We documented and analyzed moth fly occurrence and spread of multidrug-resistant bacteria in a tertiary care hospital in Germany. The moth flies (Clogmia albipunctata) bred in the sewage system, then ...moved into the hospital, carrying biofilm and multidrug-resistant bacteria on their feet. Subsequently, the hospital developed a pest control protocol.
Griscelli syndrome (GS) was diagnosed in a 2-year-old patient with oculocutaneous albinism and immunodeficiency, but sequencing of RAB27a revealed only a heterozygous mutation. Due to impaired ...natural killer (NK) and T-cell cytotoxicity implying a high risk of developing hemophagocytic lymphohistiocytosis (HLH), he was prepared for hematopoietic stem cell transplantation (HSCT). Unexpectedly, a severe bleeding episode occurred that led to the demonstration of disturbed platelet aggregation, reduced plateletdense granules, and impaired platelet degranulation. In combination with neutropenia, this suggested the diagnosis of Hermansky-Pudlak syndrome type II (HPSII) and a novel homozygous mutation in AP3B1 was detected. None of the 3 reported HPSII patients had developed HLH, and our patient seroconverted to Epstein-Barr virus (EBV) without clinical symptoms. HSCT was therefore withheld, and granulocyte-colony-stimulating factor (G-CSF) therapy was initiated and prevented further bacterial infections. At 3 years of age, however, the patient developed, without an obvious trigger, fulminant HLH that was resistant to therapy. This patient shows that careful clinical and molecular diagnosis is essential to differentiate the complex disorders of lysosomal trafficking. HPSII belongs to the group of familial hemophagocytic syndromes and may represent an indication for HSCT. (Blood. 2006;108:81-87)
Inherited defects in MyD88 and IRAK4, two regulators in Toll-like receptor (TLR) signaling, are clinically highly relevant, but still incompletely understood. MyD88- and IRAK4-deficient patients are ...exceedingly susceptible to a narrow spectrum of pathogens, with ∼50% lethality in the first years of life. To better understand the underlying molecular and cellular characteristics that determine disease progression, we aimed at modeling the cellular response to pathogens
. To this end, we determined the immunophenotype of monocytes and macrophages derived from MyD88- and IRAK4-deficient patients. We recognized that macrophages derived from both patients were particularly poorly activated by streptococci, indicating that both signaling intermediates are essential for the immune response to facultative pathogens. To characterize this defect in more detail, we generated induced pluripotent stem cells (iPSCs) of fibroblasts derived from an MyD88-deficient patient. The underlying genetic defect was corrected using
transposon vectors encoding either the long (L) or the short (S)
isoform, respectively. Macrophages derived from these iPSC lines (iMacs) expressed typical macrophage markers, stably produced either MyD88 isoform, and showed robust phagocytic activity. Notably, iMacs expressing MyD88-L, but not MyD88-S, exhibited similar responses to external stimuli, including cytokine release patterns, as compared to genetically normal iMacs. Thus, the two MyD88 isoforms assume distinct functions in signaling. In conclusion, iPSC technology, in combination with efficient myeloid differentiation protocols, provides a valuable and inexhaustible source of macrophages, which can be used for disease modeling. Moreover, iPSC-derived macrophages may eventually aid in stabilizing MyD88-deficient patients during pyogenic infections.
Fas is a transmembrane receptor involved in the maintenance of tolerance and immune homeostasis. In murine models, it has been shown to be essential for deletion of autoreactive B cells in the ...germinal center. The role of Fas in human B-cell selection and in development of autoimmunity in patients carrying FAS mutations is unclear. We analyzed patients with either a somatic FAS mutation or a germline FAS mutation and somatic loss-of-heterozygosity, which allows comparing the fate of B cells with impaired vs normal Fas signaling within the same individual. Class-switched memory B cells showed: accumulation of FAS-mutated B cells; failure to enrich single V, D, J genes and single V-D, D-J gene combinations of the B-cell receptor variable region; increased frequency of variable regions with higher content of positively charged amino acids; and longer CDR3 and maintenance of polyreactive specificities. Importantly, Fas-deficient switched memory B cells showed increased rates of somatic hypermutation. Our data uncover a defect in B-cell selection in patients with FAS mutations, which has implications for the understanding of the pathogenesis of autoimmunity and lymphomagenesis of autoimmune lymphoproliferative syndrome.
•Fas-mutated B cells accumulate in the memory compartment and are highly mutated and polyreactive.•Fas deficiency leads to an intrinsic defect in B cells selection that predisposes to autoimmunity and identifies B cells as therapeutic targets for autoimmune lymphoproliferative syndrome.
...we compared expression levels of ORAI and STIM homologues between PMNs, B lymphocytes, and T lymphocytes by using publicly available RNA sequencing data from healthy subjects.7 ORAI1 and STIM1 ...were similarly expressed in PMNs and lymphocytes. ...mRNA levels of the different ORAI and STIM homologues are comparable across leukocyte subsets (see Fig E1 in this article's Online Repository at www.jacionline.org). ...FcγRIII (CD16) cross-linking also induced Ca2+ influx in ORAI1 p.R91W PMN that was only moderately reduced compared with that in control PMNs (see Fig E4 in this article's Online Repository at www.jacionline.org). Because cytosolic Ca2+ concentrations are considered essential for antibacterial PMN functions, we examined whether ORAI1 deficiency impaired the PMN response to various microbial and nonmicrobial ligands.
