Purpose
To investigate the clinical and functional aspects of MST1 (
STK4
) deficiency in a profoundly CD4-lymphopenic kindred with a novel homozygous nonsense mutation in
STK4.
Although recent ...studies have described the cellular effects of murine Mst1 deficiency, the phenotype of MST1-deficient human lymphocytes has yet to be fully explored. Patient lymphocytes were therefore investigated in the context of current knowledge of murine Mst1 deficiency.
Methods
Genetic etiology was identified by whole exome sequencing of genomic DNA from two siblings, combined with linkage analysis in the wider family. MST1 protein expression was assessed by immunoblotting. The ability of patient lymphocytes to adhere to ICAM-1 under flow conditions was measured, and transwell assays were used to assess chemotaxis. Chemokine receptor expression was examined by flow cytometry and receptor signalling by immunoblotting.
Results
A homozygous nonsense mutation in
STK4
(c.442C > T, p.Arg148Stop) was found in the patients, leading to a lack of MST1 protein expression. Patient leukocytes exhibited deficient chemotaxis after stimulation with CXCL11, despite preserved expression of CXCR3. Patient lymphocytes were also unable to bind effectively to immobilised ICAM-1 under flow conditions, in keeping with a failure to develop high affinity binding.
Conclusion
The observed abnormalities of adhesion and migration imply a profound trafficking defect among human MST1-deficient lymphocytes. By analogy with murine Mst1 deficiency and other defects of leucocyte trafficking, this is likely to contribute to immunodeficiency by impairing key aspects of T-cell development and function such as positive selection in the thymus, thymic egress and immune synapse formation in the periphery.
Lateral compartmentalization of the plasma membrane into domains is a key feature of immune cell activation and subsequent immune effector functions. Here, we will review the high diversity of ...membrane domains, ranging from elementary lipid rafts, envisioned as dynamic and small domains (in the tens of nm), to relatively stable μm‐scale membrane domains, which form the immunologic synapse of T lymphocytes. We will discuss the relationship between these different types of plasma membrane domains and how raft lipid‐ and protein‐controlled interactions and cell biological processes cooperate to generate functional domains that mediate lymphocyte activity.
Abstract Deficiency of dedicator of cytokinesis 8 (DOCK8) is a newly described combined primary immunodeficiency disease. It was found to account for 15% of combined immune deficiency cases in the ...National Primary Immunodeficiency Disorders Registry in Kuwait, a country with high prevalence of consanguinity. We present the clinical, immunologic and molecular characteristics of 9 Kuwaiti patients with DOCK8 deficiency and discuss differences that distinguish DOCK8 deficiency from atopic dermatitis. Clinical immunologists in areas with high incidence of consanguinity should have a high index of suspicion of DOCK8 deficiency in children with recalcitrant eczema, recurrent non-cutaneous infections and lymphopenia.
Abstract
Background and Aims
Very early onset inflammatory bowel disease VEOIBD is characterized by intestinal inflammation affecting infants and children less than 6 years of age. To date, over 60 ...monogenic aetiologies of VEOIBD have been identified, many characterized by highly penetrant recessive or dominant variants in underlying immune and/or epithelial pathways. We sought to identify the genetic cause of VEOIBD in a subset of patients with a unique clinical presentation.
Methods
Whole exome sequencing was performed on five families with ten patients who presented with a similar constellation of symptoms including medically refractory infantile-onset IBD, bilateral sensorineural hearing loss and, in the majority, recurrent infections. Genetic aetiologies of VEOIBD were assessed and Sanger sequencing was performed to confirm novel genetic findings. Western analysis on peripheral blood mononuclear cells and functional studies with epithelial cell lines were employed.
Results
In each of the ten patients, we identified damaging heterozygous or biallelic variants in the Syntaxin-Binding Protein 3 gene STXBP3, a protein known to regulate intracellular vesicular trafficking in the syntaxin-binding protein family of molecules, but not associated to date with either VEOIBD or sensorineural hearing loss. These mutations interfere with either intron splicing or protein stability and lead to reduced STXBP3 protein expression. Knock-down of STXBP3 in CaCo2 cells resulted in defects in cell polarity.
Conclusion
Overall, we describe a novel genetic syndrome and identify a critical role for STXBP3 in VEOIBD, sensorineural hearing loss and immune dysregulation.
