Facts and Hopes in Cancer Antigens Recognized by T Cells.

T cells are key effectors of our immune response against tumors and exert their antitumor effects upon recognizing a variety of tumor-specific peptides presented by HLA molecules on the surface of tumor cells. The identification of the tumor-specific antigens of a given tumor is not required for immune checkpoint therapy (ICT), which mainly reactivates existing tumor-specific T cells together with T cells of unknown specificities. To decrease the activation of non-tumor-specific T cells, active or passive immunizations against tumor-specific antigens are considered. These immunizations require the identification of at least some of the tumor-specific antigens displayed on the tumor cells of a patient. While this has become an easy task for tumors with a large number of mutations generating neoantigens, it remains difficult for the remainder. Here, we review some facts about human tumor-specific or tumor-associated antigens, as well as some hopes for their future use in cancer immunotherapy.

Therapeutic activity of GARP:TGF-ß1 blockade in murine primary myelofibrosis.

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by the clonal expansion of myeloid cells, notably megakaryocytes (MKs), and an aberrant cytokine production leading to bone marrow (BM) fibrosis and insufficiency. Current treatment options are limited. TGF-ß1, a profibrotic and immunosuppressive cytokine, is involved in PMF pathogenesis. While all cell types secrete inactive, latent TGF-ß1, only a few activate the cytokine via cell type-specific mechanisms. The cellular source of the active TGF-ß1 implicated in PMF is not known. Transmembrane protein GARP binds and activates latent TGF-ß1 on the surface of regulatory T lymphocytes (Tregs) and MKs or platelets. Here, we found an increased expression of GARP in the BM and spleen of mice with PMF and tested the therapeutic potential of a monoclonal antibody (mAb) that blocks TGF-ß1 activation by GARP-expressing cells. GARP:TGF-ß1 blockade reduced not only fibrosis but also the clonal expansion of transformed cells. Using mice carrying a genetic deletion of Garp in either Tregs or MKs, we found that the therapeutic effects of GARP:TGF-ß1 blockade in PMF imply targeting GARP on Tregs. These therapeutic effects, accompanied by increased IFN-γ signals in the spleen, were lost upon CD8 T-cell depletion. Our results suggest that the selective blockade of TGF-ß1 activation by GARP-expressing Tregs increases a CD8 T-cell-mediated immune reaction that limits transformed cell expansion, providing a novel approach that could be tested to treat patients with myeloproliferative neoplasms.

Pandemic chilblains: Are they SARS-CoV-2-related or not?

The exact etiopathology of chilblains observed during the Coronavirus Disease 2019 (COVID-19) pandemic is still unclear. Initially, SARS-CoV-2 appeared as the obvious causing agent, but two years of various investigations have failed to convincingly support its direct implication. Most affected individuals have no detectable virus, no anti-SARS-CoV-2 antibodies and no symptoms of COVID-19. Analyses of skin biopsies similarly failed to unambiguously demonstrate presence of the virus or its genome. In a recent hypothesis, SARS-CoV-2 would cause the lesions before being promptly eliminated by unusually strong type I interferon responses. With others, we feel that environmental factors have not been sufficiently considered, in particular cold exposure related to unprecedented containment measures. The cause of pandemic chilblains remains a stimulating puzzle which warrants further investigation.

Blocking GARP-mediated activation of TGF-ß1 did not alter innate or adaptive immune responses to bacterial infection or protein immunization in mice.