Repair of DNA double-strand breaks (DSBs) by the nonhomologous end-joining pathway (NHEJ) is important not only for repair of spontaneous breaks but also for breaks induced in developing lymphocytes ...during V(D)J (variable V, diversity D, and joining J genes) recombination of their antigen receptor loci to create a diverse repertoire. Mutations in the NHEJ factor XLF result in extreme sensitivity for ionizing radiation, microcephaly, and growth retardation comparable to mutations in LIG4 and XRCC4, which together form the NHEJ ligation complex. However, the effect on the immune system is variable (mild to severe immunodeficiency) and less prominent than that seen in deficiencies of NHEJ factors ARTEMIS and DNA-dependent protein kinase catalytic subunit, with defects in the hairpin opening step, which is crucial and unique for V(D)J recombination. Therefore, we aimed to study the role of XLF during V(D)J recombination. We obtained clinical data from 9 XLF-deficient patients and performed immune phenotyping and antigen receptor repertoire analysis of immunoglobulin (Ig) and T-cell receptor (TR) rearrangements, using next-generation sequencing in 6 patients. The results were compared with XRCC4 and LIG4 deficiency. Both Ig and TR rearrangements showed a significant decrease in the number of nontemplated (N) nucleotides inserted by terminal deoxynucleotidyl transferase, which resulted in a decrease of 2 to 3 amino acids in the CDR3. Such a reduction in the number of N-nucleotides has a great effect on the junctional diversity, and thereby on the total diversity of the Ig and TR repertoire. This shows that XLF has an important role during V(D)J recombination in creating diversity of the repertoire by stimulating N-nucleotide insertion.
•XLF belongs to the NHEJ ligation complex and has a dual role in DNA double-strand break repair and V(D)J recombination.•XLF is involved in N-nucleotide addition, and thereby contributes to junctional diversity of the antigen receptors.
To evaluate the occurrence of autoimmune and inflammatory complications in Wiskott-Aldrich syndrome (WAS) and to determine risk factors and the prognosis of such complications with the aim of ...improving the definition of treatment options.
We reviewed the records of 55 patients with WAS evaluated at Necker-Enfants Malades Hospital (Paris) from 1980 to 2000.
Forty patients (72%) had at least 1 autoimmune or inflammatory complication. Autoimmune hemolytic anemia was detected in 20 cases (36%); in all cases, onset occurred before the age of 5 years. Other complications included neutropenia (25%), arthritis (29%), skin vasculitis (22%), cerebral vasculitis (7%), inflammatory bowel disease (9%), and renal disease (3%). The median survival of the entire population was 14.5 years. Two autoimmune complications and 1 biological factor were predictive of a poor prognosis in this population: autoimmune hemolytic anemia, severe thrombocytopenia recurring after splenectomy, and high serum immunoglobulin M (IgM) levels before splenectomy. Autoimmune hemolytic anemia was significantly more observed in patients with high serum IgM level.
High serum IgM concentration before splenectomy was identified as a risk factor for autoimmune hemolytic anemia; however, it must be confirmed. Autoimmune hemolytic anemia and severe thrombocytopenia recurring after splenectomy were 2 indicators of a poor prognosis. Those results suggest that patients with WAS and IgM levels more than mean + 2 standard deviations before splenectomy should be placed under strict surveillance. Furthermore, severe autoimmune complications should lead, as early as possible, to hematopoietic stem cell transplantation using the best available donor.
Artemis protein has irreplaceable functions in V(D)J recombination and nonhomologous end joining (NHEJ) as a hairpin and 5′ and 3′ overhang endonuclease. The kinase activity of the DNA-dependent ...protein kinase catalytic subunit (DNA-PKcs) is necessary in activating Artemis as an endonuclease. Here we report that three basal phosphorylation sites and 11 DNA-PKcs phosphorylation sites within the mammalian Artemis are all located in the C-terminal domain. All but one of these phosphorylation sites deviate from the SQ or TQ motif of DNA-PKcs that was predicted previously from in vitro phosphorylation studies. Phosphatase-treated mammalian Artemis and Artemis that is mutated at the three basal phosphorylation sites still retain DNA-PKcs-dependent endonucleolytic activities, indicating that basal phosphorylation is not required for the activation. In vivo studies of Artemis lacking the C-terminal domain have been reported to be sufficient to complement V(D)J recombination in Artemis null cells. Therefore, the C-terminal domain may have a negative regulatory effect on the Artemis endonucleolytic activities, and phosphorylation by DNA-PKcs in the C-terminal domain may relieve this inhibition.
Deficiency of Adenosine Deaminase Type 2 (DADA2) is a rare autosomal recessive inherited disorder with a variable phenotype including generalized or cerebral vasculitis and bone marrow failure. It is ...caused by variations in the adenosine deaminase 2 gene (
ADA2
), which leads to decreased adenosine deaminase 2 enzyme activity. Here we present three instructive scenarios that demonstrate DADA2 spectrum characteristics and provide a clear and thorough diagnostic and therapeutic workflow for effective patient care. Patient 1 illustrates cerebral vasculitis in DADA2. Genetic analysis reveals a compound heterozygosity including the novel
ADA2
variant, p.V325Tfs
*
7. In patient 2, different vasculitis phenotypes of the DADA2 spectrum are presented, all resulting from the homozygous
ADA2
mutation p.Y453C. In this family, the potential risk for siblings is particularly evident. Patient 3 represents pure red cell aplasia with bone marrow failure in DADA2. Here, ultimately, stem cell transplantation is considered the curative treatment option. The diversity of the DADA2 spectrum often delays diagnosis and treatment of this vulnerable patient cohort. We therefore recommend early ADA2 enzyme activity measurement as a screening tool for patients and siblings at risk, and we expect early steroid-based remission induction will help avoid fatal outcomes.
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