THU0053 CONTRIBUTION OF DEFECTIVE NON-APOPTOTIC FAS SIGNALING TO IMMUNE DYSREGULATION IN AUTOIMMUNE LYMPHOPROLIFERATIVE SYNDROME (ALPS)

Background:

ALPS patients show impaired generation of humoral memory for T independent antigens whereas they generate memory for self-antigens due to impaired FAS-dependent removal of autoreactive germinal center B cells. It is known that FAS signaling via caspase activation results in cell apoptosis. However, FAS ligation may also initiate or modulate non-apoptotic signaling as shown for example by its ability to activate NF-κB. Recent data implicate a regulatory role of FAS in the modulation of mTOR signaling in ALPS double-negative T cells. Moreover, a recently described C194V FAS mutation disturbs its post-translational modification leading to impaired apoptosis induction while non-apoptotic signalling is still intact. Consequently, C194V FAS protects from the autoimmune phenotype in the murine ALPS system. This supports the view that FAS may prevent autoimmunity with other mechanisms than inducing apoptosis.

Objectives:

We hypothesize that FAS mutations impair this modulatory signaling, leading to hyper-activation of B cells. Therefore we aim to investigate non apoptotic FAS signaling in B cells derived from healthy individuals and ALPS patients.

Methods:

We studied resting and activated B cells in ALPS patients in presence or absence of FAS ligand by flow cytometry analysing relevant molecules to the CD40 signaling pathway. We used mass cytometry to perform functional phenotyping of B cells isolated from secondary lymphoid organs. Proteomic studies were performed to identify potential signaling circuits and RNA sequencing to study the consequences of FAS signaling on B cell fate.

Results:

In CD40L activated B cells, FAS signaling results in specific modulation of the mTOR signaling pathway. This modulation is absent in ALPS derived B cells. In line with these data germinal center B cells and plasmablast from secondary lymphoid organs of ALPS patients show hyperactive mTOR signaling pathway. Proteomic studies identify a circuit that links FAS to the phosphatase PTEN via DAXX and the deubiquitinase USP7.

Conclusion:

We describe a new role of FAS in the regulation of B cell activation. Defects in FAS signaling in ALPS contribute to dysregulation of the mTOR signaling pathway and disturbed B cell development.

Disclosure of Interests:

None declared

Common Variable Immunodeficiency: Epidemiology, Pathogenesis, Clinical Manifestations, Diagnosis, Classification, and Management

Common variable immunodeficiency (CVID) is a heterogeneous disorder characterized by hypogammaglobulinemia and increased susceptibility to recurrent bacterial infections. It is the most frequent symptomatic antibody deficiency, with a wide variety of infectious and noninfectious complications. Numerous studies have demonstrated that immunological and genetic defects are involved in the pathogenesis of CVID. However, in most cases, the genetic background of the disease remains unidentified. This review aims to discuss various aspects of CVID, including epidemiology, pathogenesis, symptoms, diagnosis, classification, and management.

Recurrent infective endocarditis due to Aggregatibacter aphrophilus and Staphylococcus lugdunensis

Uncommon microorganisms are increasingly being recognized as causative agents of paediatric infectious endocarditis (IE). We report a 4-year old girl with congenital heart disease, who suffered from 2 IE episodes secondary to Aggregatibacter aphrophilus (formerly Haemophilus aphrophilus) and Staphylococcus lugdunensis, both rarely reported pathogens in this age group. The patient was initially successfully treated with prolonged intravenous antibiotic courses, however removal of the Contegra valved conduit during the second episode was required due to recurrence of fever and development of pulmonary embolism despite completion of antibiotic therapy. A. aphrohilus is a member of the fastidious gram negative microorganisms of the HACEK group (Haemophilus spp., Aggregatibacter spp, Cardiobaterium hominis, Eikenella corrodens and Kingella kingae), that colonize the oropharynx and are a recognised cause of IE. Prognosis of children with IE due to HACEK group members varies, half of them suffering from complications and mortality rates of 10-12.5%. Although S. lugdunensis belongs to coagulase negative staphylococci (CONS), it behaves more like S. aureus species rather than CONS. This microorganism is a well-described cause of endocarditis in adult patients, associated with high requirements of surgical procedures and mortality (42-78%). In conclusion, paediatric IE can be caused by uncommon microorganisms associated with severe complications and potential fatality. The isolation of S. lugdunensis or A. aphrophilus in febrile patients should be considered clinically relevant and cardiac involvement must be ruled out. Those patients with proved IE will require prolonged intravenous antibiotic courses and in complicated cases surgical intervention.

Room-temperature high-frequency transport of dirac fermions in epitaxially grown Sb2Te3- and Bi2Te3-based topological insulators

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Catheter-related Mycobacterium fortuitum bloodstream infection: rapid identification using MALDI-TOF mass spectrometry

We present the case of a 6-year-old boy diagnosed with stage III mediastinal Non Hodgkin Lymphoblastic T cell Lymphoma who suffered from catheter-related bloodstream infection (CRBI) due to Mycobacterium fortuitum whilst receiving chemotherapy. Isolation of this rare pathogen was done directly from blood culture and identification was made rapidly within 48 h using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectro-metry as well as specific polymerase chain reaction (PCR)-reverse hybridization method. This allowed prompt directed antibiotic therapy apart from central venous catheter removal and resulted in an excellent clinical response. This case highlights the potential benefit of using MALDI-TOF mass spectrometry, a fast, cost-effective and precise methodology, in the diagnosis and subsequent management of invasive bacterial infection.

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Terahertz radiation driven chiral edge currents in graphene

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Dynamic Hall effect driven by circularly polarized light in a graphene layer

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Orbital photogalvanic effects in quantum-confined structures

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Ratchet effects induced by terahertz radiation in heterostructures with a lateral periodic potential

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Spin currents in diluted magnetic semiconductors

We study zero-bias spin separation in (Cd,Mn)Te/(Cd,Mg)Te diluted magnetic semiconductor structures. The spin current generated by electron gas heating under terahertz radiation is converted into a net electric current by applying an external magnetic field. The experiments show that the spin polarization of the magnetic ion system enhances drastically the conversion process due to giant Zeeman splitting of the conduction band and spin-dependent electron scattering on localized Mn(2+) ions.

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