Autoimmunity and immunodeficiency associated with monoallelic LIG4 mutations via haploinsufficiency.

BACKGROUND: Biallelic mutations in LIG4 encoding DNA-ligase 4 cause a rare immunodeficiency syndrome manifesting as infant-onset life-threatening and/or opportunistic infections, skeletal malformations, radiosensitivity and neoplasia. LIG4 is pivotal during DNA repair and during V(D)J recombination as it performs the final DNA-break sealing step. OBJECTIVES: This study explored whether monoallelic LIG4 missense mutations may underlie immunodeficiency and autoimmunity with autosomal dominant inheritance. METHODS: Extensive flow-cytometric immune-phenotyping was performed. Rare variants of immune system genes were analyzed by whole exome sequencing. DNA repair functionality and T-cell-intrinsic DNA damage tolerance was tested with an ensemble of in vitro and in silico tools. Antigen-receptor diversity and autoimmune features were characterized by high-throughput sequencing and autoantibody arrays. Reconstitution of wild-type versus mutant LIG4 were performed in LIG4 knockout Jurkat T cells, and DNA damage tolerance was subsequently assessed. RESULTS: A novel heterozygous LIG4 loss-of-function mutation (p.R580Q), associated with a dominantly inherited familial immune-dysregulation consisting of autoimmune cytopenias, and in the index patient with lymphoproliferation, agammaglobulinemia, and adaptive immune cell infiltration into nonlymphoid organs. Immunophenotyping revealed reduced naive CD4+ T cells and low TCR-Vα7.2+ T cells, while T-/B-cell receptor repertoires showed only mild alterations. Cohort screening identified 2 other nonrelated patients with the monoallelic LIG4 mutation p.A842D recapitulating clinical and immune-phenotypic dysregulations observed in the index family and displaying T-cell-intrinsic DNA damage intolerance. Reconstitution experiments and molecular dynamics simulations categorize both missense mutations as loss-of-function and haploinsufficient. CONCLUSIONS: This study provides evidence that certain monoallelic LIG4 mutations may cause human immune dysregulation via haploinsufficiency.

Tumor-derived TGF-ß inhibits mitochondrial respiration to suppress IFN-γ production by human CD4+ T cells.

Transforming growth factor-ß (TGF-ß) is produced by tumors, and increased amounts of this cytokine in the tumor microenvironment and serum are associated with poor patient survival. TGF-ß-mediated suppression of antitumor T cell responses contributes to tumor growth and survival. However, TGF-ß also has tumor-suppressive activity; thus, dissecting cell type-specific molecular effects may inform therapeutic strategies targeting this cytokine. Here, using human peripheral and tumor-associated lymphocytes, we investigated how tumor-derived TGF-ß suppresses a key antitumor function of CD4+ T cells, interferon-γ (IFN-γ) production. Suppression required the expression and phosphorylation of Smad proteins in the TGF-ß signaling pathway, but not their nuclear translocation, and depended on oxygen availability, suggesting a metabolic basis for these effects. Smad proteins were detected in the mitochondria of CD4+ T cells, where they were phosphorylated upon treatment with TGF-ß. Phosphorylated Smad proteins were also detected in the mitochondria of isolated tumor-associated lymphocytes. TGF-ß substantially impaired the ATP-coupled respiration of CD4+ T cells and specifically inhibited mitochondrial complex V (ATP synthase) activity. Last, inhibition of ATP synthase alone was sufficient to impair IFN-γ production by CD4+ T cells. These results, which have implications for human antitumor immunity, suggest that TGF-ß targets T cell metabolism directly, thus diminishing T cell function through metabolic paralysis.

Detection of Sp110 by Flow Cytometry and Application to Screening Patients for Veno-occlusive Disease with Immunodeficiency.

Mutations in Sp110 are the underlying cause of veno-occlusive disease with immunodeficiency (VODI), a combined immunodeficiency that is difficult to treat and often fatal. Because early treatment is critically important for patients with VODI, broadly usable diagnostic tools are needed to detect Sp110 protein deficiency. Several factors make establishing the diagnosis of VODI challenging: (1) Current screening strategies to identify severe combined immunodeficiency are based on measuring T cell receptor excision circles (TREC). This approach will fail to identify VODI patients because the disease is not associated with severe T cell lymphopenia at birth; (2) the SP110 gene contains 17 exons, making it a challenge for Sanger sequencing. The recently developed next-generation sequencing (NGS) platforms that can rapidly determine the sequence of all 17 exons are available in only a few laboratories; (3) there is no standard functional assay to test for the effects of novel mutations in Sp110; and (4) it has been difficult to use flow cytometry to identify patients who lack Sp110 because of the low level of Sp110 protein in peripheral blood lymphocytes. We report here a novel flow cytometric assay that is easily performed in diagnostic laboratories and might thus become a standard assay for the evaluation of patients who may have VODI. In addition, the assay will facilitate investigations directed at understanding the function of Sp110.

