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Mutations in Wiskott-Aldrich syndrome (WAS) protein (WASp), a regulator of actin dynamics in hematopoietic cells, cause WAS, an X-linked primary immunodeficiency characterized by recurrent infections and a marked predisposition to develop autoimmune disorders. The mechanisms that link actin alterations to the autoimmune phenotype are still poorly understood. We show that chronic activation of plasmacytoid dendritic cells (pDCs) and elevated type-I interferon (IFN) levels play a role in WAS autoimmunity. WAS patients display increased expression of type-I IFN genes and their inducible targets, alteration in pDCs numbers, and hyperresponsiveness to TLR9. Importantly, ablating IFN-I signaling in WASp null mice rescued chronic activation of conventional DCs, splenomegaly, and colitis. Using WASp-deficient mice, we demonstrated that WASp null pDCs are intrinsically more responsive to multimeric agonist of TLR9 and constitutively secrete type-I IFN but become progressively tolerant to further stimulation. By acute silencing of WASp and actin inhibitors, we show that WASp-mediated actin polymerization controls intracellular trafficking and compartmentalization of TLR9 ligands in pDCs restraining exaggerated activation of the TLR9–IFN-α pathway. Together, these data highlight the role of actin dynamics in pDC innate functions and imply the pDC–IFN-α axis as a player in the onset of autoimmune phenomena in WAS disease.

CD40/CD40 ligand (CD40L) cross-talk plays a key role in B-cell terminal maturation in the germinal centers. Genetic defects affecting CD40 cause a rare form of hyper-immunoglobulin M (IgM) syndrome, a disorder characterized by low or absent serum IgG and IgA, associated with recurrent infections. We previously reported on a few patients with homozygous CD40 mutations resulting in lack or severe reduction of CD40 cell surface expression. Here we characterize the 3 CD40 mutants due to missense mutations or small in-frame deletions, and show that the mutated proteins are synthesized but retained in the endoplasmic reticulum (ER), likely due to protein misfolding. Interestingly, the intracellular behavior and fate differ significantly among the mutants: progressive accumulation of the P2 mutant causes endoplasmic reticulum stress and the activation of an unfolded protein response; the mutant P4 is rather efficiently disposed by the ER-associated degradation pathway, while the P5 mutant partially negotiates transport to the plasma membrane, and is competent for CD40L binding. Interestingly, this latter mutant activates downstream signaling elements when overexpressed in transfected cells. These results give new important insights into the molecular pathogenesis of HIGM disease, and suggest that CD40 deficiency can also be regarded as an ER-storage disease.

CD40/CD40 ligand (CD40L) cross-talk plays a key role in B-cell terminal maturation in the germinal centers. Genetic defects affecting CD40 cause a rare form of hyper-immunoglobulin M (IgM) syndrome, a disorder characterized by low or absent serum IgG and IgA, associated with recurrent infections. We previously reported on a few patients with homozygous CD40 mutations resulting in lack or severe reduction of CD40 cell surface expression. Here we characterize the 3 CD40 mutants due to missense mutations or small in-frame deletions, and show that the mutated proteins are synthesized but retained in the endoplasmic reticulum (ER), likely due to protein misfolding. Interestingly, the intracellular behavior and fate differ significantly among the mutants: progressive accumulation of the P2 mutant causes endoplasmic reticulum stress and the activation of an unfolded protein response; the mutant P4 is rather efficiently disposed by the ER-associated degradation pathway, while the P5 mutant partially negotiates transport to the plasma membrane, and is competent for CD40L binding. Interestingly, this latter mutant activates downstream signaling elements when overexpressed in transfected cells. These results give new important insights into the molecular pathogenesis of HIGM disease, and suggest that CD40 deficiency can also be regarded as an ER-storage disease.

