IgG4-related disease and B-cell malignancy due to an IKZF1 gain-of-function variant.

BACKGROUND: Monoallelic loss-of-function IKZF1 (IKAROS) variants cause B-cell deficiency or combined immunodeficiency, whereas monoallelic gain-of-function (GOF) IKZF1 variants have recently been reported to cause hypergammaglobulinemia, abnormal plasma cell differentiation, autoimmune and allergic manifestations, and infections. OBJECTIVE: We studied 7 relatives with autoimmune/inflammatory and lymphoproliferative manifestations to identify the immunologic disturbances and the genetic cause of their disease. METHODS: We analyzed biopsy results and performed whole-exome sequencing and immunologic studies. RESULTS: Disease onset occurred at a mean age of 25.2 years (range, 10-64, years). Six patients suffered from autoimmune/inflammatory diseases, 4 had confirmed IG4-related disease (IgG4-RD), and 5 developed B-cell malignancies: lymphoma in 4 and multiple myeloma in the remaining patient. Patients without immunosuppression were not particularly prone to infectious diseases. Three patients suffered from life-threatening coronavirus disease 2019 pneumonia, of whom 1 had autoantibodies neutralizing IFN-α. The recently described IKZF1 GOF p.R183H variant was found in the 5 affected relatives tested and in a 6-year-old asymptomatic girl. Immunologic analysis revealed hypergammaglobulinemia and high frequencies of certain lymphocyte subsets (exhausted B cells, effector memory CD4 T cells, effector memory CD4 T cells that have regained surface expression of CD45RA and CD28-CD57+ CD4+ and CD8+ T cells, TH2, and Tfh2 cells) attesting to immune dysregulation. Partial clinical responses to rituximab and corticosteroids were observed, and treatment with lenalidomide, which promotes IKAROS degradation, was initiated in 3 patients. CONCLUSIONS: Heterozygosity for GOF IKZF1 variants underlies autoimmunity/inflammatory diseases, IgG4-RD, and B-cell malignancies, the onset of which may occur in adulthood. Clinical and immunologic data are similar to those for patients with unexplained IgG4-RD. Patients may therefore benefit from treatments inhibiting pathways displaying IKAROS-mediated overactivity.

Inherited human ezrin deficiency impairs adaptive immunity.

BACKGROUND: Inborn errors of immunity (IEI) are a group of monogenic diseases that confer susceptibility to infection, autoimmunity, and cancer. Despite the life-threatening consequences of some IEI, their genetic cause remains unknown in many patients. OBJECTIVE: We investigated a patient with an IEI of unknown genetic etiology. METHODS: Whole-exome sequencing identified a homozygous missense mutation of the gene encoding ezrin (EZR), substituting a threonine for an alanine at position 129. RESULTS: Ezrin is one of the subunits of the ezrin, radixin, and moesin (ERM) complex. The ERM complex links the plasma membrane to the cytoskeleton and is crucial for the assembly of an efficient immune response. The A129T mutation abolishes basal phosphorylation and decreases calcium signaling, leading to complete loss of function. Consistent with the pleiotropic function of ezrin in myriad immune cells, multidimensional immunophenotyping by mass and flow cytometry revealed that in addition to hypogammaglobulinemia, the patient had low frequencies of switched memory B cells, CD4+ and CD8+ T cells, MAIT, γδ T cells, and centralnaive CD4+ cells. CONCLUSIONS: Autosomal-recessive human ezrin deficiency is a newly recognized genetic cause of B-cell deficiency affecting cellular and humoral immunity.

Inherited Human BCL10 Deficiencies.

Human BCL10 deficiency causes combined immunodeficiency with bone marrow transplantation as its only curative option. To date, there are four homozygous mutations described in the literature that were identified in four unrelated patients. Here, we describe a fifth patient with a novel mutation and summarize what we have learned about BCL10 deficiency. Due to the severity of the disease, accurate knowledge of its clinical and immunological characteristics is instrumental for early diagnosis and adequate clinical management of the patients.

Novel PGM3 compound heterozygous variants with IgE-related dermatitis, lymphopenia, without syndromic features.

