Double negative (DN) αβ T cells: misperception and overdue recognition

Phosphatidic Acid Promoting the Generation of Interleukin-17A Producing Double-Negative T Cells by Enhancing mTORC1 Signaling in Lupus

OBJECTIVE

The goal was to investigate the role and intracellular regulatory mechanisms of double-negative T (DNT) cells in the pathogenesis of systemic lupus erythematosus (SLE).

METHODS

DNT cells were assessed in murine models, patients with SLE, and controls using flow cytometry (FCM). DNT cells from either resiquimod (R848) or vehicle-treated C57BL/6 (B6) mice were cultured with B cells from R848-treated mice to explore functions. Differential mechanistic target of rapamycin (mTOR) pathway signaling in DNT cells measured using FCM and quantitative polymerase chain reaction was validated by rapamycin inhibition. Candidate lipid metabolites detected using liquid chromatography with electrospray ionization mass spectrometry/mass spectrometry were functionally assessed in DNT cell cultures.

RESULTS

DNT cells were markedly increased in both spontaneous and induced mouse lupus models and in patients with SLE. Expanded DNT cells from R848-treated B6 mice produced elevated interleukin (IL)-17A and IgG with increased germinal center B (GCB) cells. Expansion of DNT cells associated with activation of mTORC1 pathway that both IL-17A levels and the number of DNT cells exhibited dose-dependent reduction with rapamycin treatment. Lipidomics studies revealed differential patterns of lipid metabolites in T cells of R848-treated mice. Among candidate metabolites, elevated phosphatidic acid (PA) that was partially controlled by phospholipase D2 increased the expression of the mTORC1 downstream target p-S6 and positively expanded IL-17A-producing DNT cells. Similarly, elevated proportions of circulating DNT cells in patients with SLE correlated with disease activity and proteinuria, and IL-17A secretion was elevated after in vitro PA stimulation.

CONCLUSION

The accumulation of PA in T cells could activate the mTORC1 pathway, promoting DNT cell expansion and IL-17A secretion, resulting in GCB cell abnormalities in lupus.

Immune profiling analysis of double-negative T cells in patients with systemic sclerosis

OBJECTIVE

To construct a molecular immune map of patients with systemic sclerosis (SSc) by mass flow cytometry, and compare the number and molecular expression of double-negative T (DNT) cell subsets between patients and healthy controls (HC).

METHODS

Peripheral blood mononuclear cells (PBMCs) were extracted from the peripheral blood of 17 SSc patients and 9 HC. A 42-channel panel was set up to perform mass cytometry by time of flight (CyTOF) analysis for DNT subgroups. Flow cytometry was used to validate subpopulation functions. The clinical data of patients were collected for correlation analysis.

RESULTS

Compared with HC, the number of total DNT cells decreased in SSc patients. Six DNT subsets were obtained from CyTOF analysis, in which the proportion of cluster1 increased, while the proportion of cluster3 decreased. Further analysis revealed that cluster1 was characterized by high expression of CD28 and CCR7, and cluster3 was characterized by high expression of CD28 and CCR5. After in vitro stimulation, cluster1 secreted more IL-4 and cluster3 secreted more IL-10 in SSc patients compared to HC. Clinical correlation analysis suggested that cluster1 may play a pathogenic role while cluster3 may play a protective role in SSc. ROC curve analysis further revealed that cluster3 may be a potential indicator for determining disease activity in SSc patients.

CONCLUSION

We found a new CCR5+CD28+ DNT cell subset, which played a protective role in the pathogenesis of SSc. Key Points • The number of DNT cells decreased in SSc patients' peripheral blood. • DNT cells do not infiltrate in the skin but secrete cytokines to participate in the pathogenesis of SSc. • A CCR5+CD28+ DNT cell population may play a protective role in SSc.

Peripheral Blood Lymphocyte Subsets in Factor VIII Inhibitor-Positive Patients with Severe Hemophilia A: A Case-Control Study

INTRODUCTION AND OBJECTIVES

The present study aimed to investigate different peripheral lymphocyte subsets in patients with severe hemophilia A (HA) and factor VIII (FVIII) inhibitor production. For this, age-matched cases of 19 FVIII inhibitor-positive (IP), 21 FVIII inhibitor-negative (IN) and 45 healthy controls were selected for study.

METHODS

Flow cytometry was used to analyze the peripheral lymphocyte subsets, including T, B, natural killer (NK) and NKT cells. The T cell subsets included CD3 + CD4-CD8- [double negative T (DNT)], CD3 + CD4 + CD8+ [double-positive T (DPT)], CD3 + CD4 + CD8- and CD3 + CD4-CD8+ T cells. Pairwise comparisons of absolute lymphocyte subset values were conducted among the three groups. The cut-off value for absolute lymphocyte counts was determined using receiver operating characteristic curve analysis.

RESULTS

The results demonstrated that the absolute values of DPT cells in the IN and IP groups were significantly lower than those in the healthy control group (P = 0.007). The DNT values were also lower in severe HA patients with or without inhibitor than those in healthy subjects, but these differences were not statistically significant (P = 0.053). In addition, the absolute value of CD4+ Th cells in the IP group was lower than that in the healthy controls (P = 0.013). Although not statistically significant (P = 0.064), the absolute values of NKT cells were higher in the IN group compared with the IP group, and higher in the IP group compared with the healthy control group. There were no statistically significant differences in total T, B, CD8 + and NK cells among the IN, IP and healthy control groups. The cut-off value for absolute CD4+ Th cells in the IN group was < 598/µl.

CONCLUSION

The decrease in absolute values of CD4+ Th cells in severe HA patients may contribute to the establishment of infused FVIII immune tolerance. If the CD4+ Th value remains > 598/µl, clinicians should be vigilant for possible FVIII inhibitor production, especially on days prior to FVIII exposure.

CD138 promotes the accumulation and activation of autoreactive T cells in autoimmune MRL/lpr mice

Autoreactive T cells, specifically CD138+ (syndecan-1) T cells produced in Fas-deficient systemic lupus erythematosus (SLE) mouse models, were shown to significantly promote the generation of autoantibodies. In the present study, Murphy Roths Large lymphoproliferative (MRL/lpr) lupus mice were used to investigate the role of CD138 protein expression in T cells in the progression of SLE. Measurement of flow cytometry, immunofluorescence and Luminex were performed to determine the effect of CD138 on T cells in MRL/lpr mice. The results demonstrate that CD138+ T cells induce apoptosis via a Fas-dependent pathway. CD138 protein expression in T cells of MRL/lpr mice significantly reduced T cell apoptosis and contributed to the accumulation of T cells and double negative (DN) T cells, whilst simultaneously promoting T cell activation in Fas-deficient lupus mice. CD138 protein expression in DN T cells also significantly increased the protein expression of Fas ligand to enhance the cytotoxicity of DN T cells. Furthermore, phorbol 12-myristate 13-acetate and ionomycin (PI) stimulation reduced CD138 protein expression in CD3+ T cells and prevented CD138+ T cell accumulation by inducing specific apoptosis. PI stimulation also activated T cells in MRL/lpr mice to increase CD69 protein expression. CD69 protein expression in CD138+ T cells significantly increased the frequency of apoptotic CD138+ T cells. In addition, results from the present study demonstrated that CD138- T cells of MRL/lpr lupus mice had an activation defect. CD138 protein expression in T cells significantly reversed the defective activation and activating T cells could significantly reduce CD138 protein expression in CD3+ T cells of MRL/lpr mice. This suggests that CD138 protein expression in CD3+CD138- T cells of MRL/lpr mice may be a consequence of the impaired activation in autoreactive T cells prior to exposure to self-antigens by the immune system. CD138 expression in autoreactive T cells has a central role in promoting the progression and development of autoimmune response in MRL/lpr mice.

TFAP4 promotes the progression of liver fibrosis through regulating double-negative T cell differentiation via OX40

This work aimed to investigate the role of transcription factor TFAP4-OX40 in promoting the differentiation of double-negative T cells (DNTs). Through prediction and experimental analysis, it was discovered that TFAP4 was the transcription factor of OX40. Therefore, OX40 neutralizing antibody and TFAP4 overexpression transfection were adopted to investigate the role of TFAP4-OX40 in DNTs differentiation, and the effect of differentiated DNTs on hepatic stellate cell (HSC) activation. Moreover, the impact of TFAP4 on liver fibrosis and DNTs in liver tissue was explored using mice with myeloid specific TFAP4 knockout by TFAP4 neutralizing antibody treatment. TFAP4 is the transcription regulatory factor for OX40, which promoted OX40 transcription expression to accelerate DNTs differentiation. Treatment with OX40 neutralizing antibody suppressed DNTs differentiation, while TFAP4 overexpression promoted DNTs differentiation. DNTs produced from the TFAP4 induced differentiation promoted HSC activation. Myeloid specific TFAP4 knockout delayed the progression of liver fibrosis and decreased DNTs in tissue, while treatment with TFAP4 neutralizing antibody suppressed liver fibrosis and DNTs in liver tissue. According to our results, TFAP4 is the transcription factor of OX40, which promotes DNTs differentiation via the OX40 signal, thus promoting the progression of liver fibrosis.

