Regulatory T cells decrease C3-positive reactive astrocytes in Alzheimer-like pathology.

BACKGROUND: Increasing evidence supports a key role for peripheral immune processes in the pathophysiology of Alzheimer's disease (AD), highlighting an intricate interplay between brain resident glial cells and both innate and adaptive peripheral immune effectors. We previously showed that regulatory T cells (Tregs) have a beneficial impact on disease progression in AD-like pathology, notably by modulating the microglial response associated with Aß deposits in a mouse model of amyloid pathology. Besides microglia, reactive astrocytes also play a critical role in neuroinflammatory processes associated with AD. Different phenotypes of reactive astrocytes have previously been characterized, including A1-like neurotoxic and A2-like neuroprotective subtypes. However, the precise impact of Tregs on astrocyte reactivity and phenotypes in AD still remains poorly defined. METHODS: We assessed the impact of Treg immunomodulation on astrocyte reactivity in a mouse model of AD-like amyloid pathology. Using 3D imaging, we carried out extensive morphological analyses of astrocytes following either depletion or amplification of Tregs. We further assessed the expression of several A1- and A2-like markers by immunofluorescence and RT-qPCR. RESULTS: Modulation of Tregs did not significantly impact the magnitude of global astrocyte reactivity in the brain nor in the close vicinity of cortical amyloid deposits. We did not observe changes in the number, morphology, or branching complexity of astrocytes according to immunomodulation of Tregs. However, early transient depletion of Tregs modulated the balance of reactive astrocyte subtypes, resulting in increased C3-positive A1-like phenotypes associated with amyloid deposits. Conversely, early depletion of Tregs decreased markers of A2-like phenotypes of reactive astrocytes associated with larger amyloid deposits. Intriguingly, modulation of Tregs also impacted the cerebral expression of several markers of A1-like subsets in healthy mice. CONCLUSIONS: Our study suggests that Tregs contribute to modulate and fine-tune the balance of reactive astrocyte subtypes in AD-like amyloid pathology, by dampening C3-positive astrocytes in favor of A2-like phenotypes. This effect of Tregs may partly relate to their capacity at modulating steady state astrocyte reactivity and homeostasis. Our data further highlight the need for refined markers of astrocytes subsets and strategy of analysis for better deciphering the complexity of astrocyte reactivity in neurodegeneration.

Perinatal risk factors associated with severity of haemolytic disease of the foetus and newborn due to Rhc maternal-foetal incompatibility: A retrospective cohort study.

BACKGROUND AND OBJECTIVES: Anti-c is the third red blood cell antibody responsible for haemolytic disease of the foetus and newborn (HDFN) requiring intrauterine transfusion. We aimed to identify risk factors associated with HDFN and severe HDFN due to Rhc maternal-foetal incompatibility. MATERIALS AND METHODS: A retrospective cohort study was conducted in Paris and the surrounding area (France), between 2013 and 2015. We included mothers and their children managed by the National Reference Centre in Perinatal Hemobiology for alloimmunization and maternal-foetal incompatibility for the Rhc antigen (N = 121). We conducted bivariate analyses to assess a relationship between perinatal factors (e.g., titre and concentration of anti-c antibodies, direct antiglobulin test) and HDFN, its severity and duration. RESULTS: The incidence of HDFN was 30% (n = 36), including 11% of severe HDFN (n = 13). Seven percent (n = 9) of neonates received at least one transfusion during the first week and 21% (n = 26) after this period until 3 weeks of life. During pregnancy, a concentration ≥7.5 IU/ml and a titre ≥4 and above were associated with HDFN and severe HDFN (p < 0.05). At birth, the high intensity of the quantitative direct antiglobulin test was associated with HDFN and severe HDFN (p < 0.05). A concentration ≥15 IU/ml is the best factor (area under curve [AUC] = 0.78) in predicting HDFN, followed by a titre ≥8 (AUC = 0.76). CONCLUSION: Anti-c alloimmunization causes neonatal anaemia, which is often belated. Paediatricians have to be aware of these risk factors and organize prolonged monitoring of neonates.