Transmembrane protein GARP binds latent TGF-ß1 to form GARP:(latent)TGF-ß1 complexes on the surface of several cell types including Tregs, B-cells, and platelets. Upon stimulation, these cells release active TGF-ß1. Blocking TGF-ß1 activation by Tregs with anti-GARP:TGF-ß1 mAbs overcomes resistance to PD1/PD-L1 blockade and induces immune-mediated regressions of murine tumors, indicating that Treg-derived TGF-ß1 inhibits anti-tumor immunity. TGF-ß1 exerts a vast array of effects on immune responses. For example, it favors differentiation of TH17 cells and B-cell switch to IgA production, two important processes for mucosal immunity. Here, we sought to determine whether treatment with anti-GARP:TGF-ß1 mAbs would perturb immune responses to intestinal bacterial infection. We observed no aggravation of intestinal disease, no systemic dissemination, and no alteration of innate or adaptative immune responses upon oral gavage of C. rodentium in highly susceptible Il22r-/- mice treated with anti-GARP:TGF-ß1 mAbs. To examine the effects of GARP:TGF-ß1 blockade on Ig production, we compared B cell- and TH cell- responses to OVA or CTB protein immunization in mice carrying deletions of Garp in Tregs, B cells, or platelets. No alteration of adaptive immune responses to protein immunization was observed in the absence of GARP on any of these cells. Altogether, we show that antibody-mediated blockade of GARP:TGF-ß1 or genetic deletion of Garp in Tregs, B cells or platelets, do not alter innate or adaptive immune responses to intestinal bacterial infection or protein immunization in mice. Anti-GARP:TGF-ß1 mAbs, currently tested for cancer immunotherapy, may thus restore anti-tumor immunity without severely impairing other immune defenses. PRéCIS: Immunotherapy with GARP:TGF-ß1 mAbs may restore anti-tumor immunity without impairing immune or inflammatory responses required to maintain homeostasis or host defense against infection, notably at mucosal barriers.

High p16INK4a, a marker of cellular senescence, is associated with renal injury, impairment and outcome in lupus nephritis.

OBJECTIVES: Because a significant fraction of patients with lupus nephritis (LN) develops renal impairment, there is a need to better understand the mechanisms underlying disease progression. Here, we assessed for cellular senescence in the LN kidney, and its association with disease severity and outcome. METHODS: We enumerated the number of cells positive for p16INK4a protein, a marker of cellular senescence, by immunohistochemistry followed by digital quantification, on renal biopsies from 40 patients with active LN. We tested for an association of p16INK4a with renal fibrosis, CD8+ T cell infiltration, systemic disease and renal function at baseline and at 5 years. RESULTS: The presence of p16INK4a-positive cells was significantly associated with lower estimated glomerular filtration rate at baseline and 5 years post-treatment, independently of patient demographics and systemic disease parameters. It was also associated with higher baseline renal fibrosis and CD8+ T cell infiltration. Interestingly, we observed marked spatial co-distribution of glomerular p16INK4a-positive cells with CD8+ T cells. CONCLUSION: We demonstrate, for the first time, that LN biopsies characterised by renal impairment display increased p16INK4a-positive cells, associated with higher fibrosis and CD8+ T cell infiltration. Cellular senescence may represent a kidney-intrinsic disease mechanism and potentially, a novel therapeutic target in LN.

Common Transcriptomic Effects of Abatacept and Other DMARDs on Rheumatoid Arthritis Synovial Tissue.

Objectives: Our goal was to assess for the histological and transcriptomic effects of abatacept on RA synovia, and to compare them with previously published data from four other DMARDs: tocilizumab, rituximab, methotrexate, and adalimumab. Methods: Synovial tissue was obtained using ultrasound-guided biopsy from affected joints of 14 patients, before and 16 weeks after treatment with subcutaneous abatacept 125 mg weekly. Paraffin-sections were stained and scored for CD3+, CD20+, and CD68+ cell infiltration. Transcriptional profiling was performed using GeneChip Human Genome U133 Plus 2.0 arrays (Affymetrix) and analyzed on Genespring GX (Agilent). Pathway analyses were performed on Genespring GX, Metascape, and EnrichR. Results: Gene expression analysis identified 304 transcripts modulated by abatacept in synovial tissue. Downregulated genes were significantly enriched for immune processes, strongly overlapping with our findings on other therapies. Data were pooled across these studies, revealing that genes downregulated by DMARDs are significantly enriched for both T-cell and myeloid leukocyte activation pathways. Interestingly, DMARDs seem to have coordinate effects on the two pathways, with a stronger impact in good responders to therapy as compared to moderate and non-responders. Conclusion: We provide evidence that the effects of five DMARDs on the RA synovium culminate in the same pathways. This confirms previous studies suggesting the existence of common mediators downstream of DMARDs, independent of their primary targets.

