Frequency of Treg cells is reduced in CVID patients with autoimmunity and splenomegaly and is associated with expanded CD21lo B lymphocytes

Increased serum IgM, immunodeficiency, and autoimmunity: A clinical series

BACKGROUND

Primary immunodeficiencies (PIDs) are generally characterized by recurrent infections; however they may be complicated by other clinical disorders such as allergy, autoimmunity, and lymphoproliferation. In particular, autoimmunity may be the first manifestation of the disease in patients with low serum immunoglobulins (Ig) levels. Here we describe a group of patients that share features of immunodeficiency and autoimmunity.

MATERIALS AND METHODS

All patients went through a complete T and B cell subset characterization and a B cell function analysis in the peripheral blood by flow-cytometry. B cell proliferation and plasma cell differentiation was measured, in vitro, after CpG stimulation for 7 days as previously described. Semi-quantitative PCR analysis for AID and UNG expression as well as serum levels of BAFF were carried out in order to better define the diagnosis.

RESULTS

Immunological and molecular analysis did not lead to the identification of known molecular defect typical of Hyper IgM syndrome. A comparative study of the peripheral blood B cell subsets between patients and healthy donors showed that in patients with autoimmune manifestations all circulating B cells expressed high amounts of surface IgM.

CONCLUSIONS

These results suggest that the increased IgM expression on circulating B cells, reflecting B cell activation, might identify a clinical condition characterized by hyper IgM serum levels of unknown molecular defects, associated with susceptibility to infections and autoimmunity.

Impaired CD8(+) T cell responses upon Toll-like receptor activation in common variable immunodeficiency

Background

Infections caused by bacteria or viruses are frequent in common variable immunodeficiency (CVID) patients due to antibody deficiencies, which may be associated with altered T cell function. CVID patients are frequently in contact with pathogen-associated molecular patterns (PAMPs), leading to the activation of innate immunity through Toll-like receptors (TLR) affecting T cell activation. We evaluated the effect of TLR activation on T cells in CVID patients undergoing intravenous immunoglobulin (IVIg) replacement using synthetic ligands.

Methods

Expression of exhaustion, activation and maturation markers on T cells from peripheral blood as well as regulatory T cells and follicular T cells in peripheral blood mononuclear cells (PBMCs) from CVID and healthy individuals were evaluated by flow cytometry. PBMCs cultured with TLR agonists were assessed for intracellular IFN-γ, TNF, IL-10, IL-17a or IL-22 secretion as monofunctional or polyfunctional T cells (simultaneous cytokine secretion) by flow cytometry.

Results

We found increased expression of the exhaustion marker PD-1 on effector memory CD4⁺ T cells (CD45RA⁻CCR7⁻) in the peripheral blood and increased expression of CD38 in terminally differentiated CD8⁺ T cells (CD45RA⁺CCR7⁻). Furthermore, a decreased frequency of naïve regulatory T cells (CD45RA⁺Foxp3^low), but not of activated regulatory T cells (CD45RA⁻Foxp3^high) was detected in CVID patients with splenomegaly, the non-infectious manifestation in this CVID cohort (43.7 %). Moreover, the frequency of peripheral blood follicular helper T cells (CD3⁺CD4⁺CXCR5⁺PD-1⁺ICOS⁺) was similar between the CVID and control groups. Upon in vitro TLR3 activation, a decreased frequency of CD8⁺ T cells secreting IFN-γ, IL-17a or IL-22 was detected in the CVID group compared to the control group. However, a TLR7/TLR8 agonist and staphylococcal enterotoxin B induced an increased Th22/Tc22 (IL-22⁺, IFN-γ⁻, IL-17a⁻) response in CVID patients. Both TLR2 and TLR7/8/CL097 activation induced an increased response of CD4⁺ T cells secreting three cytokines (IL-17a, IL-22 and TNF)in CVID patients, whereas CD8⁺ T cells were unresponsive to these stimuli.

Conclusion

The data show that despite the unresponsive profile of CD8⁺ T cells to TLR activation, CD4⁺ T cells and Tc22/Th22 cells are responsive, suggesting that activation of innate immunity by TLRs could be a strategy to stimulate CD4⁺ T cells in CVID.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0900-2) contains supplementary material, which is available to authorized users.

T-cell abnormalities in common variable immunodeficiency: the hidden defect

This review discusses how the T-cell compartment in common variable immunodeficiency is marked by the premature arrest in thymic output, leading to T-cell exhaustion and immune dysregulation. Although B cells have been the main focus of the disorder, ample experimental data suggest that T-cell abnormalities can be seen in a large proportion of Freiburg Group 1a patients and those suffering from inflammatory complications. The reductions in T-cell receptor excision circles, naïve T cells, invariant NKT cells and regulatory T cells suggest a diminished thymic output, while CD8 T cells are driven towards exhaustion either via an antigen-dependent or an antigen-independent manner. The theoretical risk of anti-T-cell therapies is discussed, highlighting the need for an international effort in generating longitudinal data in addition to better-defined underlying molecular characterisation.