Insights into anti-D formation in carriers of RhD variants through studies of 3D intraprotein interactions.

BACKGROUND: Many RhD variants associated with anti-D formation (partial D) in carriers exposed to the conventional D antigen carry mutations affecting extracellular loop residues. Surprisingly, some carry mutations affecting transmembrane or intracellular domains, positions not thought likely to have a major impact on D epitopes. STUDY DESIGN AND METHODS: A wild-type Rh trimer (RhD1 RhAG2 ) was modeled by comparative modeling with the human RhCG structure. Taking trimer conformation, residue accessibility, and position relative to the lipid bilayer into account, we redefine the domains of the RhD protein. We generated models for RhD variants carrying one or two amino acid substitutions associated with anti-D formation in published articles (25 variants) or abstracts (12 variants) and for RHD*weak D type 38. We determined the extracellular substitutions and compared the interactions of the variants with those of the standard RhD. RESULTS: The findings of the three-dimensional (3D) analysis were correlated with anti-D formation for 76% of RhD variants: 15 substitutions associated with anti-D formation concerned extracellular residues, and structural differences in intraprotein interactions relative to standard RhD were observed in the others. We discuss the mechanisms by which D epitopes may be modified in variants in which the extracellular residues are identical to those of standard RhD and provide arguments for the benignity of p.T379M (RHD*DAU0) and p.G278D (RHD*weak D type 38) in transfusion medicine. CONCLUSION: The study of RhD intraprotein interactions and the precise redefinition of residue accessibility provide insight into the mechanisms through which RhD point mutations may lead to anti-D formation in carriers.

Clinical input of anti-D quantitation by continuous-flow analysis on autoanalyzer in the management of high-titer anti-D maternal alloimmunization.

BACKGROUND: In addition to titration by indirect antiglobulin test most widely used, anti-D quantitation by continuous-flow analysis (CFA) may be performed to assess severity of maternal immunization. Only five studies have reported its added value in the management of pregnancies complicated by anti-D immunization. STUDY DESIGN AND METHODS: A retrospective study of 74 severe anti-D-immunized pregnancies was conducted from January 1, 2013, to December 31, 2014, in the Trousseau Hospital in Paris (France). Concentration of maternal anti-D was measured by titration and by CFA two-stages method (2SM; total amount of anti-D) and one-stage method (1SM; high-affinity IgG1 anti-D). These biologic data were analyzed according to the severity of the hemolytic disease of the fetus and the newborn. RESULTS: The value of 5 IU anti-D/mL in maternal serum is validated as a threshold to trigger ultrasonographic and Doppler fetal close follow-up. A high 1SM/2SM ratio was associated with a higher risk of intrauterine transfusion (IUT). For pregnancies requiring IUT and without increasing titer, maternal 1SM anti-D concentration tends to correlate with the precocity of fetal anemia. In the "without-IUT" group 1SM and 2SM anti-D concentrations correlate significantly with cord bilirubin levels of the newborn at birth. CONCLUSION: Altogether our results underline the importance of anti-D quantitation by CFA to optimize the management of anti-D-alloimmunized pregnancies.

Regulatory T cells delay disease progression in Alzheimer-like pathology.

Recent studies highlight the implication of innate and adaptive immunity in the pathophysiology of Alzheimer's disease, and foster immunotherapy as a promising strategy for its treatment. Vaccines targeting amyloid-ß peptide provided encouraging results in mouse models, but severe side effects attributed to T cell responses in the first clinical trial AN1792 underlined the need for better understanding adaptive immunity in Alzheimer's disease. We previously showed that regulatory T cells critically control amyloid-ß-specific CD4(+) T cell responses in both physiological and pathological settings. Here, we analysed the impact of regulatory T cells on spontaneous disease progression in a murine model of Alzheimer's disease. Early transient depletion of regulatory T cells accelerated the onset of cognitive deficits in APPPS1 mice, without altering amyloid-ß deposition. Earlier cognitive impairment correlated with reduced recruitment of microglia towards amyloid deposits and altered disease-related gene expression profile. Conversely, amplification of regulatory T cells through peripheral low-dose IL-2 treatment increased numbers of plaque-associated microglia, and restored cognitive functions in APPPS1 mice. These data suggest that regulatory T cells play a beneficial role in the pathophysiology of Alzheimer's disease, by slowing disease progression and modulating microglial response to amyloid-ß deposition. Our study highlights the therapeutic potential of repurposed IL-2 for innovative immunotherapy based on modulation of regulatory T cells in Alzheimer's disease.