Combined Blockade of GARP:TGF-ß1 and PD-1 Increases Infiltration of T Cells and Density of Pericyte-Covered GARP+ Blood Vessels in Mouse MC38 Tumors.

When combined with anti-PD-1, monoclonal antibodies (mAbs) against GARP:TGF-ß1 complexes induced more frequent immune-mediated rejections of CT26 and MC38 murine tumors than anti-PD-1 alone. In both types of tumors, the activity of anti-GARP:TGF-ß1 mAbs resulted from blocking active TGF-ß1 production and immunosuppression by GARP-expressing regulatory T cells. In CT26 tumors, combined GARP:TGF-ß1/PD-1 blockade did not augment the infiltration of T cells, but did increase the effector functions of already present anti-tumor T cells. Here we show that, in contrast, in MC38, combined GARP:TGF-ß1/PD-1 blockade increased infiltration of T cells, as a result of increased extravasation of T cells from blood vessels. Unexpectedly, combined GARP:TGF-ß1/PD-1 blockade also increased the density of GARP+ blood vessels covered by pericytes in MC38, but not in CT26 tumors. This appears to occur because anti-GARP:TGF-ß1, by blocking TGF-ß1 signals, favors the proliferation of and expression of adhesion molecules such as E-selectin by blood endothelial cells. The resulting densification of intratumoral blood vasculature probably contributes to increased T cell infiltration and to the therapeutic efficacy of GARP:TGF-ß1/PD-1 blockade in MC38. We conclude from these distinct observations in MC38 and CT26, that the combined blockades of GARP:TGF-ß1 and PD-1 can exert anti-tumor activity via multiple mechanisms, including the densification and normalization of intratumoral blood vasculature, the increase of T cell infiltration into the tumor and the increase of the effector functions of intratumoral tumor-specific T cells. This may prove important for the selection of cancer patients who could benefit from combined GARP:TGF-ß1/PD-1 blockade in the clinics.

Engineering a Human Plasmacytoid Dendritic Cell-Based Vaccine to Prime and Expand Multispecific Viral and Tumor Antigen-Specific T-Cells.

Because dendritic cells are crucial to prime and expand antigen-specific CD8+ T-cells, several strategies are designed to use them in therapeutic vaccines against infectious diseases or cancer. In this context, off-the-shelf allogeneic dendritic cell-based platforms are more attractive than individualized autologous vaccines tailored to each patient. In the present study, a unique dendritic cell line (PDC*line) platform of plasmacytoid origin, already used to prime and expand antitumor immunity in melanoma patients, was improved thanks to retroviral engineering. We demonstrated that the clinical-grade PDC*line, transduced with genes encoding viral or tumoral whole proteins, efficiently processed and stably presented the transduced antigens in different human leukocyte antigen (HLA) class I contexts. Moreover, the use of polyepitope constructs allowed the presentation of immunogenic peptides and the expansion of specific cytotoxic effectors. We also demonstrated that the addition of the Lysosome-associated membrane protein-1 (LAMP-1) sequence greatly improved the presentation of some peptides. Lastly, thanks to transduction of new HLA molecules, the PDC platform can benefit many patients through the easy addition of matched HLA-I molecules. The demonstration of the effective retroviral transduction of PDC*line cells strengthens and broadens the scope of the PDC*line platform, which can be used in adoptive or active immunotherapy for the treatment of infectious diseases or cancer.

Paired Rheumatoid Arthritis Synovial Biopsies From Small and Large Joints Show Similar Global Transcriptomic Patterns With Enrichment of Private Specificity TCRB and TCR Signaling Pathways.