Intracellular osteopontin protects from autoimmunity-driven lymphoma development inhibiting TLR9-MYD88-STAT3 signaling

BACKGROUND

Autoimmune disorders, including Systemic Lupus Erythematosus (SLE), are associated with increased incidence of hematological malignancies. The matricellular protein osteopontin (OPN) has been linked to SLE pathogenesis, as SLE patients show increased serum levels of OPN and often polymorphisms in its gene. Although widely studied for its pro-tumorigenic role in different solid tumours, the role of OPN in autoimmunity-driven lymphomagenesis has not been investigated yet.

METHODS

To test the role of OPN in the SLE-associated lymphomagenesis, the SLE-like prone Fas^lpr/lpr mutation was transferred onto an OPN-deficient background. Spleen from Fas^lpr/lpr and OPN-/-Fas^lpr/lpr mice, as well as purified B cells, were analysed by histopathology, flow cytometry, Western Blot, immunohistochemistry, immunofluorescence and gene expression profile to define lymphoma characteristics and investigate the molecular mechanisms behind the observed phenotype. OPN cellular localization in primary splenic B cells and mouse and human DLBCL cell lines was assessed by confocal microscopy. Finally, gain of function experiments, by stable over-expression of the secreted (sOPN) and intracellular OPN (iOPN) in OPN-/-Fas^lpr/lpr -derived DLBCL cell lines, were performed for further validation experiments.

RESULTS

Despite reduced autoimmunity signs, OPN-/-Fas^lpr/lpr mice developed splenic lymphomas with higher incidence than Fas^lpr/lpr counterparts. In situ and ex vivo analysis featured such tumours as activated type of diffuse large B cell lymphoma (ABC-DLBCL), expressing BCL2 and c-MYC, but not BCL6, with activated STAT3 signaling. OPN-/-Fas^lpr/lpr B lymphocytes showed an enhanced TLR9-MYD88 signaling pathway, either at baseline or after stimulation with CpG oligonucleotides, which mimic dsDNA circulating in autoimmune conditions. B cells from Fas^lpr/lpr mice were found to express the intracellular form of OPN. Accordingly, gene transfer-mediated re-expression of iOPN, but not of its secreted isoform, into ABC-DLBCL cell lines established from OPN-/-Fas^lpr/lpr mice, prevented CpG-mediated activation of STAT3, suggesting that the intracellular form of OPN may represent a brake to TLR9 signaling pathway activation.

CONCLUSION

These data indicate that, in the setting of SLE-like syndrome in which double strand-DNA chronically circulates and activates TLRs, B cell intracellular OPN exerts a protective role in autoimmunity-driven DLBCL development, mainly acting as a brake in the TLR9-MYD88-STAT3 signaling pathway.

EGR2 Deletion Suppresses Anti-DsDNA Autoantibody and IL-17 Production in Autoimmune-Prone B6/lpr Mice: A Differential Immune Regulatory Role of EGR2 in B6/lpr Versus Normal B6 Mice

Previous studies have reported that deletion of the transcription factor, early growth response protein 2 (EGR2), in normal C57BL/6 (B6) resulted in the development of lupus-like autoimmune disease. However, increased EGR2 expression has been noted in human and murine lupus, which challenges the notion of the autoimmune suppressive role of EGR2 in B6 mice. In this study, we derived both conditional EGR2^-/-B6/lpr and EGR2^-/-B6 mice to elucidate the immune and autoimmune regulatory roles of EGR2 in autoinflammation (B6/lpr) versus physiologically normal (B6) conditions. We found that conditional EGR2 deletion increased spleen weight, enhanced T cell activation and IFNγ production, and promoted germinal center B cells and LAG3⁺ regulatory T cells development in both B6/lpr and B6 mice. Nevertheless, EGR2 deletion also showed strikingly differential effects in these two strains on T lymphocyte subsets profile, Foxp3⁺ Tregs and plasma cell differentiation, anti-dsDNA autoantibodies and immunoglobulins production, and on the induction of IL-17 in in vitro activated splenocytes. Specifically, EGR2 deletion in B6/lpr mice significantly decreased serum levels of anti-dsDNA autoantibodies, total IgG, IgM, IgG1, and IgG2a with reduced plasma cells differentiation. Furthermore, EGR2 deletion in B6/lpr mice had no obvious effect on IgG immunocomplex deposition, medium caliber vessel, and glomeruli inflammation but increased complement C3 immunocomplex deposition and large caliber vessel inflammation in the kidneys. Importantly, we demonstrated that EGR2 deletion in B6/lpr mice significantly reduced pathogenic CD4^-CD8^-CD3⁺B220⁺ double negative T cells, which correlated with the reduced anti-dsDNA autoantibodies in serum and decreased IL-17 production in splenocytes of EGR2^-/-B6/lpr mice. Together, our data strongly suggest that the role of EGR2 is complex. The immunoregulatory role of EGR2 varies at normal or autoinflammation conditions and should not be generalized in differential experimental settings.

Glucocorticoid prevents CD138 expression in T cells of autoimmune MRL/lpr mice

CD138⁺ T cells, the majority of which are CD4 and CD8 double-negative (DN) T cells, contribute to the production of anti-dsDNA antibodies in a CD4 receptor-dependent way to promote the development of systemic lupus erythematosus (SLE). Accumulation of CD138⁺ T cells in the spleen of MRL/lpr mice was significantly reduced by prednisone. Reduced expression of CD138 in DN T cells induced by prednisone treatment alleviated the accumulation of DN T cells in MRL/lpr mice. The frequency of CD138⁺ cells in CD4⁺ T cells of prednisone-treated MRL/lpr mice was also significantly reduced, which subsequently contributed to reduced production of anti-dsDNA antibody in the prednisone-treated MRL/lpr mice. Additionally, prednisone significantly reduced serum IgG and IgG subsets and simultaneously increased IgM secretion in serum. This suggested that glucocorticoids played a protective role during SLE treatment in MRL/lpr mice by promoting the production of IgM. The present study provides new insights into the mechanism of glucocorticoid for the treatment of SLE.

CD3+CD4-CD8- (Double-Negative) T Cells in Inflammation, Immune Disorders and Cancer

The crucial role of CD4⁺ and CD8⁺ T cells in shaping and controlling immune responses during immune disease and cancer development has been well established and used to achieve marked clinical benefits. CD3⁺CD4^-CD8^- double-negative (DN) T cells, although constituting a rare subset of peripheral T cells, are gaining interest for their roles in inflammation, immune disease and cancer. Herein, we comprehensively review the origin, distribution and functions of this unique T cell subgroup. First, we focused on characterizing multifunctional DN T cells in various immune responses. DN regulatory T cells have the capacity to prevent graft-versus-host disease and have therapeutic value for autoimmune disease. T helper-like DN T cells protect against or promote inflammation and virus infection depending on the specific settings and promote certain autoimmune disease. Notably, we clarified the role of DN tumor-infiltrating lymphocytes and outlined the potential for malignant proliferation of DN T cells. Finally, we reviewed the recent advances in the applications of DN T cell-based therapy for cancer. In conclusion, a better understanding of the heterogeneity and functions of DN T cells may help to develop DN T cells as a potential therapeutic tool for inflammation, immune disorders and cancer.

Double-negative T cells: Setting the stage for disease control or progression

Double-negative (DN) T cells are present at relatively low frequencies in human peripheral blood, and are characterized as expressing the alpha-beta or gamma-delta T-cell receptor (TCR), but not the CD4 nor the CD8 co-receptors. Despite their low frequencies, these cells are potent producers of cytokines and, thus, are key orchestrators of immune responses. DN T cells were initially associated with induction of peripheral immunological tolerance and immunomodulatory activities related to disease prevention. However, other studies demonstrated that these cells can also display effector functions associated with pathology development. This apparent contradiction highlighted the heterogeneity of the DN T-cell population. Here, we review phenotypic and functional characteristics of DN T cells, emphasizing their role in human diseases. The need for developing biomarkers to facilitate the translation of studies from animal models to humans will also be discussed. Finally, we will examine DN T cells as promising therapeutic targets to prevent or inhibit human disease development.