MHC-independent genetic factors control the magnitude of CD4+ T cell responses to amyloid-ß peptide in mice through regulatory T cell-mediated inhibition.

Accumulation of amyloid-ß peptide (Aß) is considered the triggering factor of pathogenic lesions in Alzheimer's disease (AD), and vaccines targeting Aß are promising therapeutic options. However, the occurrence of meningoencephalitides attributed to T cell responses in 6% of Aß-immunized patients underscores the need for a better understanding of T cell responses to Aß. We characterized the parameters controlling the magnitude of Aß-specific CD4(+) T cell responses in mice. T cell responsiveness to Aß1-42 was highly heterogeneous between mouse strains of different H-2 haplotypes, with SJL/J (H-2(s)) mice displaying a strong response, mainly specific for Aß10-24, and C57BL/6 (H-2(b)) mice displaying a weak response to Aß16-30. Surprisingly, C57BL/6 mice congenic for the H-2(s) haplotype (B6.H-2(S)), which display a "permissive" MHC class II allele for presentation of the immunodominant Aß10-24 epitope, showed a very weak CD4(+) T cell response to Aß, suggesting that MHC-independent genes downmodulate Aß-specific CD4(+) T cell responses in C57BL/6 background. Vaccine-induced CD4(+) T cell responses to Aß were significantly enhanced in both C57BL/6 and B6.H-2(S) mice upon depletion of regulatory T cells (Tregs), whereas Treg-depleted SJL/J mice displayed unaltered Aß-specific T cell responses. Finally, Treg depletion in C57BL/6 transgenic APPPS1 mice, a mouse model of AD, results in enhanced vaccine-induced CD4(+) T cell responses in AD compared with wild-type animals. We concluded that the magnitude of Aß-specific CD4(+) T cell responses is critically controlled in both physiological and pathological settings by MHC-independent genetic factors that determine the overall potency of Aß-specific Treg responses.

Acute renal failure with lambda light chain-derived crystals in a patient with IgD myeloma.

Kidney involvement with immunoglobulin crystals usually relates to a light chain of the kappa type, in MGUS or smoldering myeloma, frequently causing Fanconi's syndrome with progressive renal insufficiency. We report on a case with severe myeloma featuring lambda light chain-derived crystals and acute kidney injury. Histology showed acute tubular necrosis and tubule obstruction with crystals, which were also abundant inside tubule epithelial cells, macrophages and bone marrow plasma cells. The light chain variable domain had a normal overall primary structure but included 11 somatic mutations, 3 of which likely increased the surface hydrophobicity, as observed in previously reported kappa-type crystals.

Effect of intravenous immunoglobulins to postpone the gestational age of first intrauterine transfusion in very severe red blood cell alloimmunization: A case-control study.