Objectives: We explored histological and transcriptomic profiles of paired synovial biopsies from rheumatoid arthritis (RA) patients, in order to assess homogeneity in synovial tissue at the individual level. Methods: Synovial biopsies were performed simultaneously in one small and one large joint per patient using needle-arthroscopy for the knee and ultrasound-guided biopsy for the hand or wrist. Synovium from individuals with osteoarthritis was used as controls. Paraffin-embedded samples were stained for CD3, CD20, and CD68. Total RNA was hybridized on high-density microarrays. TCRB variable sequences were obtained from synovial and blood RNA samples. Results: Twenty paired biopsies from 10 RA patients with active disease were analyzed. Semi-quantification of histological markers showed a positive correlation for synovial hyperplasia, inflammatory infiltrates and CD3-positive T cells between pairs. Pairwise comparison of transcriptomic profiles showed similar expression of RA-related molecular pathways (TCR signaling, T cell costimulation and response to TNFα). T cells clonotypes were enriched in all but one joints compared to blood, regardless of the magnitude of T cell infiltration. Enriched clonotypes were shared between pairs (23-100%), but this was less the case in pairs of joints displaying weaker T cell signatures and more pronounced germinal center-like transcriptomic profiles. Conclusion: Cellular and molecular alterations in RA synovitis are similar between small and large joints from the same patient. Interindividual differences in magnitude of T cell infiltrates and distribution of enriched T cell clonotypes support the concept of distinct synovial pathotypes in RA that are associated with systemic versus local antigen-driven activation of T cells.

Selective inhibition of TGF-ß1 produced by GARP-expressing Tregs overcomes resistance to PD-1/PD-L1 blockade in cancer.

TGF-ß1, ß2 and ß3 bind a common receptor to exert vastly diverse effects in cancer, supporting either tumor progression by favoring metastases and inhibiting anti-tumor immunity, or tumor suppression by inhibiting malignant cell proliferation. Global TGF-ß inhibition thus bears the risk of undesired tumor-promoting effects. We show that selective blockade of TGF-ß1 production by Tregs with antibodies against GARP:TGF-ß1 complexes induces regressions of mouse tumors otherwise resistant to anti-PD-1 immunotherapy. Effects of combined GARP:TGF-ß1/PD-1 blockade are immune-mediated, do not require FcγR-dependent functions and increase effector functions of anti-tumor CD8+ T cells without augmenting immune cell infiltration or depleting Tregs within tumors. We find GARP-expressing Tregs and evidence that they produce TGF-ß1 in one third of human melanoma metastases. Our results suggest that anti-GARP:TGF-ß1 mAbs, by selectively blocking a single TGF-ß isoform emanating from a restricted cellular source exerting tumor-promoting activity, may overcome resistance to PD-1/PD-L1 blockade in patients with cancer.

An innovative plasmacytoid dendritic cell line-based cancer vaccine primes and expands antitumor T-cells in melanoma patients in a first-in-human trial.

The efficacy of immune checkpoint inhibitors has been shown to depend on preexisting antitumor immunity; thus, their combination with cancer vaccines is an attractive therapeutic approach. Plasmacytoid dendritic cells (PDC) are strong inducers of antitumor responses and represent promising vaccine candidates. We developed a cancer vaccine approach based on an allogeneic PDC line that functioned as a very potent antigen-presenting cell in pre-clinical studies. In this phase Ib clinical trial, nine patients with metastatic stage IV melanoma received up to 60 million irradiated PDC line cells loaded with 4 melanoma antigens, injected subcutaneously at weekly intervals. The primary endpoints were safety and tolerability. The vaccine was well tolerated and no serious vaccine-induced side effects were recorded. Strikingly, there was no allogeneic response toward the vaccine, but a significant increase in the frequency of circulating anti-tumor specific T lymphocytes was observed in two patients, accompanied by a switch from a naïve to memory phenotype, thus demonstrating priming of antigen-specific T-cells. Signs of clinical activity were observed, including four stable diseases according to IrRC and vitiligoïd lesions. Four patients were still alive at week 48. We also demonstrate the in vitro enhancement of specific T cell expansion induced by the synergistic combination of peptide-loaded PDC line with anti-PD-1, as compared to peptide-loaded PDC line alone. Taken together, these clinical observations demonstrate the ability of the PDC line based-vaccine to prime and expand antitumor CD8+ responses in cancer patients. Further trials should test the combination of this vaccine with immune checkpoint inhibitors.

