Protein kinase cδ deficiency causes mendelian systemic lupus erythematosus with B cell-defective apoptosis and hyperproliferation

OBJECTIVE

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease that is assumed to occur via a complex interplay of environmental and genetic factors. Rare causes of monogenic SLE have been described, providing unique insights into fundamental mechanisms of immune tolerance. The aim of this study was to identify the cause of an autosomal-recessive form of SLE.

METHODS

We studied 3 siblings with juvenile-onset SLE from 1 consanguineous kindred and used next-generation sequencing to identify mutations in the disease-associated gene. We performed extensive biochemical, immunologic, and functional assays to assess the impact of the identified mutations on B cell biology.

RESULTS

We identified a homozygous missense mutation in PRKCD, encoding protein kinase δ (PKCδ), in all 3 affected siblings. Mutation of PRKCD resulted in reduced expression and activity of the encoded protein PKCδ (involved in the deletion of autoreactive B cells), leading to resistance to B cell receptor- and calcium-dependent apoptosis and increased B cell proliferation. Thus, as for mice deficient in PKCδ, which exhibit an SLE phenotype and B cell expansion, we observed an increased number of immature B cells in the affected family members and a developmental shift toward naive B cells with an immature phenotype.

CONCLUSION

Our findings indicate that PKCδ is crucial in regulating B cell tolerance and preventing self-reactivity in humans, and that PKCδ deficiency represents a novel genetic defect of apoptosis leading to SLE.

CD4+CD25+CD127- assessment as a surrogate phenotype for FOXP3+ regulatory T cells in HIV-1 infected viremic and aviremic subjects

BACKGROUND

Although likely pivotal, the role of regulatory T cells (Tregs) in HIV pathogenesis remains elusive. This can be partly explained by analytical issues regarding their phenotypic identification in clinical studies. Instead of intracellular FOXP3 staining, CD4+CD25+CD127- phenotype has been proposed as an alternative to identify Tregs in clinical samples. However, its use remains controversial in viremic patients. Therefore, the objective of the present study was to assess the correlation between frequencies of CD4+CD25+CD127- and CD4+CD25+FOXP3+ lymphocytes in viremic and matched aviremic HIV-infected patients.

METHODS

Peripheral blood was collected from HIV-1 infected patients. Eleven viremic patients (Viral Load > 40 copies/mL) were matched (age, sex, CD4+ cell number) with 8 aviremic patients under highly active antiretroviral therapy (HAART). Fresh whole blood was immediately stained to analyze by flow cytometry the correlation between CD4+CD25+CD127- and the reference phenotype CD4+CD25+FOXP3+ lymphocytes in the same tube (four color staining CD4/CD25/CD127/FOXP3 for concomitant analysis of cell surface and intracellular markers).

RESULTS

In both groups, no significant differences were observed when comparing CD4+CD25+CD127- and CD4+CD25+FOXP3+ cell frequencies. In line, a strong correlation between CD4+CD25+CD127- and CD4+CD25+FOXP3+ lymphocyte percentages was observed in the whole patient population (r: 0.948, P < 0.001) or each group separately: aviremic (r: 0.968, P < 0.001), viremic (r: 0.9, P < 0.001). Finally, we found that most CD4+FOXP3+ cells were indeed CD25+CD127-, both in viremic and aviremic groups (88.5% and 90.9%, respectively).

CONCLUSIONS

We observed that CD4+CD25+CD127- phenotype is a good and easy-to-perform surrogate identification strategy for FOXP3+ regulatory T cells in both viremic and aviremic HIV-1-infected subjects. Thus, it represents a useful tool for monitoring Tregs in clinical research studies based on large cohorts of patients prospectively monitored, including HIV-infected subjects.

Programmed death-1 levels correlate with increased mortality, nosocomial infection and immune dysfunctions in septic shock patients

INTRODUCTION

Septic shock remains a major health care problem worldwide. Sepsis-induced immune alterations are thought to play a major role in patients' mortality and susceptibility to nosocomial infections. Programmed death-1 (PD-1) receptor system constitutes a newly described immunoregulatory pathway that negatively controls immune responses. It has recently been shown that PD-1 knock-out mice exhibited a lower mortality in response to experimental sepsis. The objective of the present study was to investigate PD-1-related molecule expressions in septic shock patients.

