Long-term follow up of families with pathogenic NFKB1 variants reveals incomplete penetrance and frequent inflammatory sequelae.

Nuclear factor κ light-chain enhancer of activated B cells (NF-κB) family of evolutionarily conserved transcription factors are involved in key cellular signaling pathways. Previously, hypogammaglobulinemia and common variable immunodeficiency (CVID)-like phenotypes have been associated with NFKB1 variants and loss-of-function NFKB1 variants have been reported as the most common monogenic cause for CVID among Europeans. Here, we describe a Finnish cohort of NFKB1 carriers consisting of 31 living subjects in six different families carrying five distinct heterozygous variants. In contrast to previous reports, the clinical penetrance was not complete even with advancing age and the prevalence of CVID/hypogammaglobulinemia was significantly lower, whereas (auto)inflammatory manifestations were more common (42% of the total cohort). At current stage of knowledge, routine genetic screening of asymptomatic individuals is not recommended, but counseling of potential adult carriers seems necessary.

Characterization of Expanded Gamma Delta T Cells from Atypical X-SCID Patient Reveals Preserved Function and IL2RG-Mediated Signaling.

Abnormally high γδ T cell numbers among individuals with atypical SCID have been reported but detailed immunophenotyping and functional characterization of these expanded γδ T cells are limited. We have previously reported atypical SCID phenotype caused by hypomorphic IL2RG (NM_000206.3) c.172C > T;p.(Pro58Ser) variant. Here, we have further investigated the index patient's abnormally large γδ T cell population in terms of function and phenotype by studying IL2RG cell surface expression, STAT tyrosine phosphorylation and blast formation in response to interleukin stimulation, immunophenotyping, TCRvγ sequencing, and target cell killing. In contrast to his âºß T cells, the patient's γδ T cells showed normal IL2RG cell surface expression and normal or enhanced IL2RG-mediated signaling. Vδ2 + population was proportionally increased with a preponderance of memory phenotypes and high overall tendency towards perforin expression. The patient's γδ T cells showed enhanced cytotoxicity towards A549 cancer cells. His TCRvγ repertoire was versatile but sequencing of IL2RG revealed a novel c.534C > A; p.(Phe178Leu) somatic missense variant restricted to γδ T cells. Over time this variant became predominant in γδ T cells, though initially present only in part of them. IL2RG-Pro58Ser/Phe178Leu variant showed higher cell surface expression compared to IL2RG-Pro58Ser variant in stable HEK293 cell lines, suggesting that somatic p.(Phe178Leu) variant may at least partially rescue the pathogenic effect of germline p.(Pro58Ser) variant. In conclusion, our report indicates that expansion of γδ T cells associated with atypical SCID needs further studying and cannot exclusively be deemed as a homeostatic response to low numbers of conventional T cells.

Novel Hemizygous IL2RG p.(Pro58Ser) Mutation Impairs IL-2 Receptor Complex Expression on Lymphocytes Causing X-Linked Combined Immunodeficiency.

Hypomorphic IL2RG mutations may lead to milder phenotypes than X-SCID, named variably as atypical X-SCID or X-CID. We report an 11-year-old boy with a novel c. 172C>T;p.(Pro58Ser) mutation in IL2RG, presenting with atypical X-SCID phenotype. We also review the growing number of hypomorphic IL2RG mutations causing atypical X-SCID. We studied the patient's clinical phenotype, B, T, NK, and dendritic cell phenotypes, IL2RG and CD25 cell surface expression, and IL-2 target gene expression, STAT tyrosine phosphorylation, PBMC proliferation, and blast formation in response to IL-2 stimulation, as well as protein-protein interactions of the mutated IL2RG by BioID proximity labeling. The patient suffered from recurrent upper and lower respiratory tract infections, bronchiectasis, and reactive arthritis. His total lymphocyte counts have remained normal despite skewed T and B cells subpopulations, with very low numbers of plasmacytoid dendritic cells. Surface expression of IL2RG was reduced on his lymphocytes. This led to impaired STAT tyrosine phosphorylation in response to IL-2 and IL-21, reduced expression of IL-2 target genes in patient CD4+ T cells, and reduced cell proliferation in response to IL-2 stimulation. BioID proximity labeling showed aberrant interactions between mutated IL2RG and ER/Golgi proteins causing mislocalization of the mutated IL2RG to the ER/Golgi interface. In conclusion, IL2RG p.(Pro58Ser) causes X-CID. Failure of IL2RG plasma membrane targeting may lead to atypical X-SCID. We further identified another carrier of this mutation from newborn SCID screening, lost to closer scrutiny.

The duodenal microbiota composition of adult celiac disease patients is associated with the clinical manifestation of the disease.