Toll-like receptor 3 increases antigen-presenting cell responses to a pro-apoptotic stimulus, yet does not contribute to systemic lupus erythematosus genetic susceptibility.

OBJECTIVES: TLR3 mediates skin solar injury by binding nuclear material released from apoptotic keratinocytes, resulting in the production of pro-inflammatory cytokines. Because the TLR3 gene is located in 4q35, a known systemic lupus erythematosus (SLE) susceptibility locus, we wondered whether TLR3 single nucleotide polymorphisms (SNPs) were associated with inflammatory mechanisms relevant to the development of SLE, and disease susceptibility. METHODS: Functional assays were carried out in TLR3-transfected HEK293 cells and in monocyte-derived dendritic cells (moDCs). TLR3 and IFNß immunofluorescence studies were performed in skin samples from 7 SLE patients and 3 controls. We performed a SNP association study in a discovery cohort of 153 patients and 105 controls, followed by a confirmation study in an independent cohort of 1,380 patients and 2,104 controls. RESULTS: TLR3 and IFNß are overexpressed in SLE skin lesions. TLR3 overexpression in HEK293 cells amplifies their sensitivity to a pro-apoptotic stimulus. Taking advantage of a naturally occurring polymorphic TLR3 variant (rs3775291) that weakly versus strongly responds to poly I:C stimulation, we found that TLR3 is associated with amplified apoptotic responses, production of the Ro/SSA autoantigen and increased maturation of myeloid-derived dendritic cells (moDC) after exposure to UV irradiation. However, TLR3 SNPs are not associated with susceptibility to SLE in a large population of patients and controls. CONCLUSIONS: TLR3 is overexpressed in SLE skin lesions and amplifies apoptotic and inflammatory responses to UV-irradiation in antigen-presenting cells in vitro. However, TLR3 SNPs do not impact susceptibility to the development of the disease.

Intraoperative ketorolac in high-risk breast cancer patients. A prospective, randomized, placebo-controlled clinical trial.

BACKGROUND: Ketorolac has been associated with a lower risk of recurrence in retrospective studies, especially in patients with positive inflammatory markers. It is still unknown whether a single dose of pre-incisional ketorolac can prolong recurrence-free survival. METHODS: The KBC trial is a multicenter, placebo-controlled, randomized phase III trial in high-risk breast cancer patients powered for 33% reduction in recurrence rate (from 60 to 40%). Patients received one dose of ketorolac tromethamine or a placebo before surgery. Eligible patients were breast cancer patients, planned for curative surgery, and with a Neutrophil-to-Lymphocyte Ratio≥4, node-positive disease or a triple-negative phenotype. The primary endpoint was Disease-Free Survival (DFS) at two years. Secondary endpoints included safety, pain assessment and overall survival. FINDINGS: Between February 2013 and July 2015, 203 patients were assigned to ketorolac (n = 96) or placebo (n = 107). Baseline characteristics were similar between arms. Patients had a mean age of 55.7 (SD14) years. At two years, 83.1% of the patients were alive and disease free in the ketorolac vs. 89.7% in the placebo arm (HR: 1.23; 95%CI: 0.65-2.31) and, respectively, 96.8% vs. 98.1% were alive (HR: 1.09; 95%CI: 0.34-3.51). CONCLUSIONS: A single administration of 30 mg of ketorolac tromethamine before surgery does not increase disease-free survival in high risk breast cancer patients. Overall survival difference between ketorolac tromethamine group and placebo group was not statistically significant. The study was however underpowered because of lower recurrence rates than initially anticipated. No safety concerns were observed. TRIAL REGISTRATION: ClinicalTrials.gov NCT01806259.

DNA alteration-based classification of uveal melanoma gives better prognostic stratification than immune infiltration, which has a neutral effect in high-risk group.