METHODS

This prospective and observational study included 64 septic shock patients, 13 trauma patients and 49 healthy individuals. PD-1-related-molecule expressions were measured by flow cytometry on circulating leukocytes. Plasmatic interleukin (IL)-10 concentration as well as ex vivo mitogen-induced lymphocyte proliferation were assessed.

RESULTS

We observed that septic shock patients displayed increased PD-1, PD-Ligand1 (PD-L1) and PD-L2 monocyte expressions and enhanced PD-1 and PD-L1 CD4+ T lymphocyte expressions at day 1-2 and 3-5 after the onset of shock in comparison with patients with trauma and healthy volunteers. Importantly, increased expressions were associated with increased occurrence of secondary nosocomial infections and mortality after septic shock as well as with decreased mitogen-induced lymphocyte proliferation and increased circulating IL-10 concentration.

CONCLUSIONS

These findings indicate that PD-1-related molecules may constitute a novel immunoregulatory system involved in sepsis-induced immune alterations. Results should be confirmed in a larger cohort of patients. This may offer innovative therapeutic perspectives on the treatment of this hitherto deadly disease.

Proatrial natriuretic peptide is a better predictor of 28-day mortality in septic shock patients than proendothelin-1

BACKGROUND

Septic shock is a major health care problem that affects a heterogeneous population of patients. To improve sepsis management, a key point is to decrease this heterogeneity by stratifying patients according to specific criteria, such as appropriate biomarkers. As the early phase of septic shock is characterized by cardiovascular dysfunction, precursors of vasoactive hormones represent interesting candidates. The objective of the present study was to concomitantly assess the predictive value of C-terminal proendothelin-1 and midregional proatrial natriuretic peptide (CT-proET-1 and MR-proANP, respectively vasoconstrictor and vasodilator) on 28-day mortality following septic shock.

METHODS

In this observational study which included 99 patients, concentrations of MR-proANP and CT-proET-1 were measured using an immunoluminometric assay three times within the first week after the onset of septic shock.

RESULTS

While MR-proANP concentrations were significantly increased in non-survivors in comparison with survivors, no differences were noted for CT-proET-1. Increased MR-proANP concentrations were significantly associated with mortality after both univariate and multivariate analyses, adjusted for usual clinical confounders [SAPS II (simplified acute physiology score II), SOFA (sepsis-related organ failure assessment) scores and number of co-morbidities].

CONCLUSIONS

In septic shock patients, MR-proANP appears to be a good predictor of 28-day mortality, whereas CT-proET-1 does not present any predictive value during monitoring.

Preferential increase in memory and regulatory subsets during T-lymphocyte immune reconstitution after Thymoglobulin induction therapy with maintenance sirolimus vs cyclosporine

BACKGROUND

Sirolimus maintenance therapy with Thymoglobulin induction is a promising regimen that may preserve renal function. Data are lacking, however, about the immunologic effects of combined Thymoglobulin-sirolimus.

METHODS

In a 12-month, prospective, randomised, open-label, single-centre pilot study, de novo deceased-donor kidney transplant patients were randomised to receive cyclosporine or sirolimus, with Thymoglobulin induction, mycophenolate mofetil and corticosteroids. Flow cytometry analysis of peripheral blood was used to evaluate immune reconstitution.

RESULTS

Nineteen patients were recruited (sirolimus 9, cyclosporine 10). Reconstitution of the CD4(+) T-lymphocyte subset was significantly lower with sirolimus versus cyclosporine over year 1, but CD8(+) reconstitution did not differ significantly between groups. The proportion of naïve CD4(+) T-lymphocytes showed an initial decrease with sirolimus versus cyclosporine. Naïve CD8(+) T-lymphocytes increased versus baseline in the cyclosporine cohort at months 1 and 3, but remained unchanged with sirolimus. Memory CD4(+) T-lymphocytes occurred more frequently in sirolimus- versus cyclosporine-treated patients during year 1. The proportion of memory CD8(+) T-lymphocytes decreased at months 1 and 3 compared to baseline in the CsA arm, but did not change in the sirolimus cohort. By month 12, the proportion of both naïve and memory CD4(+) and CD8(+) T-lymphocytes had become similar with sirolimus or cyclosporine. There were fewer naïve B-lymphocytes in the sirolimus cohort and more CD19(-)IgD(+/-)CD27(+) memory B-lymphocytes.

