence indicates their involvement in the induction and progression of inflammatory diseases. In addition to IL-17 single-producing T cells, IL-17/IFN-gamma double-positive T cells are found in significantly elevated numbers in inflamed tissues or blood from patients with chronic inflammatory disorders. Because IFN-gamma is the classical Th1-associated cytokine, the origin and roles of these subsets remain elusive. In this paper, we show that not only IL-17(+)/IFN-gamma(+) but also IFN-gamma(+) (IL-17(-)) cells arise under Th17-inducing condition and have distinct properties from the Th1 lineage. In fact, these populations displayed characteristics reminiscent to IL-17 single-producing cells, including production of IL-22, CCL20, and induction of antimicrobial gene expression from epithelial cells. Live sorted IL-17(+) and Th17-IFN-gamma(+) cells retained expression of IL-17 or IFN-gamma after culture, respectively, whereas the IL-17(+)/IFN-gamma(+) population was less stable and could also become IL-17 or IFN-gamma single-producing cells. Interestingly, these Th17 subsets became "Th1-like" cells in the presence of IL-12. These results provide novel insights into the relationship and functionality of the Th17 and Th1 subsets and have direct implications for the analysis and relevance of IL-17 and/or IFN-gamma-producing T cells present in patients' peripheral blood and inflamed tissues.

From interleukin-23 to T-helper 17 cells: human T-helper cell differentiation revisited.

Protracted inflammation leading to dysregulation of effector T-cell responses represents a common feature of a wide range of autoimmune diseases. The interleukin-12 (IL-12)/T-helper 1 (Th1) pathway was thought to be responsible for the pathogenesis of multiple chronic inflammatory diseases, including psoriasis, inflammatory bowel disease, arthritis, or multiple sclerosis, mainly through their production of interferon-gamma and its effects on macrophage activation and chemokine production. However, this initial concept of T-cell-mediated chronic inflammation required an adjustment with the discovery of an IL-12-related cytokine, designated IL-23. IL-23 was rapidly recognized for its involvement in the establishment of chronic inflammation and in the development of a Th cell subset producing IL-17, designated Th17, which is distinct from the previously reported Th1 and Th2 populations. This review aims to describe the characterization of IL-23 and its receptor, its biological activities, as well as its involvement in the development of human Th17 cells and autoimmunity.

GITR engagement preferentially enhances proliferation of functionally competent CD4+CD25+FoxP3+ regulatory T cells.

Naturally occurring regulatory T cells (Treg) express high levels of glucocorticoid-induced tumour necrosis factor receptor (GITR). However, studies of the role of GITR in Treg biology has been complicated by the observation that upon activation effector CD4(+) T (Teff) cells also express the receptor. Here, we dissect the contribution of GITR-induced signaling networks in the expansion and function of FoxP3(+) Treg. We demonstrate that a high-affinity soluble Fc-GITR-L dimer, in conjugation with alphaCD3, specifically enhances in vitro proliferation of Treg, which retain their phenotypic markers (CD25 and FoxP3) and their suppressor function, while minimally affecting Teff cells. Furthermore, Fc-GITR-L does not impair Teff susceptibility to suppression, as judged by cocultures employing GITR-deficient and GITR-sufficient CD4(+) T-cell subsets. Notably, this expansion of Treg could also be seen in vivo, by injecting FoxP3-IRES-GFP mice with Fc-GITR-L even in the absence of antigenic stimulation. In order to test the efficacy of these findings therapeutically, we made use of a C3H/HeJ hemophilia B-prone mouse model. The use of liver-targeted human coagulation factor IX (hF.IX) gene therapy in this model has been shown to induce liver toxicity and the subsequent failure of hF.IX expression. Interestingly, injection of Fc-GITR-L into the hemophilia-prone mice that were undergoing liver-targeted hF.IX gene therapy increased the expression of F.IX and reduced the anticoagulation factors. We conclude that GITR engagement enhances Treg proliferation both in vitro and in vivo and that Fc-GITR-L may be a useful tool for in vivo tolerance induction.

IL-27 blocks RORc expression to inhibit lineage commitment of Th17 cells.