BACKGROUND: In uveal melanomas, immune infiltration is a marker of poor prognosis. This work intended to decipher the biological characteristics of intra-tumor immune population, compare it to other established biomarkers and to patients' outcome. METHODS: Primary, untreated, and mainly large uveal melanomas with retinal detachment were analyzed using: transcriptomic profiling (n = 15), RT-qPCR (n = 36), immunohistochemistry (n = 89), Multiplex Ligation-dependent Probe Amplification (MLPA) for copy number alterations (CNA) analysis (n = 89), array-CGH (n = 17), and survival statistics (n = 86). RESULTS: Gene expression analysis divided uveal melanomas into two groups, according to the IFNγ/STAT1-IRF1 pathway activation. Tumors with IFNγ-signature had poorer prognosis and showed increased infiltration of CD8+ T lymphocytes and macrophages. Cox multivariate analyses of immune cell infiltration with MLPA data delineated better prognostic value for three prognostic groups (three-tier stratification) than two (two-tier stratification). CNA-based model comprising monosomy 3, 8q amplification, and LZTS1and NBL1 deletions emerged as the best predictor for disease-free survival. It outperformed immune cell infiltration in receiver operating characteristic curves. The model that combined CNA and immune infiltration defined risk-groups according to the number of DNA alterations. Immune cell infiltration was increased in the high-risk group (73.7%), where it did not correlate with patient survival, while it was associated with poorer outcome in the intermediate risk-group. CONCLUSIONS: High degree of immune cell infiltration occurs in a subset of uveal melanomas, is interferon-gamma-related, and associated with poor survival. It allows for two-tier stratification, which is prognostically less efficient than a three-tier one. The best prognostic stratification is by CNA model with three risk-groups where immune cell infiltration impacts only some subgroups.

Characterization of two new high-grade B-cell lymphoma cell lines with MYC and BCL2 rearrangements that are suitable for in vitro drug sensitivity studies.

High-grade B-cell lymphomas with MYC and BCL2 or BCL6 rearrangements are highly aggressive B-cell lymphomas called double-hit lymphomas (HGBL-DH). They are particularly refractory to standard treatments and carry a poor prognosis. Fragments of resected tumoral lymph nodes from two HGBL-DH patients were put in culture. Continuously proliferating cells were characterized and compared with the original tumors. In both cases, the proliferating cells and the tumor displayed MYC and BCL2 rearrangements. Both cell lines (called LB5848-LYMP and LB5871-LYMP) presented a high proliferation rate and were maintained in culture for more than one year. Upon injection in immunodeficient mice, LB5848-LYMP gave rise to lymphoid tumors. In vitro treatment of these cell lines with a BCL2-inhibitory drug (ABT-199) selectively stopped their proliferation. These new cell lines represent valuable tools for studying HGBL-DH and for the in vitro testing of candidate therapies targeting HGBL-DH. LB5848-LYMP is also suitable for similar experiments in vivo.

Structural basis of latent TGF-ß1 presentation and activation by GARP on human regulatory T cells.

Transforming growth factor-ß1 (TGF-ß1) is one of very few cytokines produced in a latent form, requiring activation to exert any of its vastly diverse effects on development, immunity, and cancer. Regulatory T cells (Tregs) suppress immune cells within close proximity by activating latent TGF-ß1 presented by GARP (glycoprotein A repetitions predominant) to integrin αVß8 on their surface. We solved the crystal structure of GARP:latent TGF-ß1 bound to an antibody that stabilizes the complex and blocks release of active TGF-ß1. This finding reveals how GARP exploits an unusual medley of interactions, including fold complementation by the amino terminus of TGF-ß1, to chaperone and orient the cytokine for binding and activation by αVß8. Thus, this work further elucidates the mechanism of antibody-mediated blockade of TGF-ß1 activation and immunosuppression by Tregs.

Blocking immunosuppression by human Tregs in vivo with antibodies targeting integrin αVß8.