CONCLUSIONS

In this small population, homeostatic reconstitution after Thymoglobulin induction showed disproportionately high recovery of memory T-lymphocyte subsets during sirolimus therapy, which may explain the higher rejection rate seen with sirolimus versus cyclosporine following kidney transplantation.

Human mesenchymal stem cells and immunosuppressive drug interactions in allogeneic responses: an in vitro study using human cells

OBJECTIVES

The use of mesenchymal stem cells (MSC), which display immunosuppressive activity, seems to be a promising therapeutic approach in solid organ transplantation. However, little is known about their interactions with immunosuppressive drugs. The objective of this study was to assess these interactions in allogeneic responses.

METHODS

We studied the effects on alloimmune responses in mixed lymphocyte reactions of MSC plus five agents-cyclosporine, tacrolimus, rapamycin, mycophenolate acid (MPA), and dexamethasone (DEX).

RESULTS

Human MSC isolated from bone marrow were characterized by their phenotype and their ability to differentiate into adipocytes or osteoblastes. MSC plus the agents inhibited allogeneic lymphocyte proliferation in a dose-dependent manner. Calcineurin inhibitors and rapamycin antagonized the inhibitory effect of MSC, whereas MPA promoted it and DXM did not modify it.

CONCLUSION

MPA seems to be the best immunosuppressant to associated with MSC for transplanted patients.

Percentage of regulatory T cells CD4+CD25+CD127- in HIV-infected patients is not reduced after cryopreservation

Interest in regulatory T cells (Treg) has been continuously growing over the last 10years. In particular, a role for Treg has been recently reported in HIV. It is crucial to investigate their conservation over time, once sampled and purified. The objective of the present study was to investigate whether cryopreservation may modify recognition and measurement of relative frequency of Treg (CD4(+)CD25(+)CD127(-)) among PBMCs purified from 17 HIV-infected patients. Ours results indicate that cryopreservation does not affect this specific T lymphocyte subset.

Assessment of pro-vasopressin and pro-adrenomedullin as predictors of 28-day mortality in septic shock patients

PURPOSE

Improvements in survival after septic shock will most likely rely on our capacity to manage individualized therapies based on the measurement of rapidly accessible biomarkers. As the early phase of septic shock is dominated by severe alterations of the cardiovascular system, the predictive value for mortality of pro-vasopressin (pro-AVP) and pro-adrenomedullin (pro-ADM), two vasoactive pro-hormones, was assessed.

METHODS

In 99 consecutive patients, pro-hormone concentrations were measured (immunoluminometric assay) three times within the first week after the onset of septic shock.

RESULTS

Pro-AVP and pro-ADM concentrations were significantly increased in non-survivors in comparison with survivors and were significantly associated with mortality after both univariate and multivariate analysis. Importantly, when assessed as a pair, pro-ADM and pro-AVP were even more informative.

CONCLUSIONS

Both Pro-ADM and pro-AVP appear to be good biomarkers for the prediction of 28-day mortality after septic shock. However, their association in a single variable tends to improve their predictive capacity.

Neutralising antibodies to interferon β in multiple sclerosis

Interferon beta (IFNbeta) therapy for multiple sclerosis (MS) is associated with a potential for the development of neutralising antibodies (NAbs) that negatively affect therapy. Several factors influence the development of NAbs, such as lack of complete sequence homology with the endogenous IFNbeta sequence, frequency of administration, level of dose and formulation of IFNbeta. Taken together, the evidence that NAb status reduces clinical efficacy in MS patients is strong. Standardised assays for NAbs are lacking, and titres vary over time. NAb testing is a critical component of care for MS patients because it provides information on one of the most important factors determining clinical responsiveness to IFNbeta therapy. This expert panel report attempts to move the field towards resolution of the remaining issues and considers several aspects of NAbs, including their clinical relevance, factors influencing immunogenicity, assays to quantify NAbs and the definition of clinically relevant titres.