BACKGROUND: Early intrauterine transfusion (IUT) is associated with a higher risk of fetal loss. Our objective was to evaluate the efficiciency of intravenous immunoglobulins (IVIG) to postpone the gestational age at first IUT beyond 20 weeks of gestation (WG) compared to the previous pregnancy in case of very severe red blood cell (RBC) alloimmunization. STUDY DESIGN AND METHODS: Very severe RBC alloimmunization was defined by a high titer of antibodies and a previous pregnancy complicated by a first IUT before 24 WG and/or perinatal death directly related to alloimmunization. We performed a single-center case-control study. Cases and controls were patients respectively treated with weekly IVIG infusions started before 13 WG, and without. RESULTS: Twenty cases and 21 controls were included. Gestational age (GA) at first IUT was postponed after 20 WG in 18/20 (90 %) of patients treated with IVIG and in 15/21 (71 %) in the control group (p = 0.24). Compared to the previous pregnancy, the GA at first IUT was postponed by a median of 22 [+11; +49] days in the IVIG group and occurred in average 2 days earlier [-17 ; +12] in the non-treated group (p = 0.02). There was no difference between number of IUT and need for exchange-transfusion. IVIG treatment was associated with a significant decrease of antibodies' quantitation. CONCLUSION: In our series, IVIG tends to differ first IUT beyond 20 WG and have a significant effect in postponing the gestational age of the first IUT in patients with very severe RBC alloimmunization.

Reduced fetal movement during pregnancy: Is the Kleihauer-Betke test really useful?

INTRODUCTION: Reduced fetal movement (rFM) is a frequent cause of consultation during the pregnancy and can reveal feto-maternal hemorrhage (FMH) that is sometimes responsible of severe fetal anemia. Our primary objective was to evaluate the contribution of the KBT in case of rFM. Our secondary objective was to compare it with ultrasound examination including peak systolic velocity of the middle cerebral artery (MCA-PSV) to predict neonatal anemia. MATERIALS AND METHODS: We conducted a retrospective study from January 2016 to December 2017 at Armand-Trousseau Hospital in Paris. We analyzed all patients consulting for rFM from 18 to 41 weeks of gestation. We compared the performance of KBT and MCA-PSV to predict neonatal anemia (Hemoglobin at birth under 13.5 g/dL) and severe neonatal anemia (Hb < 10 g/dL). RESULTS: Among the 338 patients, 327 KBT (96.7%) were performed. KBT was found positive in three cases (0.9%). Only one neonate (0.3%) presented with severe anemia requiring a postnatal transfusion. MCA-PSV was performed in 166 cases (49.1%). KBT and MCA-PSV were significantly correlated with neonatal hemoglobin at birth. KBT was better than MCA-PSV to predict neonatal anemia, while MCA-PSV was better than KBT to predict moderate to severe anemia. The KBT and MCA-PSV Doppler had excellent sensitivity and predictive negative values (100%), but they had poor predictive positive values for severe neonatal anemia. CONCLUSION: In case of decreased fetal movement, we suggest performing fetal cerebral Doppler. MCA-PSV could suffice in first approach. KBT may be performed if there is suspicion of fetal anemia in order to confirm FMH.

High titers of autoantibodies in patients with sickle-cell disease.

OBJECTIVE: Frequency and titers of autoantibodies in patients with sickle-cell disease (SCD) have been reported as relatively high. In a prospective study of 88 patients, we examined this "hyper-autoreactivity" and its clinical consequences. METHODS: For 1 year, patients with SCD were screened for the presence in their serum of antinuclear, anti-double-stranded DNA, antiextractible nuclear antigens, anticardiolipin antibodies, and rheumatoid factors. A population of 85 sex-matched individuals of similar ethnic origin served as controls. RESULTS: Whereas prevalence of autoantibodies did not differ between the 2 groups, the type and rate of antinuclear antibodies were different. Autoantibodies from the SCD patients showed various immunofluorescence patterns, whereas only speckled patterns at low titers were present in controls. No antibody specificity was found in either group. SCD patients and controls displayed similar rates of anticardiolipin antibodies, but the SCD patients tended to be more frequently positive for rheumatoid factors. Six-year followup of the SCD patients did not provide any clinical evidence for onset of an autoimmune disease, except for 1 patient who developed rheumatoid arthritis, with increasing antinuclear antibodies followed by emergence of specific markers 5 years later. CONCLUSION: Patients with SCD displayed high titers of autoantibodies. This observation may be due only to immune activation and/or dysfunction in SCD, as neither pathogenic specificity of autoantibodies nor autoimmune clinical signs appeared in the majority of cases in our study.