Application of double-negative T cells in haematological malignancies: recent progress and future directions

Haematologic malignancies account for a large proportion of cancers worldwide. The high occurrence and mortality of haematologic malignancies create a heavy social burden. Allogeneic haematopoietic stem cell transplantation is widely used in the treatment of haematologic malignancies. However, graft-versus-host disease and relapse after allogeneic haematopoietic stem cell transplantation are inevitable. An emerging treatment method, adoptive cellular therapy, has been effectively used in the treatment of haematologic malignancies. T cells, natural killer (NK) cells and tumour-infiltrating lymphocytes (TILs) all have great potential in therapeutic applications, and chimeric antigen receptor T (CAR-T) cell therapy especially has potential, but cytokine release syndrome and off-target effects are common. Efficient anticancer measures are urgently needed. In recent years, double-negative T cells (CD3⁺CD4^-CD8^-) have been found to have great potential in preventing allograft/xenograft rejection and inhibiting graft-versus-host disease. They also have substantial ability to kill various cell lines derived from haematologic malignancies in an MHC-unrestricted manner. In addition, healthy donor expanded double-negative T cells retain their antitumour abilities and ability to inhibit graft-versus-host disease after cryopreservation under good manufacturing practice (GMP) conditions, indicating that double-negative T cells may be able to be used as an off-the-shelf product. In this review, we shed light on the potential therapeutic ability of double-negative T cells in treating haematologic malignancies. We hope to exploit these cells as a novel therapy for haematologic malignancies.

Imprint of unconventional T-cell response in acute hepatitis C persists despite successful early antiviral treatment

Unconventional T cells (UTCs) are a heterogeneous group of T cells that typically exhibit rapid responses toward specific antigens from pathogens. Chronic hepatitis C virus (HCV) infection causes dysfunction of several subsets of UTCs. This altered phenotype and function of UTCs can persist over time even after direct-acting antiviral (DAA)-mediated clearance of chronic HCV. However, it is less clear if and how UTCs respond in acute, symptomatic HCV infection, a rare clinical condition, and if rapid DAA treatment of such patients reverses the caused perturbations within UTCs. Here, we comprehensively analyzed the phenotype and reinvigoration capacity of three major UTC populations, mucosal-associated invariant T (MAIT) cells, γδ T cells, and CD4 and CD8 double-negative αβ T cells (DNT cells) before, during, and after DAA-mediated clearance of acute symptomatic HCV infection. Furthermore, MAIT cell functionality was systematically studied. We observed a reduced frequency of MAIT cells. However, remaining cells presented with a near-to-normal phenotype in acute infection, which contrasted with a significant dysfunction upon stimulation that was not restored after viral clearance. Notably, DNT and γδ T cells displayed a strong activation ex-vivo in acute HCV infection, which subsequently normalized during the treatment. In addition, DNT cell activation was specifically associated with liver inflammation and inflammatory cytokines. Altogether, these data provide evidence that UTCs respond in a cell type-specific manner during symptomatic HCV infection. However, even if early treatment is initiated, long-lasting imprints within UTCs remain over time.

Transcriptomic Profiling of Collagenous Colitis Identifies Hallmarks of Nondestructive Inflammatory Bowel Disease

BACKGROUND AND AIMS

The pathophysiology of the inflammatory bowel disease collagenous colitis (CC) is poorly described. Our aim was to use RNA sequencing of mucosal samples from patients with active CC, CC in remission, refractory CC, ulcerative colitis (UC), and control subjects to gain insight into CC pathophysiology, identify genetic signatures linked to CC, and uncover potentially druggable disease pathways.

METHODS

We performed whole transcriptome sequencing of CC samples from patients before and during treatment with the corticosteroid drug budesonide, CC steroid-refractory patients, UC patients, and healthy control subjects (n = 9-13). Bulk mucosa and laser-captured microdissected intestinal epithelial cell (IEC) gene expression were analyzed by gene set enrichment and gene set variation analyses to identify significant pathways and cells, respectively, altered in CC. Leading genes and cells were validated using reverse-transcription quantitative polymerase chain reaction or immunohistochemistry.

RESULTS

We identified an activation of the adaptive immune response to bacteria and viruses in active CC that could be mediated by dendritic cells. Moreover, IECs display hyperproliferation and increased antigen presentation in active CC. Further analysis revealed that genes related to the immune response (DUOX2, PLA2G2A, CXCL9), DNA transcription (CTR9), protein processing (JOSD1, URI1), and ion transport (SLC9A3) remained dysregulated even after budesonide-induced remission. Budesonide-refractory CC patients fail to restore normal gene expression, and displayed a transcriptomic profile close to UC.

CONCLUSIONS

Our study confirmed the implication of innate and adaptive immune responses in CC, governed by IECs and dendritic cells, respectively, and identified ongoing epithelial damage. Refractory CC could share pathomechanisms with UC.

The Potential of Harnessing IL-2-Mediated Immunosuppression to Prevent Pathogenic B Cell Responses

Immunosuppressive drugs can partially control Antibody (Ab)-dependent pathology. However, these therapeutic regimens must be maintained for the patient's lifetime, which is often associated with severe side effects. As research advances, our understanding of the cellular and molecular mechanisms underlying the development and maintenance of auto-reactive B cell responses has significantly advanced. As a result, novel immunotherapies aimed to restore immune tolerance and prevent disease progression in autoimmune patients are underway. In this regard, encouraging results from clinical and preclinical studies demonstrate that subcutaneous administration of low-doses of recombinant Interleukin-2 (r-IL2) has potent immunosuppressive effects in patients with autoimmune pathologies. Although the exact mechanism by which IL-2 induces immunosuppression remains unclear, the clinical benefits of the current IL-2-based immunotherapies are attributed to its effect on bolstering T regulatory (Treg) cells, which are known to suppress overactive immune responses. In addition to Tregs, however, rIL-2 also directly prevent the T follicular helper cells (Tfh), T helper 17 cells (Th17), and Double Negative (DN) T cell responses, which play critical roles in the development of autoimmune disorders and have the ability to help pathogenic B cells. Here we discuss the broader effects of rIL-2 immunotherapy and the potential of combining rIL-2 with other cytokine-based therapies to more efficiently target Tfh cells, Th17, and DN T cells and subsequently inhibit auto-antibody (ab) production in autoimmune patients.

Immune checkpoint deficiencies and autoimmune lymphoproliferative syndromes

Autoimmune lymphoproliferative syndrome (ALPS) is an inherited non-malignant and non-infectious lymphoproliferative syndrome caused by mutations in genes affecting the extrinsic apoptotic pathway (FAS, FASL, CASP10). The resulting FAS-mediated apoptosis defect accounts for the expansion and accumulation of autoreactive (double-negative) T cells leading to cytopenias, splenomegaly, lymphadenopathy, autoimmune disorders, and risk of lymphoma. However, there are other monogenetic disorders known as ALPS-like syndromes that can be clinically similar to ALPS but are genetically and biologically different, such as observed in patients with immune checkpoint deficiencies, particularly cytotoxic T-lymphocyte antigen 4 (CTLA-4) insufficiency and lipopolysaccharide-responsive beige-like anchor protein LRBA deficiency. CTLA-4 insufficiency is caused by heterozygous mutations in CTLA-4, an essential negative immune regulator that is constitutively expressed on regulatory T (Treg) cells. Mutations in CTLA-4 affect CTLA-4 binding to CD80-CD86 costimulatory molecules, CTLA-4 homodimerization, or CTLA-4 intracellular vesicle trafficking upon cell activation. Abnormal CTLA-4 trafficking is also observed in patients with LRBA deficiency, a syndrome caused by biallelic mutations in LRBA that abolishes the LRBA protein expression. Both immune checkpoint deficiencies are biologically characterized by low levels of CTLA-4 protein on the cell surface of Tregs, accounting for the autoimmune manifestations observed in CTLA4-insufficient and LRBA-deficient patients. In addition, both immune checkpoint deficiencies present with an overlapping but heterogeneous clinical picture despite the difference in inheritance and penetrance. In this review, we describe the most prominent clinical features of ALPS, CTLA-4 insufficiency and LRBA deficiency, emphasizing their corresponding biological mechanisms. We also provide some clinical and laboratory approaches to diagnose these three rare immune disorders, together with therapeutic strategies that have worked best at improving prognosis and quality life of patients.

SH3BP2 Deficiency Ameliorates Murine Systemic Lupus Erythematosus

BACKGROUND

The adaptor protein Src homology 3 domain-binding protein 2 (SH3BP2) is widely expressed in immune cells. It controls intracellular signaling pathways. The present study was undertaken to investigate the role of SH3BP2 in a murine systemic lupus erythematosus model.