Autoimmune regulator (AIRE) modulates the expression of tissue-restricted antigens (TSAs) and promotes central tolerance in the thymus. However, few autoreactive T cells escape negative selection and reach the periphery, where peripheral tolerance is required to avoid autoimmunity. Murine lymph nodes (LNs) have been shown to contain “stromal” cells expressing AIRE and TSAs. Here we report the occurrence of AIRE-expressing cells in human peripheral lymphoid tissues, including LNs, tonsils, and gut-associated lymphoid tissue, with the exception of the spleen. Notably, AIRE+cells are absent in fetal LNs and, in postnatal life, they are more numerous in abdominal than in superficial LNs, thus suggesting that their development in periphery may depend on instructive signals from microenvironment and antigen challenge. Extrathymic AIRE+cells show a dendritic morphology, consistently express human leukocyte antigen-DR (HLADR) and fascin, and are largely positive for CD11c and S100 and for the dendritic cell-activation markers CD40, CD83, DC-LAMP/CD208, and CCR7. Lymphoid, myelomonocytic, mesenchymal, and epithelial cell lineage markers are negative. The HLADRhigh/AIRE+cell fraction isolated from mesenteric LNs expressed TSAs (insulin, CYP17A1, and CYP21A2), as well as molecules associated with tolerogenic functions, such as interleukin-10 and indoleamine 2,3-dioxygenase. Data indicate that AIRE+cells in human peripheral lymphoid tissues correspond to a subset of activated interdigitating dendritic cells expressing TSAs and the tolerogenic molecules indoleamine 2,3-dioxygenase and interleukin-10, suggestive of a potential tolerogenic function.

Inducible nitric oxide synthase (iNOS) is required in immune response against infections and is involved in granuloma formation in animals; in murine macrophages, iNOS is induced by lipopolysaccharide and interferon-γ. In contrast, the role of iNOS in human immune response against infections is still questioned, and its expression in granulomas is poorly investigated. Using Western blotting and immunohistochemistry, we investigated iNOS expression in human lymph nodes with nonspecific reactions and in tissues containing granulomas caused by mycobacteria, Toxoplasma, Cryptococcus neoformans, Leishmania, Bartonella, noninfectious granulomas (sarcoidosis, foreign body), and other hystiocitic reactions (Kikuchi's disease, Omenn syndrome). iNOS was undetectable in nonspecific reactive lymphadenitis, foreign-body granulomas, and Omenn syndrome, whereas it was strongly expressed in infectious granulomas, sarcoidosis, and Kikuchi's diseases. Immunohistochemistry demonstrated that iNOS was selectively expressed by the epithelioid and multinucleated giant cells within the granulomas. Use of an anti-nitrotyrosine antibody, recognizing nitrosilated amino acid residues derived from nitric oxide production, revealed a consistent positivity within the cells expressing iNOS, thus suggesting that iNOS is functionally active. Detection of cytokines by reverse transcriptase-polymerase chain reaction demonstrated that tissues that were positive for iNOS, also expressed the Th1-type cytokine interferon-γ mRNA, but not the Th2-type cytokine interleukin-4. Taken together, these results indicate that iNOS is involved in different human immune reactions characterized by histiocytic/granulomatous inflammation and associated with Th1-type cytokine secretion.

We report an 18-year-old boy with common variable immunodeficiency who presented with splenomegaly as well as left axillary and lateral cervical lymphadenopathy. Main laboratory investigations showed severe thrombocytopenia. Epstein-Barr virus (EBV) DNA was delected in the patient's throat-washing specimens and lymph node biopsy. Lymphocytes from the lymph node biopsy were also positive for EBV nuclear antigen. Serology for EBV and cytomegalovirus was negative. A therapeutic attempt with acyclovir did not influence the course of infection. Six months' treatment with human lymphoblastoid interferon-α (IFN alfa) brought about the normalization of clinical and hematologic conditions. Detection on throat-washing specimens carried out 1 year after therapy was negative. Our preliminary experience suggests that human lymphoblastoid IFN-α is a valid alternative in therapy of immunodeficient EB virus-infected patients.

Off Label Use: Off-label use of CliniMACS purified CD34+ cells.

Off Label Use: Ruxolitinib use for STAT1 GOF mutation.