IL-27 is secreted by APCs in response to inflammatory stimuli and exerts a proinflammatory Th1-enhancing activity but also has significant anti-inflammatory functions. We examined the molecular mechanism by which IL-27 regulates TGFbeta plus IL-6- or IL-23-dependent Th17 development in the mouse and human systems. IL-27 inhibited the production of IL-17A and IL-17F in naive T cells by suppressing, in a STAT1-dependent manner, the expression of the Th17-specific transcription factor RORgamma t. The in vivo significance of the role of IL-27 was addressed in delayed-type hypersensitivity response and experimental autoimmune encephalomyelitis (EAE). By generating mice deficient for the p28 subunit of IL-27, we showed that IL-27 regulated the severity of delayed-type hypersensitivity response and EAE through its effects on Th17 cells. Furthermore, up-regulation of IL-10 in the CNS, which usually occurs late after EAE onset and plays a role in the resolution of the disease, was notably absent in IL-27p28(-/-) mice. These results show that IL-27 acts as a negative regulator of the developing IL-17A response in vivo, suggesting a potential therapeutic role for IL-27 in autoimmune diseases.

Differential expression of monocyte/macrophage- selective markers in human idiopathic pulmonary fibrosis.

Idiopathic interstitial pneumonias are a group of idiopathic interstitial lung diseases of which idiopathic pulmonary fibrosis (IPF) is the lesion of usual interstitial pneumonia. Although the pathogenic mechanisms remain incompletely understood, disease-specific changes in blood, a readily accessible biospecimen, have not been fully characterized. To identify biomarkers from blood and sera, the immune status of IPF patients and control subjects without structural lung disease was quantified by measuring cell surface markers, mRNA levels, and serum proteins. Statistically significant differences in cellular and molecular markers were observed between the 2 groups. The cytokine receptor IL-17RB was significantly higher in CD14+ peripheral blood mononuclear cells (PBMCs) from IPF patients, whereas expression of the chemokine receptor CXCR4 was lower. Gene expression analyses identified 18 differentially expressed genes out of 195 selected. Of these, EMR1, CCR3, UPAR, FCGR2A, OPN, CEACAM3, CD16a, CD18, CD11b, LTF, and LCN2 were up-regulated, whereas IL-17RB, IL-10, PDGFA, CD301/Clec10a, CD25/IL-2RA, IL-23p19, and IL-15 were down-regulated in IPF. Differentially regulated genes were in the functional areas of inflammation and cell signaling. Serum levels of UPAR and OPN were higher in IPF. These observations reveal significant differences in cell and molecular markers involved in monocyte/macrophage activation and migration, and suggest a role for IL-17RB in IPF.

Limited Impact of the Inhibitory Receptor TIGIT on NK and T Cell Responses during Toxoplasma gondii Infection.

Resistance to the parasite Toxoplasma gondii is mediated by NK and T cell production of IFN-γ, but the failure to contract this response can lead to severe T cell-dependent immunopathology. Although the cytokines IL-10 and IL-27 prevent immune hyperactivity during toxoplasmosis, inhibitory receptors, expressed by NK and T cells, are also implicated in this process. The inhibitory receptor TIGIT is expressed on NK and T cells and competes with the costimulatory receptor CD226 for binding of the ligand CD155. During toxoplasmosis, the activation of NK and T cells is associated with increased expression of CD226 and TIGIT, whereas DCs express increased levels of CD155. To determine if the loss of TIGIT impacts NK and T cell activities, wild-type and TIGIT knockout mice were infected with T. gondii During the acute stage of infection, wild-type and TIGIT knockout mice had comparable parasite burdens and similar NK and T cell responses. Likewise, during the chronic phase of this infection, the loss of TIGIT did not affect the magnitude or phenotype of the T cell response nor the ability to control pathogen load. These data suggest that during toxoplasmosis, despite upregulation of relevant ligands, TIGIT signaling does not limit NK and T cell activities. Thus, TIGIT-independent mechanisms dominate the restraint of the immune response during toxoplasmosis.

Conditional Deletion of Pdcd1 Identifies the Cell-Intrinsic Action of PD-1 on Functional CD8 T Cell Subsets for Antitumor Efficacy.