METHODS

For the lupus model, we used Fas^lpr/lpr mice. Clinical and immunological phenotypes were compared between Fas^lpr/lpr and SH3BP2-deficient Fas^lpr/lpr mice. Splenomegaly and renal involvement were assessed. Lymphocyte subsets in the spleen were analyzed by flow cytometry. To examine the role of SH3BP2 in specific cells, B cell-specific SH3BP2-deficient lupus mice were analyzed; T cells and bone marrow-derived dendritic cells and macrophages were analyzed in vitro.

RESULTS

SH3BP2 deficiency significantly reduced lupus-like phenotypes, presented as splenomegaly, renal involvement, elevated serum anti-dsDNA antibody, and increased splenic B220⁺CD4^-CD8^- T cells. Notably, SH3BP2 deficiency in B cells did not rescue the lupus-like phenotypes. Furthermore, SH3BP2 deficiency did not substantially affect the characteristics of T cells and macrophages in vitro. Interestingly, SH3BP2 deficiency suppressed the differentiation of dendritic cells in vitro and reduced the number of dendritic cells in the spleen of the lupus-prone mice.

CONCLUSIONS

SH3BP2 deficiency ameliorated lupus-like manifestations. Modulating SH3BP2 expression could thus provide a novel therapeutic approach to autoimmune diseases.

Distinct cellular immune profiles in the airways and blood of critically ill patients with COVID-19

Background

Knowledge of the pathophysiology of COVID-19 is almost exclusively derived from studies that examined the immune response in blood. We here aimed to analyse the pulmonary immune response during severe COVID-19 and to compare this with blood responses.

Methods

This was an observational study in patients with COVID-19 admitted to the intensive care unit (ICU). Mononuclear cells were purified from bronchoalveolar lavage fluid (BALF) and blood, and analysed by spectral flow cytometry; inflammatory mediators were measured in BALF and plasma.

Findings

Paired blood and BALF samples were obtained from 17 patients, four of whom died in the ICU. Macrophages and T cells were the most abundant cells in BALF, with a high percentage of T cells expressing the ƴδ T cell receptor. In the lungs, both CD4 and CD8 T cells were predominantly effector memory cells (87·3% and 83·8%, respectively), and these cells expressed higher levels of the exhaustion marker programmad death-1 than in peripheral blood. Prolonged ICU stay (>14 days) was associated with a reduced proportion of activated T cells in peripheral blood and even more so in BALF. T cell activation in blood, but not in BALF, was higher in fatal COVID-19 cases. Increased levels of inflammatory mediators were more pronounced in BALF than in plasma.

Interpretation

The bronchoalveolar immune response in COVID-19 has a unique local profile that strongly differs from the immune profile in peripheral blood. Fully elucidating COVID-19 pathophysiology will require investigation of the pulmonary immune response.

Fas/FasL Signaling Regulates CD8 Expression During Exposure to Self-Antigens

Activation of self-reactive CD8+ T cells induces a peripheral tolerance mechanism that involves loss of CD8 expression. Because genetic deficiency of Fas and Fasl causes the accumulation of double-negative (DN; CD3+ TCR-αβ+ CD4- CD8-) T cells that have been proposed to derive from CD8+ cells, we decided to explore the role of Fas and FasL in self-antigen-induced CD8 downregulation. To this end, we quantified Fas and FasL induction by different stimuli and analyzed the effects of Fas/FasL deficiency during a protective immune response and after exposure to self-antigens. Our data describes how Fas and FasL upregulation differs depending on the setting of CD8 T cell activation and demonstrates that Fas/FasL signaling maintains CD8 expression during repetitive antigen stimulation and following self-antigen encounter. Together, our results reveal an unexpected role of Fas/FasL signaling and offer a new insight into the role of these molecules in the regulation of immune tolerance.

Evidence of genetic epistasis in autoimmune diabetes susceptibility revealed by mouse congenic sublines

Susceptibility to autoimmune diabetes is a complex genetic trait. Linkage analyses exploiting the NOD mouse, which spontaneously develops autoimmune diabetes, have proved to be a useful tool for the characterization of some of these traits. In a linkage analysis using 3A9 TCR transgenic mice on both B10.BR and NOD.H2^k backgrounds, we previously determined that both the Idd2 and Idd13 loci were linked to the proportion of immunoregulatory CD4^-CD8^- double negative (DN) T cells. In addition to Idd2 and Idd13, five other loci showed weak linkage to the proportion of DN T cells. Of interest, in an interim analysis, a locus on chromosome 12 is linked to DN T cell proportion in both the spleen and the lymph nodes. To determine the impact of this locus on DN T cells, we generated two congenic sublines, which we named Chr12P and Chr12D for proximal and distal, respectively. While 3A9 TCR:insHEL NOD.H2^k-Chr12D mice were protected from diabetes, 3A9 TCR:insHEL NOD.H2^k-Chr12P showed an increase in diabetes incidence. Yet, the proportion of DN T cells was similar to the parental 3A9 TCR NOD.H2^k strain for both of these congenic sublines. A genome-wide two dimensional LOD score analysis reveals genetic epistasis between chromosome 12 and the Idd13 locus. Altogether, this study identified further complex genetic interactions in defining the proportion of DN T cells, along with evidence of genetic epistasis within a locus on chromosome 12 influencing autoimmune susceptibility.

Double-negative T cells in autoimmune diseases

PURPOSE OF REVIEW

TCRαβ+CD4-CD8- double-negative T (DNT) cells, a principal subset of mature T lymphocytes, have been closely linked with autoimmune/inflammatory conditions. However, controversy persists regarding their ontogeny and function. Here, we present an overview on DNT cells in different autoimmune diseases to advance a deeper understanding of the contribution of this population to disease pathogenesis.

RECENT FINDINGS

DNT cells have been characterized in various chronic inflammatory diseases and they have been proposed to display pathogenic or regulatory function. The tissue location of DNT cells and the effector cytokines they produce bespeak to their active involvement in chronic inflammatory diseases.

SUMMARY

By producing various cytokines, expanded DNT cells in inflamed tissues contribute to the pathogenesis of a variety of autoimmune inflammatory diseases. However, it is unclear whether this population represents a stable lineage consisting of different subsets similar to CD4+ T helper cell subset. Better understanding of the possible heterogeneity and plasticity of DNT cells is needed to reveal interventional therapeutic opportunities.

CD3+CD4-CD8- Double-negative αβ T cells attenuate lung ischemia-reperfusion injury

OBJECTIVE

Lung ischemia-reperfusion injury (IRI) is a common complication after lung transplantation, and immune cells have been implicated in modulating outcomes. We hypothesized that a newly described subset of αβ T-cell receptor positive cells; that is, CD4-CD8- (double negative [DN]) T cells, are found in lungs and can protect against lung IRI.

METHODS

Ischemia was induced in C57BL/6 mice by left pulmonary artery and vein occlusion for 30 minutes followed by 180 minutes of reperfusion. These mice were paired with sham hilar dissected surgical controls. In mice undergoing IRI, adoptive transfer of DN T cells or conventional T cells was performed 12 hours before occlusion. Flow cytometry was used to quantify T cells and inflammatory cytokines, and apoptotic signaling pathways were evaluated with immunoblotting. Lung injury was assessed with Evans blue dye extravasation.

RESULTS

DN T cells were significantly higher (5.29% ± 1% vs 2.21% ± 3%; P < .01) in IRI lungs and secreted higher levels of interleukin-10 (30% ± 5% vs 6% ± 1%; P < .01) compared with surgical sham controls. Immunoblotting, hematoxylin and eosin staining and Evans blue dye demonstrated that adoptive transfer of DN T cells significantly decreased interstitial edema (P < .01) and attenuated apoptosis/cleaved caspase-3 expression in the lungs following lung IRI (P < .01).

CONCLUSIONS

DN T cells traffic into lungs during IRI, and have tissue protective functions regulating inflammation and apoptosis. We propose a potential novel immunoregulatory function of DN T cells during lung IRI.

Metformin enhances the immunomodulatory potential of adipose-derived mesenchymal stem cells through STAT1 in an animal model of lupus

OBJECTIVES

Mesenchymal stem cells (MSCs) are considered potential therapeutic agents for treating autoimmune disease because of their immunomodulatory capacities and anti-inflammatory effects. However, several studies have shown that there is no consistency in the effectiveness of the MSCs to treat autoimmune disease, including SLE. In this study, we investigated whether metformin could enhance the immunoregulatory function of MSCs, what mechanism is relevant, and whether metformin-treated MSCs could be effective in an animal lupus model.

METHODS

Adipose-derived (Ad)-MSCs were cultured for 72 h in the presence of metformin. Immunoregulatory factors expression was analysed by real-time PCR and ELISA. MRL/lpr mice weekly injected intravenously with 1 × 106 Ad-MSCs or metformin-treated Ad-MSCs for 8 weeks. 16-week-old mice were sacrificed and proteinuria, anti-dsDNA IgG antibody, glomerulonephritis, immune complex, cellular subset were analysed in each group.