The X-linked disorder Wiskott-Aldrich Syndrome (WAS), characterized by thrombocytopenia, eczema, recurrent infections, autoimmunity and cancer, is typically treated with allogeneic transplantation. Somatic gene therapy (GT) using autologous CD34+ cells is a promising treatment alternative for high-risk patients lacking matched allogeneic donors, as it avoids graft versus host disease. GT using a γ-retroviral vector with intact viral enhancers was efficacious but had a high rate of leukemia due to insertional oncogenesis. We report here preliminary results of 4 WAS patients who underwent GT using a self-inactivating lentiviral (SIN-LV) vector, in which viral enhancers have been deleted and the human WAS cDNA is controlled by a 1.6kB fragment of the human WAS promoter (w1.6_hWASP_WPRE SIN-LV). WASP expression per cell induced by this vector was lower than in normal cells when examined in murine models and human trials. We hypothesized that the SIN-LV would readily correct immune abnormalities due to selective advantage for WAS protein (WASP) expressing T cells whereas correction of myeloid and platelet abnormalities would require high vector copy number (VCN) in the infused cells.

Monoallelic gain of function (GOF) mutations in the human Signal Transducer and Activator of Transcription 1 (STAT1) manifest in immunodeficiency and autoimmunity. The immunodeficiency is caused by impaired IL-17 immunity and typically presents with chronic mucocutaneous candidiasis, variably associated with other opportunistic infections. The autoimmune manifestations due to exaggerated responsiveness to interferon are more diverse and include SLE, thyroiditis, hepatitis, and alopecia areata. The phenotypic spectrum of STAT1 GOF mutations is extremely wide, ranging from intermittent localized disease to chronic systemic illness and fatality. Allogeneic bone marrow transplantation has been attempted in severely affected patients but outcomes have been poor, leaving a void for alternate long-term strategies to control the disease and maintain remission. Recently, we diagnosed a patient suffering from chronic mucocutaneous candidiasis and life-threatening autoimmune cytopenias with a novel monoallelic mutation in the linker domain of STAT1 (c.1633G>A; p.E545K). The mutation caused a profound increase in STAT1 phosphorylation in response to type 1 and 2 interferon without affecting dephosphorylation kinetics, which is mechanistically distinct from all reported STAT1 GOF mutations to date. The potential of naïve patient CD4+T cells to become IFN- γ or IL-17 producing cells was investigated under TH0(anti-CD3/28), TH1(anti-CD3/28, IL-12) and TH17(anti-CD3/28, IL6, IL-23, TGF-β1) conditions and revealed that patient CD4+ T cells are biased to produce IFN-γ irrespective of polarizing conditions, and resistant to TH17induction upon stimulation with IL6, IL-23 and TGF-β1. In addition, the patient's proportion of T follicular helper cells (TFH) relative to regulatory T cells (Treg) was increased. Treatment with the Janus Kinase (JAK) 1/2 inhibitor Ruxolitinib reduced the hyperresponsiveness to interferon, normalized the TH1response, enabled naïve T cells to differentiate into TH17cells and decreased the TFHto Tregratio. Under therapeutic dose Ruxolitinib the patient maintained clinical remission with respect to both autoimmunity and mucocutaneous candidiasis.

Acquired hypophosphatemic rickets or osteomalacia, which is reversible after resection of tumors of soft tissues or bone (oncogenous rickets), is a rare syndrome in adults1,2 and has been reported sporadically in children.3,4 The tumor is usually detectable at the time of diagnosis of rickets. We report a case in which the tumor was found as late as four years after onset of the clinical symptoms; we also report the alterations observed in the vitamin D metabolites.Report of a Case.—In December 1978, a 13-year-old boy was admitted because of a two-year history of rickets and progressive muscular weakness. Family history was noncontributory. The child was well until the age of 11 years, when he began to complain of difficulty in climbing stairs. During hospitalization elsewhere, a diagnosis of myopathy and rickets was made, and cholecalciferol (vitamin D3) was prescribed.At admission to our department, physical examination

Off Label Use: Off-label use of CliniMACS device for purification of CD34+ bone marrow cells. Baum:Transatlantic Gene Therapy Consortium: Patents & Royalties.

No relevant conflicts of interest to declare.

Abstract 2142

Off Label Use: CliniMACS for selection of CD34+ hematopoietic cells. Baum:Patent office: Patents & Royalties.

Abstract 164FN2This icon denotes a clinically relevant abstract