Summary T cell engineering is a powerful means to rapidly generate anti-tumor T cells. The costimulatory properties of second-generation chimeric antigen receptors (CARs) determine the overall potency of adoptively transferred T cells. Utilizing an in vivo “stress test” to challenge CD19-targeted T cells, we studied the functionality and persistence imparted by 7 different CAR structures providing CD28 and/or 4-1BB costimulation. One configuration, which utilizes two signaling domains (CD28 and CD3ζ) and the 4-1BB ligand, provided the highest therapeutic efficacy, showing balanced tumoricidal function and increased T cell persistence accompanied by an elevated CD8/CD4 ratio and decreased exhaustion. Remarkably, induction of the IRF7/IFNβ pathway was required for optimal anti-tumor activity. Thus, 1928z-41BBL T cells possess strikingly potent intrinsic and immunomodulatory qualities.

Chimeric antigen receptors (CARs) are synthetic antigen receptors that reprogram T cell specificity, function and persistence1. Patient-derived CAR T cells have demonstrated remarkable efficacy against a range of B-cell malignancies1–3, and the results of early clinical trials suggest activity in multiple myeloma4. Despite high complete response rates, relapses occur in a large fraction of patients; some of these are antigen-negative and others are antigen-low1,2,4–9. Unlike the mechanisms that result in complete and permanent antigen loss6,8,9, those that lead to escape of antigen-low tumours remain unclear. Here, using mouse models of leukaemia, we show that CARs provoke reversible antigen loss through trogocytosis, an active process in which the target antigen is transferred to T cells, thereby decreasing target density on tumour cells and abating T cell activity by promoting fratricide T cell killing and T cell exhaustion. These mechanisms affect both CD28- and 4-1BB-based CARs, albeit differentially, depending on antigen density. These dynamic features can be offset by cooperative killing and combinatorial targeting to augment tumour responses to immunotherapy.

Chimeric antigen receptors (CARs) are synthetic receptors that target and reprogram T cells to acquire augmented antitumor properties1. CD19-specific CARs that comprise CD28 and CD3ζ signaling motifs2 have induced remarkable responses in patients with refractory leukemia3-5 and lymphoma6 and were recently approved by the US Food and Drug Administration7. These CARs program highly performing effector functions that mediate potent tumor elimination4,8 despite the limited persistence they confer on T cells3-6,8. Extending their functional persistence without compromising their potency should improve current CAR therapies. Strong T cell activation drives exhaustion9,10, which may be accentuated by the redundancy of CD28 and CD3ζ signaling11,12 as well as the spatiotemporal constraints imparted by the structure of second-generation CARs2. Thus, we hypothesized that calibrating the activation potential of CD28-based CARs would differentially reprogram T cell function and differentiation. Here, we show that CARs encoding a single immunoreceptor tyrosine-based activation motif direct T cells to different fates by balancing effector and memory programs, thereby yielding CAR designs with enhanced therapeutic profiles.

TNF-like weak inducer of apoptosis (TWEAK), a member of the TNF superfamily, is a prominent inducer of proinflammatory cytokines in vitro and in vivo. We previously found that kidney cells display the TWEAK receptor Fn14, and that TWEAK stimulation of mesangial cells and podocytes induces a potent proinflammatory response. Several of the cytokines up-regulated in the kidney in response to TWEAK are instrumental in Lupus nephritis; we therefore hypothesized that TWEAK/Fn14 interactions may be important in the cascade(s) leading to renal damage in systemic Lupus erythematosus. In this study, we analyzed the effects of Fn14 deficiency in the chronic graft-vs-host model of SLE, and the benefits of treatment with an anti-TWEAK mAb in this mouse model. We found that anti-nuclear Ab titers were no different between C57BL/6 Fn14 wild-type and deficient mice injected with alloreactive bm12 splenocytes. However, kidney disease was significantly less severe in Fn14 knockout mice. Furthermore, kidney IgG deposition, IL-6, MCP-1, RANTES, and IP-10, as well as macrophage infiltration, were significantly decreased in Fn14-deficient mice with induced lupus. Similarly, mice with induced Lupus treated with an anti-TWEAK neutralizing mAb had significantly diminished kidney expression of IL-6, MCP-1, IL-10, as well as proteinuria, but similar autoantibody titers, as compared with control-treated mice. We conclude that TWEAK is an important mediator of kidney damage that acts by promoting local inflammatory events, but without impacting adaptive immunity in this experimental LN model. Thus, TWEAK blockade may be a novel therapeutic approach to reduce renal damage in SLE.