Human regulatory T cells (Tregs) suppress other T cells by converting the latent, inactive form of TGF-ß1 into active TGF-ß1. In Tregs, TGF-ß1 activation requires GARP, a transmembrane protein that binds and presents latent TGF-ß1 on the surface of Tregs stimulated through their T cell receptor. However, GARP is not sufficient because transduction of GARP in non-Treg T cells does not induce active TGF-ß1 production. RGD-binding integrins were shown to activate TGF-ß1 in several non-T cell types. Here we show that αVß8 dimers are present on stimulated human Tregs but not in other T cells, and that antibodies against αV or ß8 subunits block TGF-ß1 activation in vitro. We also show that αV and ß8 interact with GARP/latent TGF-ß1 complexes in human Tregs. Finally, a blocking antibody against ß8 inhibited immunosuppression by human Tregs in a model of xenogeneic graft-vs.-host disease induced by the transfer of human T cells in immunodeficient mice. These results show that TGF-ß1 activation on the surface of human Tregs implies an interaction between the integrin αVß8 and GARP/latent TGF-ß1 complexes. Immunosuppression by human Tregs can be inhibited by antibodies against GARP or against the integrin ß8 subunit. Such antibodies may prove beneficial against cancer or chronic infections.

Integrating Next-Generation Dendritic Cell Vaccines into the Current Cancer Immunotherapy Landscape.

Cancer immunotherapy is experiencing a renaissance spearheaded by immune checkpoint inhibitors (ICIs). This has spurred interest in 'upgrading' existing immunotherapies that previously experienced only sporadic success, such as dendritic cells (DCs) vaccines. In this review, we discuss the major molecular, immunological, and clinical determinants of existing first- and second-generation DC vaccines. We also outline the future trends for next-generation DC vaccines and describe their major hallmarks and prerequisites necessary for high anticancer efficacy. In addition, using existing data we compare DC vaccines with ICIs targeting CTLA4, PD1, and PD-L1, and argue that in various contexts next-generation DC vaccines are ready to meet some challenges currently confronting ICIs, thereby raising the need to integrate DC vaccines in future combinatorial immunotherapy regimens.

Cutting Edge: Active TGF-ß1 Released from GARP/TGF-ß1 Complexes on the Surface of Stimulated Human B Lymphocytes Increases Class-Switch Recombination and Production of IgA.

Production of active TGF-ß is regulated at a posttranslational level and implies release of the mature cytokine dimer from the inactive, latent TGF-ß precursor. There are several cell-type specific mechanisms of TGF-ß activation. We identified a new mechanism operating on the surface of human regulatory T cells and involving membrane protein GARP, which binds latent TGF-ß1. The paracrine activity of regulatory T cell-derived TGF-ß1 contributes to immunosuppression and can be inhibited with anti-GARP Abs. Whether other immune cell types use surface GARP to activate latent TGF-ß1 was not known. We show in this study that stimulated, human B lymphocytes produce active TGF-ß1 from surface GARP/latent TGF-ß1 complexes with isotype switching to IgA production.

A new transcript in the TCRB locus unveils the human ortholog of the mouse pre-Dß1 promoter.

INTRODUCTION: While most transcripts arising from the human T Cell Receptor locus reflect fully rearranged genes, several germline transcripts have been identified. We describe a new germline transcript arising from the human TCRB locus. METHODS: cDNA sequencing, promoter, and gene expression analyses were used to characterize the new transcript. RESULTS: The new germline transcript encoded by the human TCRB locus consists of a new exon of 103 bp, which we named TRBX1 (X1), spliced with the first exon of gene segments Cß1 or Cß2. X1 is located upstream of gene segment Dß1 and is therefore deleted from a V-DJ rearranged TCRB locus. The X1-Cß transcripts do not appear to code for a protein. We define their transcription start and minimal promoter. These transcripts are found in populations of mature T lymphocytes from blood or tissues and in T cell clones with a monoallelic TCRB rearrangement. In immature thymocytes, they are already detectable in CD1a- CD34+ CD4- CD8- cells, therefore before completion of the TCRB rearrangements. CONCLUSIONS: The X1 promoter appears to be the ortholog of the mouse pre-Dß1 promoter (PDß1). Like PDß1, its activation is regulated by Eß in T cells and might facilitate the TCRB rearrangement process by contributing to the accessibility of the Dß1 locus.