BACKGROUND: Phosphoglucomutase-3 (PGM3) deficiency is a congenital disorder of glycosylation (CDG) with hyperimmunoglobulin IgE, atopy, and a variable immunological phenotype; most reported patients display dysmorphic features. The aim of the study was to characterize the genotype and phenotype of individuals with newly identified compound heterozygous variants in the phosphate-binding domain of PGM3 in order to better understand phenotypic differences between these patients and published cases. METHODS: We analyzed PGM3 protein expression, PGM3 enzymatic activity, the presence of other gene variants within the N-glycosylation pathway, and the clinical and immunological manifestations of two affected siblings. RESULTS: Patients belonged to a non-consanguineous family, presenting with atopic dermatitis, elevated levels of IgE, and CD4+ lymphopenia (a more severe phenotype was observed in Patient 2), but lacked dysmorphic features or neurocognitive impairment. Compound heterozygous PGM3 variants were identified, located in the phosphate-binding domain of the enzyme. PGM3 expression was comparable to healthy donors, but L-PHA binding in naïve-CD4+ cells was decreased. Examination of exome sequence identified the presence of one additional candidate variant of unknown significance (VUS) in the N-glycosylation pathway in Patient 2: a variant predicted to have moderate-to-high impact in ALG12. CONCLUSIONS: Our analysis revealed that L-PHA binding is reduced in naïve-CD4+ cells, which is consistent with decreased residual PGM3 enzymatic activity. Other gene variants in the N-glycosylation pathway may modify patient phenotypes in PGM3 deficiency. This study expands the clinical criteria for when PGM3 deficiency should be considered among individuals with hyper-IgE.

Human BCL10 Deficiency due to Homozygosity for a Rare Allele.

In 2014, a child with broad combined immunodeficiency (CID) who was homozygous for a private BCL10 allele was reported to have complete inherited human BCL10 deficiency. In the present study, we report a new BCL10 mutation in another child with CID who was homozygous for a BCL10 variant (R88X), previously reported as a rare allele in heterozygosis (minor allele frequency, 0.000003986). The mutant allele was a loss-of-expression and loss-of-function allele. As with the previously reported patient, this patient had complete BCL10 deficiency. The clinical phenotype shared features, such as respiratory infections, but differed from that of the previous patient that he did not develop significant gastroenteritis episodes or chronic colitis. Cellular and immunological phenotypes were similar to those of the previous patient. TLR4, TLR2/6, and Dectin-1 responses were found to depend on BCL10 in fibroblasts, and final maturation of T cell and B cell maturation into memory cells was affected. Autosomal-recessive BCL10 deficiency should therefore be considered in children with CID.

Sustained interleukin-1ß exposure modulates multiple steps in glucocorticoid receptor signaling, promoting split-resistance to the transactivation of prominent anti-inflammatory genes by glucocorticoids.

Clinical treatment with glucocorticoids (GC) can be complicated by cytokine-induced glucocorticoid low-responsiveness (GC-resistance, GCR), a condition associated with a homogeneous reduction in the expression of GC-receptor- (GR-) driven anti-inflammatory genes. However, GR level and phosphorylation changes modify the expression of individual GR-responsive genes differently. As sustained IL-1ß exposure is key in the pathogenesis of several major diseases with prevalent GCR, we examined GR signaling and the mRNA expression of six GR-driven genes in cells cultured in IL-1ß and afterwards challenged with GC. After a GC challenge, sustained IL-1ß exposure reduced the cytoplasmic GR level, GR(Ser203) and GR(Ser211) phosphorylation, and GR nuclear translocation and led to selective GCR in the expression of the studied genes. Compared to GC alone, in a broad range of GC doses plus sustained IL-1ß, FKBP51 mRNA expression was reduced by 1/3, TTP by 2/3, and IRF8 was completely knocked down. In contrast, high GC doses did not change the expression of GILZ and DUSP1, while IGFBP1 was increased by 5-fold. These effects were cytokine-selective, IL-1ß dose- and IL-1R1-dependent. The integrated gain and loss of gene functions in the "split GCR" model may provide target cells with a survival advantage by conferring resistance to apoptosis, chemotherapy, and GC.

Ordering human CD34+CD10-CD19+ pre/pro-B-cell and CD19- common lymphoid progenitor stages in two pro-B-cell development pathways.

Studies here respond to two long-standing questions: Are human "pre/pro-B" CD34(+)CD10(-)CD19(+) and "common lymphoid progenitor (CLP)/early-B" CD34(+)CD10(+)CD19(-) alternate precursors to "pro-B" CD34(+)CD19(+)CD10(+) cells, and do the pro-B cells that arise from these progenitors belong to the same or distinct B-cell development pathways? Using flow cytometry, gene expression profiling, and Ig V(H)-D-J(H) sequencing, we monitor the initial 10 generations of development of sorted cord blood CD34(high)Lineage(-) pluripotential progenitors growing in bone marrow S17 stroma cocultures. We show that (i) multipotent progenitors (CD34(+)CD45RA(+)CD10(-)CD19(-)) directly generate an initial wave of Pax5(+)TdT(-) "unilineage" pre/pro-B cells and a later wave of "multilineage" CLP/early-B cells and (ii) the cells generated in these successive stages act as precursors for distinct pro-B cells through two independent layered pathways. Studies by others have tracked the origin of B-lineage leukemias in elderly mice to the mouse B-1a pre/pro-B lineage, which lacks the TdT activity that diversifies the V(H)-D-J(H) Ig heavy chain joints found in the early-B or B-2 lineage. Here, we show a similar divergence in human B-cell development pathways between the Pax5(+)TdT(-) pre/pro-B differentiation pathway that gives rise to infant B-lineage leukemias and the early-B pathway.