BACKGROUND: Celiac disease is classically manifested in the gastrointestinal (GI) tract but extraintestinal symptoms, such as dermatitis herpetiformis (DH), are also common. Besides several well-known shared genetic risk factors and an environmental trigger, gliadin, factors determining the clinical outcome of the disease are not known. In this study, the role of duodenal microbiota in the celiac disease outcome was studied by analyzing mucosa-associated microbiota in celiac disease patients with a variety of intestinal and extraintestinal symptoms. METHODS: Microbiota in duodenal biopsy samples obtained from 33 patients with celiac disease with GI, DH, anemia, or mixed symptoms, as well as screen-detected asymptomatic celiac disease and 18 control subjects were analyzed using PCR denaturing gradient gel electrophoresis and a subset of samples additionally by the 16S ribosomal RNA gene sequencing. RESULTS: The composition and diversity of mucosal microbiota was associated with the manifestation of celiac disease when analyzed using PCR denaturing gradient gel electrophoresis and the 16S ribosomal RNA gene sequencing. The patients with celiac disease with GI symptoms or anemia had lower microbial diversity than those with DH. Moreover, the patients with GI symptoms had different intestinal microbiota composition and structure, dominated by Proteobacteria, in comparison to those with DH or control subjects (patients with dyspepsia). The relatively similar intestinal microbiota composition in the control subjects and those with DH was characterized by the high abundance of Firmicutes. CONCLUSIONS: The two common outcomes of celiac disease, classical GI and extraintestinal manifestations, had marked differences on the diversity and composition of intestinal microbiota. This association suggested that intestinal microbiota may have a role in the manifestation of the disease.

Cytokine response of human mononuclear cells induced by intestinal Clostridium species.

Altered composition of intestinal microbiota has been associated with various immunological disorders such as inflammatory bowel disease. Although Clostridium species are major inhabitants of the intestinal tract, their interaction with the host immunological system is yet poorly characterized. In this study, cytokine responses of human monocytic cell line THP-1 and peripheral blood mononuclear cells (PBMC) to six type strains representing common intestinal clostridial species were determined. The strains induced diverse cytokine responses in both THP-1 cells and PBMC. Clostridium perfringens was the most potent inducer of both tumour necrosis factor alpha (TNF-alpha) and interleukin-10 (IL-10), as compared to Clostridium histolyticum, Clostridium clostridioforme, Clostridium leptum, Clostridium sporosphaeroides and Blautia coccoides. Interleukin-8 (IL-8) production in PBMC was most efficiently stimulated by C. sporosphaeroides. The same PBMC preparations that responded strongly to Escherichia coli lipopolysaccharide (LPS) also responded strongly to bacterial stimulation. This indicates that the level of responsiveness is an individual feature of mononuclear cell preparations, and that the overall cytokine response is composed by a combination of host factors and microbial structures affecting them. This work supports the idea that the composition of the intestinal clostridial population influences immune responses and is likely to play an important role in intestinal homeostasis.

Association between the ABO blood group and the human intestinal microbiota composition.

BACKGROUND: The mucus layer covering the human intestinal epithelium forms a dynamic surface for host-microbial interactions. In addition to the environmental factors affecting the intestinal equilibrium, such as diet, it is well established that the microbiota composition is individually driven, but the host factors determining the composition have remained unresolved. RESULTS: In this study, we show that ABO blood group is involved in differences in relative proportion and overall profiles of intestinal microbiota. Specifically, the microbiota from the individuals harbouring the B antigen (secretor B and AB) differed from the non-B antigen groups and also showed higher diversity of the Eubacterium rectale-Clostridium coccoides (EREC) and Clostridium leptum (CLEPT) -groups in comparison with other blood groups. CONCLUSIONS: Our novel finding indicates that the ABO blood group is one of the genetically determined host factors modulating the composition of the human intestinal microbiota, thus enabling new applications in the field of personalized nutrition and medicine.

CD200 positive human mesenchymal stem cells suppress TNF-alpha secretion from CD200 receptor positive macrophage-like cells.

Human mesenchymal stem cells (hMSCs) display immunosuppressive properties in vitro and the potential has also been transferred successfully to clinical trials for treatment of autoimmune diseases. OX-2 (CD200), a member of the immunoglobulin superfamily, is widely expressed in several tissues and has recently been found from hMSCs. The CD200 receptor (CD200R) occurs only in myeloid-lineage cells. The CD200-CD200R is involved in down-regulation of several immune cells, especially macrophages. The present study on 20 hMSC lines shows that the CD200 expression pattern varied from high (CD200Hi) to medium (CD200Me) and low (CD200Lo) in bone marrow-derived mesenchymal stem cell (BMMSC) lines, whereas umbilical cord blood derived mesenchymal stem cells (UCBMSCs) were constantly negative for CD200. The role of the CD200-CD200R axis in BMMSCs mediated immunosuppression was studied using THP-1 human macrophages. Interestingly, hMSCs showed greater inhibition of TNF-α secretion in co-cultures with IFN-γ primed THP-1 macrophages when compared to LPS activated cells. The ability of CD200Hi BMMSCs to suppress TNF-α secretion from IFN-γ stimulated THP-1 macrophages was significantly greater when compared to CD200Lo whereas UCBMSCs did not significantly reduce TNF-α secretion. The interference of CD200 binding to the CD200R by anti-CD200 antibody weakened the capability of BMMSCs to inhibit TNF-α secretion from IFN-γ activated THP-1 macrophages. This study clearly demonstrated that the efficiency of BMMSCs to suppress TNF-α secretion of THP-1 macrophages was dependent on the type of stimulus. Moreover, the CD200-CD200r axis could have a previously unidentified role in the BMMSC mediated immunosuppression.