Programmed cell death-1 (PD-1) blockade has a profound effect on the ability of the immune system to eliminate tumors, but many questions remain about the cell types involved and the underlying mechanisms of immune activation. To shed some light on this, the cellular and molecular events following inhibition of PD-1 signaling was investigated in the MC-38 colon carcinoma model using constitutive (PD-1 KO) and conditional (PD1cKO) mice and in wild-type mice treated with PD-1 antibody. The impact on both tumor growth and the development of tumor immunity was assessed. In the PD-1cKO mice, a complete deletion of Pdcd1 in tumor-infiltrating T cells (TILs) after tamoxifen treatment led to the inhibition of tumor growth of both small and large tumors. Extensive immune phenotypic analysis of the TILs by flow and mass cytometry identified 20-different T cell subsets of which specifically 5-CD8 positive ones expanded in all three models after PD-1 blockade. All five subsets expressed granzyme B and interferon gamma (IFNγ). Gene expression analysis of the tumor further supported the phenotypic analysis in both PD-1cKO- and PD-1 Ab-treated mice and showed an upregulation of pathways related to CD4 and CD8 T-cell activation, enhanced signaling through costimulatory molecules and IFNγ, and non-T-cell processes. Altogether, using PD-1cKO mice, we define the intrinsic nature of PD-1 suppression of CD8 T-cell responses in tumor immunity.

An orthogonal IL-2 and IL-2Rß system drives persistence and activation of CAR T cells and clearance of bulky lymphoma.

Chimeric antigen receptor (CAR) T cells induce durable responses in patients with refractory hematological tumors. However, low CAR T cell activity, poor engraftment, or short in-patient persistence can lead to tumor progression or relapse. Furthermore, excessive CAR T cell expansion and activation can result in life-threatening cytokine release syndrome (CRS). Thus, in-patient control of the CAR T cell population is essential. Interleukin-2 (IL-2) is a critical cytokine for T cell proliferation and effector function, but its clinical use is limited by immune-mediated toxicity. Here, we report on an orthogonal IL-2 receptor and ligand system that enables specific in vivo control of CAR T cell expansion and activation, wherein an orthogonal human IL-2 (STK-009) selectively pairs with an orthogonal human IL-2Rß (hoRb) expressed on CAR T cells. STK-009 expands hoRb-expressing CAR T cells in the presence and absence of tumor antigen and maintains the presence of stem cell memory T cells (TSCM) and effector T cells. In preclinical models of human CAR-refractory lymphoma, STK-009 treatment resulted in systemic and intratumoral expansion and activation of hoRb-expressing anti­CD19-CD28ζ CAR T cells (SYNCAR). The orthogonal IL-2 receptor/ligand system delivers complete responses in large subcutaneous lymphomas, even with substantially reduced CAR T cell doses, by selectively expanding and activating CAR T cells in vivo. STK-009 withdrawal allowed normal CAR T cell contraction, thereby limiting CRS induced by tumor antigen­specific T cell activation. These data suggest that the orthogonal IL-2 receptor/ligand system provides the in vivo control necessary to maximize efficacy of CAR T therapies.

Human dendritic cells activated by TSLP and CD40L induce proallergic cytotoxic T cells.

Human thymic stromal lymphopoietin (TSLP) is a novel epithelial cell-derived cytokine, which induces dendritic cell (DC)-mediated CD4+ T cell responses with a proallergic phenotype. Although the participation of CD8+ T cells in allergic inflammation is well documented, their functional properties as well as the pathways leading to their generation remain poorly understood. Here, we show that TSLP-activated CD11c+ DCs potently activate and expand naive CD8+ T cells, and induce their differentiation into interleukin (IL)-5 and IL-13-producing effectors exhibiting poor cytolytic activity. Additional CD40L triggering of TSLP-activated DCs induced CD8+ T cells with potent cytolytic activity, producing large amounts of interferon (IFN)-gamma, while retaining their capacity to produce IL-5 and IL-13. These data further support the role of TSLP as initial trigger of allergic T cell responses and suggest that CD40L-expressing cells may act in combination with TSLP to amplify and sustain pro-allergic responses and cause tissue damage by promoting the generation of IFN-gamma-producing cytotoxic effectors.