ICOS encodes the Inducible T-cell Co-Stimulator (ICOS). Deficiency of this receptor in humans causes a common variable immunodeficiency (CVID) characterised by an absence of class-switched memory B ...cells and hypogammaglobulinemia. Three pathogenic mutations in ICOS have been described to date in a total of 13 cases. Here we report a novel homozygous 10 base pair frameshift deletion in exon 2 discovered by whole exome sequencing of two siblings from a family of Pakistani origin. Both patients presented in early childhood with diarrhea, colitis and transaminitis and one showed defective handling of human herpesvirus 6. Activated patient CD3(+)CD4(+) T lymphocytes demonstrated a complete absence of ICOS expression and, consistent with previous reports, we detected a reduction in circulating T follicular helper cells. Findings in this kindred emphasise the phenotypic variability of ICOS deficiency and, in particular, the variably impaired antiviral immunity that is a poorly understood facet of this rare disorder.
Purpose
We aimed to achieve a retrospective molecular diagnosis by applying state-of-the-art genomic sequencing methods to past patients with T-B+NK+ severe combined immunodeficiency (SCID). We ...included identification of copy number variations (CNVs) by whole exome sequencing (WES) using the CNV calling method ExomeDepth to detect gene alterations for which routine Sanger sequencing analysis is not suitable, such as large heterozygous deletions.
Methods
Of a total of 12 undiagnosed patients with T-B+NK+ SCID, we analyzed eight probands by WES, using GATK to detect single nucleotide variants (SNVs) and small insertions and deletions (INDELs) and ExomeDepth to detect CNVs.
Results
We found heterozygous single- or multi-exon deletions in
IL7R
, a known disease gene for autosomal recessive T-B+NK+ SCID, in four families (seven patients). In three families (five patients), these deletions coexisted with a heterozygous splice site or nonsense mutation elsewhere in the same gene, consistent with compound heterozygosity. In our cohort, about a quarter of T-B+NK+ SCID patients (26%) had such compound heterozygous
IL7R
deletions.
Conclusions
We show that heterozygous
IL7R
exon deletions are common in T-B+NK+ SCID and are detectable by WES. They should be considered if Sanger sequencing fails to detect homozygous or compound heterozygous
IL7R
SNVs or INDELs.
Inborn errors of T cell development present a pediatric emergency in which timely curative therapy is informed by molecular diagnosis. In 11 affected patients across four consanguineous kindreds, we ...detected homozygosity for a single deleterious missense variant in the gene NudC domain-containing 3 (
)
Two infants had severe combined immunodeficiency with the complete absence of T and B cells (T
B
SCID), whereas nine showed classical features of Omenn syndrome (OS). Restricted antigen receptor gene usage by residual T lymphocytes suggested impaired V(D)J recombination. Patient cells showed reduced expression of NUDCD3 protein and diminished ability to support RAG-mediated recombination in vitro, which was associated with pathologic sequestration of RAG1 in the nucleoli. Although impaired V(D)J recombination in a mouse model bearing the homologous variant led to milder immunologic abnormalities, NUDCD3 is absolutely required for healthy T and B cell development in humans.
Inflammatory bowel disease constitutes a heterogeneous group of conditions, whose aetiology is only partly understood. The prevailing hypothesis on its pathogenesis is that IBD is the result of an ...inadequate immune response to the resident bacterial flora of the intestine. An autoimmune background, however, has been discussed since the 1950s. Lately, it has been shown that failures in interleukin-10 (IL-10) signalling due to IL-10- and IL-10 receptor (IL-10R) mutations result in IBD. Our study aimed at investigating the existence of inhibitory autoantibodies against IL-10 and IL-10R in IBD patients capable of down-modulating IL-10 signalling thereby mimicking IL-10 or IL-10R deficiency.
Thirteen IBD patients had IgG autoantibodies against IL-10, IL-10RA and/or IL-10RB, and three patients had IgA autoantibodies against IL-10. However, the absolute OD values of the serum antibodies measured by ELISA were low, there was overall no significant difference between patients and controls, and positive sera had no neutralizing activity.
No evidence for an involvement of autoantibodies against IL-10 or IL-10R in the pathogenesis of inflammatory bowel disease could be established.
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