Objective. Cross-reactivity with kidney antigens is believed to be a critical determinant in the renal pathogenicity of anti-double-stranded DNA (anti-dsDNA) antibodies. Murine nephritogenic anti-dsDNA antibodies have been shown to cross-react with ␣-actinin, and anti-␣-actinin antibodies have been found to be deposited in the kidneys of lupus mice with active nephritis. Furthermore, in humans with systemic lupus erythematosus (SLE), it has been found that a greater proportion of polyclonal IgG anti-dsDNA antibodies from patients with renal involvement bind to ␣-actinin than do those from patients without renal disease. We undertook this study to substantiate a direct link between cross-reactive anti-dsDNA/anti-␣-actinin antibodies and the pathogenesis of lupus nephritis in humans.Methods. A panel of 10 anti-dsDNA and/or anti-␣-actinin antibodies was generated by Epstein-Barr virus transformation of lymphocytes from patients with SLE and was extensively characterized. Antibody binding was studied by enzyme-linked immunosorbent assay and Western blotting. Antibody potential for pathogenicity was assessed by measuring binding to isolated glomeruli and mesangial cells and by evaluation of histologic features of the kidney following injection in vivo.Results. All anti-dsDNA antibodies isolated also bound ␣-actinin. Cross-reactive antibodies bound to mesangial cells and to isolated glomeruli ex vivo. Binding to glomeruli was not inhibited by DNase treatment, but could be abrogated by ␣-actinin. Furthermore, histopathologic abnormalities seen in mice injected intraperitoneally with a cross-reactive cell line included fusion of podocyte foot processes and subepithelial and subendothelial deposition.Conclusion. These studies provide strong support for the hypothesis that ␣-actinin is a major crossreactive target for anti-dsDNA antibodies in SLE patients. Cross-reactive anti-dsDNA/anti-␣-actinin antibodies from SLE patients are pathogenic and may contribute to the kidney lesions in lupus nephritis.

NK cells are regulated by inhibiting and activating cell surface receptors. Most inhibitory receptors recognize MHC-class I antigens, and protect healthy cells from NK cell-mediated auto-aggression. However, certain activating receptors, including the human killer cell Ig-like receptor (KIR) 2DS1, also recognize MHC-class I. This raises the question of how NK cells expressing such activating receptors are tolerized to host tissues. We investigated whether the presence of HLA-C2, the cognate ligand for 2DS1, induces tolerance in 2DS1-expressing NK cells. Anti-HLA-C2 activity could be detected in vitro in some 2DS1 positive NK clones irrespective of presence or absence of HLA-C2 ligand in the donor. The frequency of anti-HLA-C2 reactivity was high in donors homozygous for HLA-C1. Surprisingly, there was no significant difference in frequency of anti-HLA-C2 cytotoxicity in donors heterozygous for HLA-C2 and donors without HLA-C2 ligand. However, donors homozygous for HLA-C2 had significantly reduced frequency of anti-HLA-C2 reactive clones as compared to all other donors. 2DS1 positive clones that express inhibitory KIR for self-HLA class I were commonly non-cytotoxic, and anti-HLA-C2 cytotoxicity was nearly exclusively restricted to 2DS1 single positive clones lacking inhibitory KIR. 2DS1 single positive NK clones with anti-HLA-C2 reactivity were also present post-transplantation in HLA-C2 positive recipients of hematopoietic stem cell transplants from 2DS1 positive donors. These results demonstrate that many NK cells with anti-HLA-C2 reactivity are present in HLA-C1 homozygous and heterozygous donors with 2DS1. In contrast, 2DS1 positive clones from HLA-C2 homozygous donors are frequently tolerant to HLA-C2.

Summary The effector potential of NK cells is counterbalanced by their sensitivity to inhibition by “self” MHC class I molecules in a process called “education”. In humans, interactions between inhibitory killer immunoglobulin-like receptors (KIR) and human MHC (HLA) mediate NK cell education. In HLA-B* 27:05+ transgenic mice and patients undergoing HLA-mismatched hematopoietic cell transplantation (HCT), NK cells derived from human CD34+ stem cells were educated by HLA from both donor hematopoietic cells and host stromal cells. Furthermore, mature human KIR3DL1+ NK cells gained reactivity after adoptive transfer to HLA-B*27:05+ mice or bone marrow chimeric mice where HLA-B*27:05 was restricted to either the hematopoietic or stromal compartment. Silencing of HLA in primary NK cells diminished NK cell reactivity, while acquisition of HLA from neighboring cells increased NK cell reactivity. Altogether, these findings reveal roles for cell-extrinsic HLA in driving NK cell reactivity upward, and cell–intrinsic HLA in maintaining NK cell education.

The human liver is enriched in natural killer cells (NK cells) which are potent effectors of the innate immune system. We have determined that liver NK cells freshly isolated from surgical specimens from patients with hepatic malignancy have less cytolytic activity than autologous blood NK cells. This difference was due to a higher proportion of CD16− NK cells in the liver and reduced cytotoxicity by CD16+ liver NK cells compared with their blood counterparts. CD16+ liver NK cells had similar expression of activating NK receptors and had similar intracellular granzyme B and perforin content compared with CD16+ blood NK cells. CD16+ liver NK cells contained a reduced fraction of cells with inhibitory killer immunoglobulin-like receptors specific for self-MHC class I (self-KIR) and an increased fraction of self-KIRnegNKG2Apos and self-KIRnegNKG2Aneg cells. Using single-cell analysis of intracellular interferon-gamma (IFN-γ) production and cytotoxicity assays, we determined that CD16+ liver NK cells expressing self-KIR were more responsive to target cells than those cells that did not express self-KIR molecules. CD16+ liver NK cells gained cytolytic function when stimulated with IL-2 or cultured with LPS or PolyI:C-activated autologous liver Kupffer cells. Thus, the human liver contains NK cell subsets which have reduced effector function, but under appropriate inflammatory conditions become potent killers.