RESULTS

Metformin enhanced the immunomodulatory functions of Ad-MSCs including IDO, IL-10 and TGF-β. Metformin upregulated the expression of p-AMPK, p-STAT1 and inhibited the expression of p-STAT3, p-mTOR in Ad-MSCs. STAT1 inhibition by siRNA strongly diminished IDO, IL-10, TGF-β in metformin-treated Ad-MSCs. As a result, metformin promoted the immunoregulatory effect of Ad-MSCs by enhancing STAT1 expression, which was dependent on the AMPK/mTOR pathway. Administration of metformin-treated Ad-MSCs resulted in significant disease activity improvement including inflammatory phenotype, glomerulonephritis, proteinuria and anti-dsDNA IgG antibody production in MRL/lpr mice. Moreover, metformin-treated Ad-MSCs inhibited CD4-CD8- T-cell expansion and Th17/Treg cell ratio.

CONCLUSION

Metformin optimized the immunoregulatory properties of Ad-MSCs and may be a novel therapeutic agent for the treatment of lupus.

The epididymal immune balance: a key to preserving male fertility

Up to 15% of male infertility has an immunological origin, either due to repetitive infections or to autoimmune responses mainly affecting the epididymis, prostate, and testis. Clinical observations and epidemiological data clearly contradict the idea that the testis confers immune protection to the whole male genital tract. As a consequence, the epididymis, in which posttesticular spermatozoa mature and are stored, has raised some interest in recent years when it comes to its immune mechanisms. Indeed, sperm cells are produced at puberty, long after the establishment of self-tolerance, and they possess unique surface proteins that cannot be recognized as self. These are potential targets of the immune system, with the risk of inducing autoantibodies and consequently male infertility. Epididymal immunity is based on a finely tuned equilibrium between efficient immune responses to pathogens and strong tolerance to sperm cells. These processes rely on incompletely described molecules and cell types. This review compiles recent studies focusing on the immune cell types populating the epididymis, and proposes hypothetical models of the organization of epididymal immunity with a special emphasis on the immune response, while also discussing important aspects of the epididymal immune regulation such as tolerance and tumour control.

Systemic lupus erythematosus favors the generation of IL-17 producing double negative T cells

Mature double negative (DN) T cells are a population of αβ T cells that lack CD4 and CD8 coreceptors and contribute to systemic lupus erythematosus (SLE). The splenic marginal zone macrophages (MZMs) are important for establishing immune tolerance, and loss of their number or function contributes to the progression of SLE. Here we show that loss of MZMs impairs the tolerogenic clearance of apoptotic cells and alters the serum cytokine profile, which in turn provokes the generation of DN T cells from self-reactive CD8⁺ T cells. Increased Ki67 expression, narrowed TCR V-beta repertoire usage and diluted T-cell receptor excision circles confirm that DN T cells from lupus-prone mice and patients with SLE undergo clonal proliferation and expansion in a self-antigen dependent manner, which supports the shared mechanisms for their generation. Collectively, our results provide a link between the loss of MZMs and the expansion of DN T cells, and indicate possible strategies to prevent the development of SLE.

Splenic marginal zone macrophages can establish immune tolerance and limit the development of systemic lupus erythematosus (SLE). Here the authors show that these cells do this by clearing apoptotic cells, and defects in these cells result in the generation of self-reactive double negative T cells that are known to contribute to SLE pathogenesis.

MHC-Independent Thymic Selection of CD4 and CD8 Coreceptor Negative αβ T Cells

It is becoming increasingly clear that unconventional T cell subsets, such as NKT, γδ T, mucosal-associated invariant T, and CD8αα T cells, each play distinct roles in the immune response. Subsets of these cell types can lack both CD4 and CD8 coreceptor expression. Beyond these known subsets, we identify CD4^-CD8^-TCRαβ⁺, double-negative (DN) T cells, in mouse secondary lymphoid organs. DN T cells are a unique unconventional thymic-derived T cell subset. In contrast to CD5^high DN thymocytes that preferentially yield TCRαβ⁺ CD8αα intestinal lymphocytes, we find that mature CD5^low DN thymocytes are precursors to peripheral DN T cells. Using reporter mouse strains, we show that DN T cells transit through the immature CD4⁺CD8⁺ (double-positive) thymocyte stage. Moreover, we provide evidence that DN T cells can differentiate in MHC-deficient mice. Our study demonstrates that MHC-independent thymic selection can yield DN T cells that are distinct from NKT, γδ T, mucosal-associated invariant T, and CD8αα T cells.

Inhibition of Histone Deacetylase (HDAC) Enhances Checkpoint Blockade Efficacy by Rendering Bladder Cancer Cells Visible for T Cell-Mediated Destruction

Inhibitory checkpoint blockade therapy is an immunomodulatory strategy that results in the restoration of T cell functions, and its efficacy depends on the recognition of tumor cells for destruction. Considering the factors at play, one could propose that anti-tumor responses will not occur if tumor cells are immunologically invisible to T cells. In this study, we tested a strategy based on the modulation of cancer cell's immunovisibility through HDAC inhibition. In a model (heterotopic and orthotopic) of mouse urothelial bladder cancer, we demonstrated that the use of intratumoral or intravesical HDACi in combination with systemic anti-PD-1 was effective at inducing curative responses with durable anti-tumor immunity capable of preventing tumor growth at a distal site. Mechanistically, we determined that protective responses were dependent on CD8 cells, but not NK cells. Of significance, in an in vitro human model, we found that fully activated T cells fail at killing bladder cancer cells unless tumor cells were pretreated with HDACi. Complementary to this observation, we found that HDACi cause gene deregulation, that results in the upregulation of genes responsible for mediating immunorecognition, NKG2D ligands and HSP70. Taken together, these data indicate that HDAC inhibition results in the elimination of the tumor cell's “invisibility cloak” that prevents T cells from recognizing and killing them. Finally, as checkpoint blockade therapy moves into the adjuvant setting, its combined use with locally administrated HDACi represents a new approach to be included in our current therapeutic treatment toolbox.

DNT Cell-based Immunotherapy: Progress and Applications

Cancer immunotherapy has firmly established a dominant status in recent years. Adoptive cellular immunotherapy (ACI) is the main branch of immunotherapy. Recently, the immune effector cells of ACI, such as T cells, NK cells, and genetically engineered cells, have been used to achieve significant clinical benefits in the treatment of malignant tumors. However, the clinical applications have limitations, including toxicity, unexpectedly low efficiency, high costs and strict technical requirements. More exploration is needed to optimize ACI for cancer patients. CD3+CD4-CD8- double negative T cells (DNTs) have emerged as functional antitumor effector cells, according to the definition of adoptive immunotherapy. They constitute a kind of T cell subset that mediates nontumor antigen-restricted immunity and has important immune regulatory functions. Preclinical experiments showed that DNTs had a dual effect by killing tumor cells and inhibiting graft-versus-host disease. Notably, DNTs can be acquired from healthy donors and expanded in vitro; thus, allogeneic DNTs may be provided as “off-the-shelf” cellular products that can be readily available for direct clinical application. We review the progress and application of DNTs in immunotherapy. DNTs may provide some novel perspectives on cancer immunotherapy.

PEPITEM/Cadherin 15 Axis Inhibits T Lymphocyte Infiltration and Glomerulonephritis in a Mouse Model of Systemic Lupus Erythematosus

Control of lymphocyte infiltration in kidney is a potential therapeutic strategy for lupus nephritis, considering that control of lymphocyte migration by sphingosine 1 phosphate has been implicated in inflammation-related pathology. The peptide inhibitor of the transendothelial migration (PEPITEM)/cadherin (CDH) 15 axis was recently reported to promote sphingosine 1 phosphate secretion. In this study, we investigated whether CDH15 is expressed in the kidney of MRL/lpr mice and whether lymphocyte infiltration is suppressed by exogenously administered PEPITEM. Mice (18 wk old) were randomized into 4-wk treatment groups that received PEPITEM or PBS encapsulated in dipalmitoylphosphatidylcholine liposomes. Enlargement of the kidney, spleen, and axillary lymph nodes was suppressed by PEPITEM treatment, which also blocked infiltration of double-negative T lymphocytes into the kidney and glomerular IgG/C3 deposition, reduced proteinuria, and increased podocyte density. Immunohistochemical analysis revealed that the PEPITEM receptor CDH15 was expressed on vascular endothelial cells of glomeruli and kidney arterioles, skin, and peritoneum in lupus mice at 22 wk of age but not in 4-wk-old mice. These results suggest that PEPITEM inhibits lymphocyte migration and infiltration into the kidney, thereby preserving the kidney structure and reducing proteinuria. Thus, PEPITEM administration may be considered as a potential therapeutic tool for systemic lupus erythematosus.