Characteristics of autoantibodies targeting 14-3-3 proteins and their association with clinical features in newly diagnosed giant cell arteritis.

Objectives: Autoantibodies are useful biomarkers for diagnosing and monitoring treatment in some autoimmune diseases. Antibodies against isoforms of 14-3-3 protein have been proposed as biomarkers for the presence of aortic aneurysm in large-vessel vasculitis (LVV). Here, we aimed to evaluate the diagnostic role and potential immunopathological involvement of anti-14-3-3 antibodies in newly diagnosed LVV patients. Methods: Antibodies against three isoforms of 14-3-3 (γ, ɛ and ζ) were measured in 90 subjects: 48 GCA and 3 Takayasu's arteritis (TA) patients, and 39 controls (non-inflammatory and inflammatory diseases), using a multiplexed bead-based immunoassay and immunoprecipitation studies. The positive cut-off value was defined based on young healthy controls. Anti-14-3-3 IgG antibodies in LVV patients were compared with those in controls in order to assess their diagnostic performance, and the relationship of anti-14-3-3 IgG antibodies to the immunohistopathology of artery explants was assessed. Results: Antibodies against all three 14-3-3 isoforms were detected in LVV patients as well as in age-matched inflammatory and non-inflammatory controls. Among LVV patients, detection of antibodies targeting 14-3-3 ɛ and ζ was associated with more severe disease. Detection of antibodies against 14-3-3 γ was linked to latent Toxoplasma gondii infection, a parasite that secrets a 14-3-3 homologue, suggesting potential cross-reactivity. Conclusion: Detection of antibodies against 14-3-3 proteins at the time of LVV diagnosis is not disease-specific. Their presence at high levels in LVV patients with stroke, aortitis and-in a previous study-aneurysm formation may indicate an association with extensive tissue destruction. The relevance of 14-3-3 antibodies in non-LVV patients needs to be investigated in larger cohorts.

Stress-Induced In Vivo Recruitment of Human Cytotoxic Natural Killer Cells Favors Subsets with Distinct Receptor Profiles and Associates with Increased Epinephrine Levels.

BACKGROUND: Acute stress drives a 'high-alert' response in the immune system. Psychoactive drugs induce distinct stress hormone profiles, offering a sought-after opportunity to dissect the in vivo immunological effects of acute stress in humans. METHODS: 3,4-methylenedioxymethamphetamine (MDMA), methylphenidate (MPH), or both, were administered to healthy volunteers in a randomized, double-blind, placebo-controlled crossover-study. Lymphocyte subset frequencies, natural killer (NK) cell immune-phenotypes, and changes in effector function were assessed, and linked to stress hormone levels and expression of CD62L, CX3CR1, CD18, and stress hormone receptors on NK cells. RESULTS: MDMA/MPH > MDMA > MPH robustly induced an epinephrine-dominant stress response. Immunologically, rapid redistribution of peripheral blood lymphocyte-subsets towards phenotypically mature NK cells occurred. NK cytotoxicity was unaltered, but they expressed slightly reduced levels of the activating receptor NKG2D. Preferential circulation of mature NK cells was associated with high epinephrine receptor expression among this subset, as well as expression of integrin ligands previously linked to epinephrine-induced endothelial detachment. CONCLUSION: The acute epinephrine-induced stress response was characterized by rapid accumulation of mature and functional NK cells in the peripheral circulation. This is in line with studies using other acute stressors and supports the role of the acute stress response in rapidly mobilizing the innate immune system to counteract incoming threats.

CEACAM1 induces B-cell survival and is essential for protective antiviral antibody production.

B cells are essential for antiviral immune defence because they produce neutralizing antibodies, present antigen and maintain the lymphoid architecture. Here we show that intrinsic signalling of CEACAM1 is essential for generating efficient B-cell responses. Although CEACAM1 exerts limited influence on the proliferation of B cells, expression of CEACAM1 induces survival of proliferating B cells via the BTK/Syk/NF-κB-axis. The absence of this signalling cascade in naive Ceacam1(-/-) mice limits the survival of B cells. During systemic infection with cytopathic vesicular stomatitis virus, Ceacam1(-/-) mice can barely induce neutralizing antibody responses and die early after infection. We find, therefore, that CEACAM1 is a crucial regulator of B-cell survival, influencing B-cell numbers and protective antiviral antibody responses.