Project description:Trichothiodystrophy-1 (TTD1) is an autosomal-recessive disease and caused by mutations in ERCC2, a gene coding for a subunit of the TFIIH transcription and nucleotide-excision repair (NER) factor. In almost half of these patients infectious susceptibility has been reported but the underlying molecular mechanism leading to immunodeficiency is largely unknown. The aim of this study was to perform extended molecular and immunological phenotyping in patients suffering from TTD1. Cellular immune phenotype was investigated using multicolour flow cytometry. DNA repair efficiency was evaluated in UV-irradiation assays. Furthermore, early BCR activation events and proliferation of TTD1 lymphocytes following DNA damage induction was tested. In addition, we performed differential gene expression analysis in peripheral lymphocytes of TTD1 patients. We investigated three unrelated TTD1 patients who presented with recurrent infections early in life of whom two harboured novel ERCC2 mutations and the third patient is a carrier of previously described pathogenic ERCC2 mutations. Hypogammaglobulinemia and decreased antibody responses following vaccination were found. TTD1 B-cells showed accumulation of g-H2AX levels, decreased proliferation activity and reduced cell viability following UV-irradiation. mRNA sequencing analysis revealed significantly downregulated genes needed for B-cell development and activation. Analysis of B-cell subpopulations showed low numbers of naïve and transitional B-cells in TTD1 patients, indicating abnormal B-cell differentiation in vivo. In summary, our analyses confirmed the pathogenicity of novel ERCC2 mutations and show that ERCC2 deficiency is associated with antibody deficiency most likely due to altered B-cell differentiation resulting from impaired B-cell activation and activation-induced gene transcription.
Project description:Interaction of ICOS - ICOS ligand is required for the germinal center formation, T-cell immune responses, and development of autoimmune diseases. Human ICOS deficiency with the identical ICOS mutation has been identified in nine patients worldwide. In vitro studies showed T-cell defect of the patients was mild, and in vivo autoimmunity was uncommon and mild. Here we report in-depth analysis of T-cell function in two siblings with novel ICOS deficiency. While the brother displayed mild skin infections, psoriasis-like skin region, and defective immunoglobulin class switching, the sister had more severe symptoms, which included immunodeficiency, rheumatoid arthritis, inflammatory bowel disease, interstitial pneumonitis, and psoriasis. Despite of normal CD3/CD28-induced proliferation and IL-2 production in vitro, peripheral blood T-cells from both patients demonstrated decreased percentage of CD4 central and effector memory T-cells and impaired production of Th1, Th2, and Th17 cytokines upon CD3/CD28 costimulation or upon PMA/ionophore stimulation. The defective polarization into effector cells were associated with impaired induction of T-bet, GATA3 and MAF and RORC. Reduced CTLA-4+CD45RO+ FoxP3+ regulatory T-cells and diminished induction of inhibitory cell surface molecules including CTLA-4 were also observed in the patients. Further analysis of the gene expression and immune functions of the patients demonstrated increased induction of RANKL, lack of IFN-g response, and loss of Itch expression upon activation in the female case with autoimmunity. Our study suggests extensive T-cell dysfunction and loss of balance between effector cells and regulatory cells in the ICOS-deficient patients may account for their immunodeficiency and/or autoimmune disorder.