High-Frequency Irreversible Electroporation for Treatment of Primary Liver Cancer: A Proof-of-Principle Study in Canine Hepatocellular Carcinoma

PURPOSE

To determine the safety and feasibility of percutaneous high-frequency irreversible electroporation (HFIRE) for primary liver cancer and evaluate the HFIRE-induced local immune response.

MATERIALS AND METHODS

HFIRE therapy was delivered percutaneously in 3 canine patients with resectable hepatocellular carcinoma (HCC) in the absence of intraoperative paralytic agents or cardiac synchronization. Pre- and post-HFIRE biopsy samples were processed with histopathology and immunohistochemistry for CD3, CD4, CD8, and CD79a. Blood was collected on days 0, 2, and 4 for complete blood count and chemistry. Numeric models were developed to determine the treatment-specific lethal thresholds for malignant canine liver tissue and healthy porcine liver tissue.

RESULTS

HFIRE resulted in predictable ablation volumes as assessed by posttreatment CT. No detectable cardiac interference and minimal muscle contraction occurred during HFIRE. No clinically significant adverse events occurred secondary to HFIRE. Microscopically, a well-defined ablation zone surrounded by a reactive zone was evident in the majority of samples. This zone was composed primarily of maturing collagen interspersed with CD3+/CD4-/CD8- lymphocytes in a proinflammatory microenvironment. The average ablation volumes for the canine HCC patients and the healthy porcine tissue were 3.89 cm3 ± 0.74 and 1.56 cm3 ± 0.16, respectively (P = .03), and the respective average lethal thresholds were 710 V/cm ± 28.2 and 957 V/cm ± 24.4 V/cm (P = .0004).

CONCLUSIONS

HFIRE can safely and effectively be delivered percutaneously, results in a predictable ablation volume, and is associated with lymphocytic tumor infiltration. This is the first step toward the use of HFIRE for treatment of unresectable liver tumors.

TBET-expressing Th1 CD4+ T cells accumulate in chronic lymphocytic leukaemia without affecting disease progression in Eµ-TCL1 mice

Chronic lymphocytic leukaemia (CLL) is associated with alterations in T cell number, subset distribution and function. Among these changes, an increase in CD4⁺ T cells was reported. CD4⁺ T cells are a heterogeneous population and distinct subsets have been described to exert pro- and anti-tumour functions. In CLL, controversial reports describing the dominance of IFNγ-expressing Th1 T cells or of IL-4-producing Th2 T cells exist. Our study shows that blood of CLL patients is enriched in Th1 T cells producing high amounts of IFNγ. Moreover, we observed that their frequency remains relatively stable in CLL patients over a time course of five years. Furthermore, we provide evidence for an accumulation of Th1 T cells in the Eµ-TCL1 mouse model of CLL. As TBET (encoded by Tbx21) is a crucial transcription factor for Th1 polarization, we generated Tbx21^-/- bone marrow chimaeric mice which showed a lower number of IFNγ-producing Th1 T cells, and used them for adoptive transfer of Eµ-TCL1 leukaemia. Disease development in these mice was, however, comparable to that in wild-type controls, excluding a major role for TBET-expressing Th1 cells in Eµ-TCL1 leukaemia. Collectively, our data highlight that Th1 T cells accumulate in CLL but reducing their number has no impact on disease development.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Pregnancy and lactation interfere with the response of autoimmunity to modulation of gut microbiota

BACKGROUND

Dysbiosis of gut microbiota exists in the pathogenesis of many autoimmune diseases, including systemic lupus erythematosus (lupus). Lupus patients who experienced pregnancy usually had more severe disease flares post-delivery. However, the possible role of gut microbiota in the link between pregnancy and exacerbation of lupus remains to be explored.

RESULTS

In the classical lupus mouse model MRL/lpr, we compared the structures of gut microbiota in pregnant and lactating individuals vs. age-matched naïve mice. Consistent with studies on non-lupus mice, both pregnancy and lactation significantly changed the composition and diversity of gut microbiota. Strikingly, modulation of gut microbiota using the same strategy resulted in different disease outcomes in postpartum (abbreviated as "PP," meaning that the mice had undergone pregnancy and lactation) vs. control (naïve; i.e., without pregnancy or lactation) MRL/lpr females; while vancomycin treatment attenuated lupus in naïve mice, it did not do so, or even exacerbated lupus, in PP mice. Lactobacillus animalis flourished in the gut upon vancomycin treatment, and direct administration of L. animalis via oral gavage recapitulated the differential effects of vancomycin in PP vs. control mice. An enzyme called indoleamine 2,3-dioxygenase was significantly inhibited by L. animalis; however, this inhibition was only apparent in PP mice, which explained, at least partially, the lack of beneficial response to vancomycin in these mice. The differential production of immunosuppressive IL-10 and proinflammatory IFNγ in PP vs. control mice further explained why the disease phenotypes varied between the two types of mice bearing the same gut microbiota remodeling strategy.

CONCLUSIONS

These results suggest that pregnancy and lactation interfere with the response of autoimmunity to modulation of gut microbiota. Further studies are necessary to better understand the complex relationship between pregnancy and lupus.

Sh3bp2 Gain-Of-Function Mutation Ameliorates Lupus Phenotypes in B6.MRL-Faslpr Mice

SH3 domain-binding protein 2 (SH3BP2) is an adaptor protein that is predominantly expressed in immune cells, and it regulates intracellular signaling. We had previously reported that a gain-of-function mutation in SH3BP2 exacerbates inflammation and bone loss in murine arthritis models. Here, we explored the involvement of SH3BP2 in a lupus model. Sh3bp2 gain-of-function (P416R knock-in; Sh3bp2^KI/+) mice and lupus-prone B6.MRL-Fas^lpr mice were crossed to yield double-mutant (Sh3bp2^KI/+Fas^lpr/lpr) mice. We monitored survival rates and proteinuria up to 48 weeks of age and assessed renal damage and serum anti-double-stranded DNA antibody levels. Additionally, we analyzed B and T cell subsets in lymphoid tissues by flow cytometry and determined the expression of apoptosis-related molecules in lymph nodes. Sh3bp2 gain-of-function mutation alleviated the poor survival rate, proteinuria, and glomerulosclerosis and significantly reduced serum anti-dsDNA antibody levels in Sh3bp2^KI/+Fas^lpr/lpr mice. Additionally, B220⁺CD4⁻CD8⁻ T cell population in lymph nodes was decreased in Sh3bp2^KI/+Fas^lpr/lpr mice, which is possibly associated with the observed increase in cleaved caspase-3 and tumor necrosis factor levels. Sh3bp2 gain-of-function mutation ameliorated clinical and immunological phenotypes in lupus-prone mice. Our findings offer better insight into the unique immunopathological roles of SH3BP2 in autoimmune diseases.

Programmed Cell Death in Immune Defense: Knowledge and Presumptions

Cell-culture studies are our main source of knowledge of the various forms of programmed cell death. Yet genetic perturbations of death-protein function in animal models are almost the only source of our knowledge of the physiological roles of these programs. Shortcomings in the state of knowledge acquired by these two experimental approaches are exemplified in this Perspective by reference to research on the contribution of apoptosis to lymphocyte development, a subject on which there is already much knowledge, and on the role of necroptosis in inflammation, about which information is just beginning to emerge. To address these shortcomings, there is need to find ways to verify the notions obtained through the current experimental approaches by directly monitoring death programs within specific cells in vivo.

Comprehensive Phenotyping of T Cells Using Flow Cytometry

The T cell compartment can form a powerful defense against extrinsic (e.g., pathogens) and intrinsic danger (e.g., malignant cells). At the same time, specific subsets of T cells control this process to keep the immune system in check and prevent autoimmunity. A wide variety in T cell functionalities exists, which is dependent on the differentiation and maturation state of the T cells. In this review, we report an overview for the identification of CD4⁺ T-αβ cells (T-helper (Th)1, Th2, Th9, Th17, Th22, and CD4⁺ regulatory T cells), CD8⁺ T-αβ cells (cytotoxic T lymphocyte (Tc)1, Tc2, Tc9, Tc17, and CD8⁺ regulatory T cells), and their additional effector memory status (naïve, stem cell memory, central memory, effector memory, and effector) using flow cytometry. These different subsets can be discriminated based on selective extracellular markers, in combination with intracellular transcription factor and/or cytokine stainings. Additionally, identification of very small subsets, including antigen-specific T cells, and important technical considerations of flow cytometry are discussed. Together, this overview can be used for comprehensive phenotyping of a T cell subset of interest. © 2019 International Society for Advancement of Cytometry.