Case Report: Novel STIM1 Gain-of-Function Mutation in a Patient With TAM/STRMK and Immunological Involvement.

Gain-of-function (GOF) mutations in STIM1 are responsible for tubular aggregate myopathy and Stormorken syndrome (TAM/STRMK), a clinically overlapping multisystemic disease characterised by muscle weakness, miosis, thrombocytopaenia, hyposplenism, ichthyosis, dyslexia, and short stature. Several mutations have been reported as responsible for the disease. Herein, we describe a patient with TAM/STRMK due to a novel L303P STIM1 mutation, who not only presented clinical manifestations characteristic of TAM/STRMK but also manifested immunological involvement with respiratory infections since childhood, with chronic cough and chronic bronchiectasis. Despite the seemingly normal main immunological parameters, immune cells revealed GOF in calcium signalling compared with healthy donors. The calcium flux dysregulation in the immune cells could be responsible for our patient's immune involvement. The patient's mother carried the mutation but did not exhibit TAM/STRMK, manifesting an incomplete penetrance of the mutation. More cases and evidence are necessary to clarify the dual role of STIM1 in immune system dysregulation and myopathy.

Role of CD39 in COVID-19 Severity: Dysregulation of Purinergic Signaling and Thromboinflammation.

CD39/NTPDase1 has emerged as an important molecule that contributes to maintain inflammatory and coagulatory homeostasis. Various studies have hypothesized the possible role of CD39 in COVID-19 pathophysiology since no confirmatory data shed light in this regard. Therefore, we aimed to quantify CD39 expression on COVID-19 patients exploring its association with severity clinical parameters and ICU admission, while unraveling the role of purinergic signaling on thromboinflammation in COVID-19 patients. We selected a prospective cohort of patients hospitalized due to severe COVID-19 pneumonia (n=75), a historical cohort of Influenza A pneumonia patients (n=18) and sex/age-matched healthy controls (n=30). CD39 was overexpressed in COVID-19 patients' plasma and immune cell subsets and related to hypoxemia. Plasma soluble form of CD39 (sCD39) was related to length of hospital stay and independently associated with intensive care unit admission (adjusted odds ratio 1.04, 95%CI 1.0-1.08, p=0.038), with a net reclassification index of 0.229 (0.118-0.287; p=0.036). COVID-19 patients showed extracellular accumulation of adenosine nucleotides (ATP and ADP), resulting in systemic inflammation and pro-coagulant state, as a consequence of purinergic pathway dysregulation. Interestingly, we found that COVID-19 plasma caused platelet activation, which was successfully blocked by the P2Y12 receptor inhibitor, ticagrelor. Therefore, sCD39 is suggested as a promising biomarker for COVID-19 severity. As a conclusion, our study indicates that CD39 overexpression in COVID-19 patients could be indicating purinergic signaling dysregulation, which might be at the basis of COVID-19 thromboinflammation disorder.

Clinical and Immunological Features of Human BCL10 Deficiency.

The CARD-BCL10-MALT1 (CBM) complex is critical for the proper assembly of human immune responses. The clinical and immunological consequences of deficiencies in some of its components such as CARD9, CARD11, and MALT1 have been elucidated in detail. However, the scarcity of BCL10 deficient patients has prevented gaining detailed knowledge about this genetic disease. Only two patients with BCL10 deficiency have been reported to date. Here we provide an in-depth description of an additional patient with autosomal recessive complete BCL10 deficiency caused by a nonsense mutation that leads to a loss of expression (K63X). Using mass cytometry coupled with unsupervised clustering and machine learning computational methods, we obtained a thorough characterization of the consequences of BCL10 deficiency in different populations of leukocytes. We showed that in addition to the near absence of memory B and T cells previously reported, this patient displays a reduction in NK, γδT, Tregs, and TFH cells. The patient had recurrent respiratory infections since early childhood, and showed a family history of lethal severe infectious diseases. Fortunately, hematopoietic stem-cell transplantation (HSCT) cured her. Overall, this report highlights the importance of early genetic diagnosis for the management of BCL10 deficient patients and HSCT as the recommended treatment to cure this disease.