Bone marrow CD34+/B220+ progenitors target the inflamed brain and display in vitro differentiation potential toward microglia

Recent evidence indicates that microglial cells may not derive from blood circulating mature monocytes as they express features of myeloid progenitors. Here, we observed that a subpopulation of microglial cells expressed CD34 and B220 antigens during brain development. We thus hypothesized that microglia, or a subset of microglial cells, originate from blood circulating CD34+/B220+ myeloid progenitors, which could target the brain under developmental or neuroinflammatory conditions. Using experimental allergic encephalomyelitis (EAE) as a model of chronic neuroinflammation, we found that a discrete population of CD34+/B220+ cells expands in both blood and brain of diseased animals. In EAE mice, intravenous transfer experiments showed that macrophage-colony stimulating factor (M-CSF) -expanded CD34+ myeloid progenitors target the inflamed central nervous system (CNS) while keeping their immature phenotype. Based on these results, we then assessed whether CD34+/B220+ cells display in vitro differentiation potential toward microglia. For this purpose, CD34+/B220+ cells were sorted from M-CSF-stimulated bone marrow (BM) cultures and exposed to a glial cell conditioned medium. Under these experimental conditions, CD34+/B220+ cells were able to differentiate into microglial-like cells showing the morphological and phenotypic features of native microglia. Overall, our data suggest that under developmental or neuroinflammatory conditions, a subpopulation of microglial cells derive from CNS-invading CD34+/B220+ myeloid progenitors.

A role for the neuronal protein collapsin response mediator protein 2 in T lymphocyte polarization and migration

The semaphorin-signaling transducer collapsin response mediator protein 2 (CRMP2) has been identified in the nervous system where it mediates Sema3A-induced growth cone navigation. In the present study, we provide first evidence that CRMP2 is present in the immune system and plays a critical role in T lymphocyte function. CRMP2 redistribution at the uropod in polarized T cells, a structural support of lymphocyte motility, suggests that it may regulate T cell migration. This was evidenced in primary T cells by small-interfering RNA-mediated CRMP2 gene silencing and blocking Ab, as well as CRMP2 overexpression in Jurkat T cells tested in a chemokine- and semaphorin-mediated transmigration assay. Expression analysis in PBMC from healthy donors showed that CRMP2 is enhanced in cell subsets bearing the activation markers CD69+ and HLA-DR+. Heightened expression in T lymphocytes of patients suffering from neuroinflammatory disease with enhanced T cell-transmigrating activity points to a role for CRMP2 in pathogenesis. The elucidation of the signals and mechanisms that control this pathway will lead to a better understanding of T cell trafficking in physiological and pathological situations.

How to drain without lymphatics? Dendritic cells migrate from the cerebrospinal fluid to the B-cell follicles of cervical lymph nodes

The lack of draining lymphatic vessels in the central nervous system (CNS) contributes to the so-called "CNS immune privilege." However, despite such a unique anatomic feature, dendritic cells (DCs) are able to migrate from the CNS to cervical lymph nodes through a yet unknown pathway. In this report, labeled bone marrow-derived myeloid DCs were injected stereotaxically into the cerebrospinal fluid (CSF) or brain parenchyma of normal rats. We found that DCs injected within brain parenchyma migrate little from their site of injection and do not reach cervical lymph nodes. In contrast, intra-CSF-injected DCs either reach cervical lymph nodes or, for a minority of them, infiltrate the subventricular zone, where neural stem cells reside. Surprisingly, DCs that reach cervical lymph nodes preferentially target B-cell follicles rather than T-cell-rich areas. This report sheds a new light on the specific role exerted by CSF-infiltrating DCs in the control of CNS-targeted immune responses.

Déficit immunitaire commun variable avec manifestations auto-immunes : étude de neuf observations ; intérêt d’un immunophénotypage spécifique des lymphocytes B circulants chez sept patients

PURPOSE

Autoimmune manifestations (AIM) are associated to common variable immunodeficiency (CVI) in about 20 to 25% of the cases. This study presents the clinical, biological characteristics and the evolution of nine patients developing CVI and AIM. A peripheral B-cell compartment analysis has been performed in seven cases.

METHOD

This multicenter retrospective study analyses nine patients, six men and three women, within a population of 32 CVI.