Tetra-arsenic tetra-sulfide ameliorates lupus syndromes by inhibiting IL-17 producing double negative T cells

Systemic lupus erythematosus (SLE) is an autoimmune disease of uncertain etiology that affects multiple tissues and organs. Tetra-arsenic tetra-sulfide (As₄ S₄ ), a traditional Chinese medicine, is effective on acute promyelocytic leukemia with mild side effects. In our previous study, BXSB lupus-prone mice treated with As₄ S₄ has showed improved monocytosis, decreased serum interleukin (IL)-6 and suppressed skin, liver and renal lesions with well-tolerance. In this study, we explored the effect and mechanism of As₄ S₄ on the MRL/lpr mice. MRL/lpr and wild MRL/MpJ mice were divided into control and As₄ S₄ treatment groups and dosed with As₄ S₄ or placebo for 8 weeks. We found that As₄ S₄ prevented the skin, renal and lung lesions of MRL/lpr mice. As₄ S₄ significantly decreased the double negative T (DN T) cells and reduced the serum levels of IL-17, IL-10, and antinuclear antibodies titer. Further results revealed that the FasL was decreased, and activated caspases elevated in DN T cells in As₄ S₄ treated MRL/lpr mice. Taken together, As₄ S₄ could selectively suppresses DN T cells by inducing apoptosis. It also reduced inflammatory cytokines IL-17, which may be produced by DN T cells. As₄ S₄ may represent a new therapy for SLE.

CD8+, but not CD4+ effector/memory T cells, express the CD44highCD45RBhigh phenotype with aging, which displays reduced expression levels of P2X7 receptor and ATP-induced cellular responses

Previously we reported that the sensitivity of CD4⁺ T cells to ATP does not depend on P2X₇ receptor (P2X₇R) expression levels but on their activation and differentiation stages. Therefore, here we have investigated a potential relationship between the sensitivity of CD8⁺ T cells to ATP and their stages of differentiation. Thus, the CD8⁺ subpopulation exhibits a drastically reduced sensitivity to ATP with aging, which parallels the strong increase of an effector/memory CD8⁺ subset expressing high levels of CD44 cell adhesion molecule and CD45RB transmembrane phosphatase (CD44^hiCD45RB^hi). Using l-selectin/CD62L, CC-chemokine receptor 7, and CD127/IL-7 receptor-α markers, we showed that effector/memory CD8⁺ T cells belong to a central or effector memory subset. In contrast, the CD44^hiCD45RB^hi effector/memory subset is absent or poorly expressed in the CD4⁺ T subpopulation regardless of age. While ATP treatment can trigger channel and pore formation, CD62L shedding, phosphatidylserine exposure, and cell death in the CD44^loCD45RB^hi-naive CD8⁺ subset, it is unable to induce these cellular activities in the CD44^hiCD45RB^hi effector/memory CD8⁺ subset. Importantly, both CD44^loCD45RB^hi-naive and CD44^hiCD45RB^hi effector/memory subsets express similar low levels of P2X₇R, demonstrating that the sensitivity of CD8⁺ T cells to ATP depends on the stage of differentiation instead of P2X₇R expression levels.-Mellouk, A., Bobé, P. CD8⁺, but not CD4⁺ effector/memory T cells, express the CD44^highCD45RB^high phenotype with aging, which displays reduced expression levels of P2X₇ receptor and ATP-induced cellular responses.

mTOR inhibitor INK128 attenuates systemic lupus erythematosus by regulating inflammation-induced CD11b+Gr1+ cells

Systemic lupus erythematosus (SLE) is an autoimmune disease, characterized by systemic chronic inflammation that can affect multiple major organ systems. Although the etiology of SLE is known to involve a variety of factors such as the environment, random factors and genetic susceptibility, the exact role of CD11b⁺Gr1⁺ myeloid cells in lupus progression is not fully understood. Myeloid-derived CD11b⁺Gr1⁺ cells are thought to be a heterogeneous group of immature myeloid cells with immune function. Some studies have reported that CD11b⁺Gr1⁺ cells and the activation of mTOR pathway are involved in the pathogenesis of systemic lupus erythematosus (SLE). However, it is still not clarified about the mechanism of influence of lupus microenvironment and mTOR signaling on CD11b⁺Gr1⁺ cells. In the present study, we found that the percentage of CD11b⁺Gr1⁺ cells increased prior to the abnormal changes of Th17, Treg, T and B cells during lupus development. TLR7 and IFN-α signaling synergized to promote CD11b⁺Gr1⁺ cell accumulation in an mTOR-dependent manner. Moreover, compared to a traditional mTOR inhibitor, INK128 inhibited more effectively the disease activity via regulating CD11b⁺Gr1⁺ cell expansion and functions. Furthermore, TLR7/IFN-α-modified CD11b⁺Gr1⁺ cells promoted unbalance of Th17/Tregs and were inclined to differentiate into macrophages via the mTOR pathway. In conclusion, CD11b⁺Gr1⁺ cells increased in the early stages of the lupus progression and mTOR pathway was critical for CD11b⁺Gr1⁺ cells in lupus development, suggesting the changes of inflammation-induced CD11b⁺Gr1⁺ cells initate lupus development. We also provide evidence for the first time that INK128, a second generation mTOR inhibitor, has a good therapeutic action on lupus development by regulating CD11b⁺Gr1⁺ cells.

Tc17/IL-17A Up-Regulated the Expression of MMP-9 via NF-κB Pathway in Nasal Epithelial Cells of Patients With Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is a common chronic inflammatory disease of the upper airways involving nasal cavity and sinus. Deriving both from its clinical complexity with protean clinical manifestations as well its pathogenetic heterogeneity, the molecular mechanisms contributing to the pathogenesis of CRS remain unclear, and attract a wide interest in the field. Current evidences indicate that IL-17A is highly expressed in chronic rhinosinusitis with nasal polyps (CRSwNP). However, its pathogenetic role in regulation of tissue remodeling of CRSwNP remains unknown. The present study aimed to investigate the cellular origins and functions of IL-17A cytokine in CRSwNP, and further determined whether IL-17A could affect the expression of metalloproteinases (MMPs), the remodeling factors of CRSwNP. The results showed that the expression of IL-17A was upregulated in nasal tissues of patients with CRSwNP compared to those with chronic rhinosinusitis without nasal polyps (CRSsNP) and controls. CD8⁺ cytotoxic T lymphocytes (Tc) were major IL-17A producers in nasal tissues of CRSwNP. Interleukin (IL)-17-producing CD8⁺ T cells (Tc17) was significantly higher in nasal tissues of CRSwNP than CRSsNP and controls. Nonetheless, no difference was observed among the IL-17A in peripheral blood lymphocytes of these three groups. Moreover, in the same patients, IL-17A expression was negligible in lymphocytes of peripheral blood when compared with nasal tissues. Increased gene and protein expression of MMP-7 and MMP-9 in patients with CRSwNP compared with controls were observed. In CRSwNP samples, IL-17A receptor (IL-17AR) co-localized with MMP-9 and they were mainly expressed in the epithelial cells. MMP-9 expression was up-regulated both in Primary human nasal epithelial cells (PHNECs) and a nasal epithelial cell line (RPMI 2650) by IL-17A treatment, and diminished by anti-IL-17AR treatment. Furthermore, IL-17A promoted the expression of MMP-9 by activating the NF-κB signal pathway. Thus, our results have revealed a crucial role of IL-17A and Tc cells on pathogenesis and tissue remodeling of CRSwNP.

IL-17 and limits of success

Interleukin-17 (IL-17) is a potent proinflammatory cytokine that protects a host against fungal and extracellular bacterial infections. On the other hand, excessive or dysregulated production of IL-17 underlines susceptibility to autoimmune disease. Consequently, blocking IL-17 has become an effective strategy for modulating several autoimmune diseases, including multiple sclerosis (MS), psoriasis, and rheumatoid arthritis (RA). Notably, however, IL-17 blockade remains ineffective or even pathogenic against important autoimmune diseases such as inflammatory bowel disease (IBD). Furthermore, the efficacy of IL-17 blockade against other autoimmune diseases, including type 1 diabetes (T1D) is currently unknown and waiting results of ongoing clinical trials. Coming years will determine whether the efficacy of IL-17 blockade is limited to certain autoimmune diseases or can be expanded to other autoimmune diseases. These efforts include new clinical trials aimed at testing second-generation agents with the goal of increasing the efficiency, spectrum, and ameliorating side effects of IL-17 blockade. Here we briefly review the roles of IL-17 in the pathogenesis of selected autoimmune diseases and provide updates on ongoing and recently completed trials of IL-17 based immunotherapies.