RESULTS

The mean age was 27 years at the time of diagnosis of AIM and 30 years at the time of diagnosis of CVI. The diagnosis of AIM preceded the diagnosis of CVI in five cases. Thirteen AIM of different types were observed: autoimmune hemolytic anemia (AHA, 3), immune thrombocytopenic purpura (ITP, 2), Evan's syndrome (2), primary biliary cirrhosis (1), rheumatoid arthritis (1), alopecia totalis (1), myasthenia gravis (1). The peripheral B-cell compartment was investigated in seven patients: five patients with autoimmune cytopenia presented with a diminution of memory B cells (CD27+IgD-) and immature B cells (CD21-) levels; the patient with primary biliary cirrhosis and myasthenia gravis had only a diminution of memory B cells level; the last patient with ITP presented with a normal level of memory B cells. Five among the seven patients with autoimmune cytopenia required a specific treatment using corticosteroids, high dosages of intravenous immunoglobulin, then splenectomy after failure of the medical management, with severe infectious complications in one case.

CONCLUSION

The association of AIM and CVI is not fortuitous. The most common AIM is autoimmune cytopenia. The peripheral B-cell compartment analyses show that a majority of patients have a defect in memory B-cells. Treatment regimens are not standardized and splenectomy increases the risk of infectious complications.

[Astrocytes, cells involved in neuro-immune interactions in the central nervous system]

The astrocyte, the major glial cell in the central nervous system, may influence many aspects of inflammation and immune reactivity within the brain. We have established a model of chronically activated T lymphocytes, interacting with neural cells of diverse origin to study the complex immune regulatory system suspected to lead to neuroinflammatory diseases. We show that human astrocytes became reactive following T cell contact, secreting proinflammatory cytokines, matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinase (TIMP). The altered MMP/TIMP system was shown to be involved in deleterious effects displayed by activated T cells towards human multipotent neural precursers by controlling their sensitivity to T cell-induced Fas-mediated apoptosis. MMP/TIMP was suspected to stabilize Fas at the cell membrane. In a model of mixed rat glial cells in primary culture (astrocytes, oligodendrocytes), activated T lymphocytes induced the collapse of processes and the death of immature oligodendrocytes. These effects were associated with upregulation of Fas at the cell surface of oligodendrocytes and secretion of MMP and TIMP by astrocytes. By amplifying the expression of inflammatory molecules including the MMP/TIMP system, astrocytes appear to be a crucial relay in the deleterious molecular cascade triggered by activated T lymphocytes. Detection of altered MMP/TIMP in patients suffering from myelopathy associated with retroviral infection (HTLV-1) strongly suggests its involvement in the physiopathological process of the disease.

Human T-cell lymphotropic virus type 1-infected T lymphocytes impair catabolism and uptake of glutamate by astrocytes via Tax-1 and tumor necrosis factor alpha

Human T-cell lymphotropic virus type 1 (HTLV-1) is the causative agent of a chronic progressive myelopathy called tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). In this disease, lesions of the central nervous system (CNS) are associated with perivascular infiltration by lymphocytes. We and others have hypothesized that these T lymphocytes infiltrating the CNS may play a prominent role in TSP/HAM. Here, we show that transient contact of human or rat astrocytes with T lymphocytes chronically infected by HTLV-1 impairs some of the major functions of brain astrocytes. Uptake of extracellular glutamate by astrocytes was significantly decreased after transient contact with infected T cells, while the expression of the glial transporters GLAST and GLT-1 was decreased. In two-compartment cultures avoiding direct cell-to-cell contact, similar results were obtained, suggesting possible involvement of soluble factors, such as cytokines and the viral protein Tax-1. Recombinant Tax-1 and tumor necrosis factor alpha (TNF-alpha) decreased glutamate uptake by astrocytes. Tax-1 probably acts by inducing TNF-alpha, as the effect of Tax-1 was abolished by anti-TNF-alpha antibody. The expression of glutamate-catabolizing enzymes in astrocytes was increased for glutamine synthetase and decreased for glutamate dehydrogenase, the magnitudes of these effects being correlated with the level of Tax-1 transcripts. In conclusion, Tax-1 and cytokines produced by HTLV-1-infected T cells impair the ability of astrocytes to manage the steady-state level of glutamate, which in turn may affect neuronal and oligodendrocytic functions and survival.