TCRαβ+CD3+CD4-CD8- (double negative) T cells in autoimmunity

TCRαβ⁺CD3⁺CD4^-CD8^- "double negative" (DN) T cells comprise a small subset of mature peripheral T cells. The origin and function of DN T cells are somewhat unclear and discussed controversially. While DN T cells resemble a rare and heterogeneous T cell subpopulation in healthy individuals, numbers of TCRαβ⁺ DN T cells are expanded in several inflammatory conditions, where they also exhibit distinct effector phenotypes and infiltrate inflamed tissues. Thus, DN T cells may be involved in systemic inflammation and tissue damage in autoimmune/inflammatory conditions, including SLE, Sjögren's syndrome, and psoriasis. Here, the current understanding of the origin and phenotype of DN T cells, and their role in the instruction of immune responses, autoimmunity and inflammation will be discussed in health and disease.

Prenatal Administration of Betamethasone Causes Changes in the T Cell Receptor Repertoire Influencing Development of Autoimmunity

Prenatal glucocorticoids are routinely administered to pregnant women at risk of preterm delivery in order to improve survival of the newborn. However, in half of the cases, birth occurs outside the beneficial period for lung development. Glucocorticoids are potent immune modulators and cause apoptotic death of immature T cells, and we have previously shown that prenatal betamethasone treatment at doses eliciting lung maturation induce profound thymocyte apoptosis in the offspring. Here, we asked if there are long-term consequences on the offspring’s immunity after this treatment. In the non-obese diabetic mouse model, prenatal betamethasone clearly decreased the frequency of pathogenic T cells and the incidence of type 1 diabetes (T1D). In contrast, in the lupus-prone MRL/lpr strain, prenatal glucocorticoids induced changes in the T cell repertoire that resulted in more autoreactive cells. Even though glucocorticoids transiently enhanced regulatory T cell (Treg) development, these cells did not have a protective effect in a model for multiple sclerosis which relies on a limited repertoire of pathogenic T cells for disease induction that were not affected by prenatal betamethasone. We conclude that prenatal steroid treatment, by inducing changes in the T cell receptor repertoire, has unforeseeable consequences on development of autoimmune disease. Our data should encourage further research to fully understand the consequences of this widely used treatment.

Autoimmune lymphoproliferative syndrome: more than a FAScinating disease

Autoimmune lymphoproliferative syndrome (ALPS) is an inherited syndrome characterized by abnormal lymphocyte survival caused by failure of apoptotic mechanisms to maintain lymphocyte homeostasis. This failure leads to the clinical manifestations of non-infectious and non-malignant lymphadenopathy, splenomegaly, and autoimmune pathology, most commonly, autoimmune cytopenias. Since ALPS was first characterized in the early 1990s, insights in disease biology have improved both diagnosis and management of this syndrome. Sirolimus is the best-studied and most effective corticosteroid-sparing therapy for ALPS and should be considered first-line for patients in need of chronic treatment. This review highlights practical clinical considerations for the diagnosis and management of ALPS. Further studies could reveal new proteins and regulatory pathways that are critical for lymphocyte activation and apoptosis.

Circulating T-Cell Subsets, Monocytes, and Natural Killer Cells in Peripartum Cardiomyopathy: Results From the Multicenter IPAC Study

OBJECTIVE

The aim of this work was to evaluate the hypothesis that the distribution of circulating immune cell subsets, or their activation state, is significantly different between peripartum cardiomyopathy (PPCM) and healthy postpartum (HP) women.

BACKGROUND

PPCM is a major cause of maternal morbidity and mortality, and an immune-mediated etiology has been hypothesized. Cellular immunity, altered in pregnancy and the peripartum period, has been proposed to play a role in PPCM pathogenesis.

METHODS

The Investigation of Pregnancy-Associated Cardiomyopathy (IPAC) study enrolled 100 women presenting with a left ventricular ejection fraction of <0.45 within 2 months of delivery. Peripheral T-cell subsets, natural killer (NK) cells, and cellular activation markers were assessed by flow cytometry in PPCM women early (<6 wk), 2 months, and 6 months postpartum and compared with those of HP women and women with non-pregnancy-associated recent-onset cardiomyopathy (ROCM).

RESULTS

Entry NK cell levels (CD3-CD56+CD16+; reported as % of CD3- cells) were significantly (P < .0003) reduced in PPCM (6.6 ± 4.9% of CD3- cells) compared to HP (11.9 ± 5%). Of T-cell subtypes, CD3+CD4-CD8-CD38+ cells differed significantly (P < .004) between PPCM (24.5 ± 12.5% of CD3+CD4-CD8- cells) and HP (12.5 ± 6.4%). PPCM patients demonstrated a rapid recovery of NK and CD3+CD4-CD8-CD38+ cell levels. However, black women had a delayed recovery of NK cells. A similar reduction of NK cells was observed in women with ROCM.

CONCLUSIONS

Compared with HP control women, early postpartum PPCM women show significantly reduced NK cells, and higher CD3+CD4-CD8-CD38+ cells, which both normalize over time postpartum. The mechanistic role of NK cells and "double negative" (CD4-CD8-) T regulatory cells in PPCM requires further investigation.

Bortezomib treatment induces a higher mortality rate in lupus model mice with a higher disease activity

Background

Bortezomib (Bz) is a proteasome inhibitor that directly targets antibody-producing plasma cells. We recently reported the first randomized control trial that evaluated the effects of Bz in patients with systemic lupus erythematosus (SLE). In that study, we demonstrated that Bz treatment is associated with many adverse reactions in patients with refractory disease. In the present study, we examine the therapeutic and toxic effects of Bz on MRL/MpJ-lpr/lpr (MRL/lpr) mice with severe disease activity.

Methods

Female MRL/lpr mice at 10 and 14 weeks of age were treated with phosphate buffered saline (PBS) (n = 19), Bz (750 μg/kg twice weekly) (n = 27), or cyclophosphamide (Cyc) (1 mg/body, once in 2 weeks) (n = 20). Cellular subsets, serum immunoglobulin, anti-double-stranded DNA (anti-dsDNA) antibody titer, and a pathological index of glomerulonephritis were then analyzed at 22 weeks of age. Survival curves of the 10-week-old and 14-week-old Bz-treated groups were compared. Blood counts, creatinine, liver enzymes, and serum cytokine levels were measured 1 week after Bz treatment. Gene expression profiling of spleens from Bz and Cyc treatment mice were compared with those from control mice.

Results

The anti-dsDNA antibody levels were significantly higher in 14-week-old than in 10-week-old mice, indicating a higher disease activity at 14 weeks. A significant decrease in the number of splenic cells and glomerulonephritis index was observed in Bz-treated and Cyc-treated mice. Bz, but not Cyc, significantly decreased serum immunoglobulin and anti-dsDNA antibody titer levels. Survival curve analysis revealed a significantly higher mortality rate in 14-week-old than in 10-week-old Bz-treated and control groups. Following two injections of Bz, serum IL-6 and TNF-α levels were significantly more elevated in 14-week-old than in 10-week-old mice. Potentially immunogenic molecules, such as heat shock proteins, were characteristically upregulated in spleens of Bz-treated but not Cyc-treated mice.

Conclusions

In spite of its therapeutic effect, Bz treatment had more toxic effects associated with increased proinflammatory cytokine levels in mice with a higher disease activity. Understanding the mechanism of the toxicity and developing preventive strategies against it is important for the safe clinical application of Bz in human SLE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1397-7) contains supplementary material, which is available to authorized users.

Assessing Autophagy in Mouse Models and Patients with Systemic Autoimmune Diseases

Autophagy is a tightly regulated mechanism that allows cells to renew themselves through the lysosomal degradation of proteins, which are misfolded or produced in excess, and of damaged organelles. In the context of immunity, recent research has specially attempted to clarify its roles in infection, inflammation and autoimmunity. Autophagy has emerged as a spotlight in several molecular pathways and trafficking events that participate to innate and adaptive immunity. Deregulation of autophagy has been associated to several autoimmune diseases, in particular to systemic lupus erythematosus. Nowadays, however, experimental data on the implication of autophagy in animal models of autoimmunity or patients remain limited. In our investigations, we use Murphy Roths Large (MRL)/lymphoproliferation (lpr) lupus-prone mice as a mouse model for lupus and secondary Sjögren's syndrome, and, herein, we describe methods applied routinely to analyze different autophagic pathways in different lymphoid organs and tissues (spleen, lymph nodes, salivary glands). We also depict some techniques used to analyze autophagy in lupus patient's blood samples. These methods can be adapted to the analysis of autophagy in other mouse models of autoinflammatory diseases. The understanding of autophagy implication in autoimmune diseases could prove to be very useful for developing novel immunomodulatory strategies. Our attention should be focused on the fact that autophagy processes are interconnected and that distinct pathways can be independently hyper-activated or downregulated in distinct organs and tissues of the same individual.