Clinical Associations of Biallelic and Monoallelic TNFRSF13B Variants in Italian Primary Antibody Deficiency Syndromes

We assessed the prevalence of TNFRSF13B mutations and the clinical correlates in an Italian cohort of 189 CVID, 67 IgAD patients, and 330 healthy controls to substantiate the role of TACI genetic testing in diagnostic workup. We found that 11% of CVID and 13% of IgAD carried at least one mutated TNFRSF13B allele. Seven per cent of CVID had monoallelic-mutations and 4% had biallelic-mutations. The frequency of C104R monoallelic-mutations was not higher than that found in healthy controls. Biallelic-mutations were exclusively found in CVID. CVID patients carrying monoallelic-mutations had an increased prevalence of lymphadenopathy, granulomata, and autoimmune cytopenias. CVID carrying biallelic-mutations had a low prevalence of autoimmunity in comparison with TACI wild-type CVID. Moreover, biallelic-mutated CVID had higher frequency of switched memory B-cells and higher IgM and IgA antibodies to polysaccharide antigens than TACI wild-type and monoallelic-mutated CVID. TACI-mutated IgAD patients had only monoallelic-mutations and did not display clinical difference from IgAD wild-type patients. In conclusion, TNFRSF13B genetic screening of antibody deficiencies may allow the identification of mutational patterns. However, as with counseling for risk assessment, geneticists should be aware that the interpretation of genetic testing for TACI mutations is difficult and the potential impact on clinical management is still limited.

IL-10-Producing Regulatory B Cells Are Decreased in Patients with Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is the most prevalent symptomatic primary immunodeficiency in adults. CVID patients often present changes in the frequency and function of B lymphocytes, reduced number of Treg cells, chronic immune activation, recurrent infections, high incidence of autoimmunity and increased risk for malignancies. We hypothesized that the frequency of B10 cells would be diminished in CVID patients because these cells play an important role in the development of Treg cells and in the control of T cell activation and autoimmunity. Therefore, we evaluated the frequency of B10 cells in CVID patients and correlated it with different clinical and immunological characteristics of this disease. Forty-two CVID patients and 17 healthy controls were recruited for this study. Cryopreserved PBMCs were used for analysis of T cell activation, frequency of Treg cells and characterization of B10 cells by flow cytometry. IL-10 production by sorted B cells culture and plasma sCD14 were determined by ELISA. We found that CVID patients presented decreased frequency of IL-10-producing CD24^hiCD38^hi B cells in different cell culture conditions and decreased frequency of IL-10-producing CD24^hiCD27⁺ B cells stimulated with CpG+PIB. Moreover, we found that CVID patients presented lower secretion of IL-10 by sorting-purified B cells when compared to healthy controls. The frequency of B10 cells had no correlation with autoimmunity, immune activation and Treg cells in CVID patients. This work suggests that CVID patients have a compromised regulatory B cell compartment which is not correlated with clinical and immunological characteristics presented by these individuals.

Common variable immunodeficiency associated with microdeletion of chromosome 1q42.1-q42.3 and inositol 1,4,5-trisphosphate kinase B (ITPKB) deficiency

Common variable immunodeficiency (CVID) is a heterogenous disorder characterized by hypogammaglobulinemia and impaired specific antibody response and increased susceptibility to infections, autoimmunity and malignancies. A number of gene mutations, including ICOS, TACI and BAFF-R, and CD19, CD20, CD21, CD81, MSH5 and LRBA have been described; however, they account for approximately 20–25% of total cases of CVID. In this study, we report a patient with CVID with an intrinsic microdeletion of chromosome 1q42.1-42.3, where gene for inositol 1,3,4, trisphosphate kinase β (ITPKB) is localized. ITPKB has an important role in the development, survival and function of B cells. In this subject, the expression of ITPKB mRNA as well as ITKPB protein was significantly reduced. The sequencing of ITPKB gene revealed three variants, two of them were missense variants and third was a synonymous variant; the significance of each of them in relation to CVID is discussed. This case suggests that a deficiency of ITPKB may have a role in CVID.

CD4+CD25+Foxp3+ T regulatory cells, Th1 (CCR5, IL-2, IFN-γ) and Th2 (CCR4, IL-4, Il-13) type chemokine receptors and intracellular cytokines in children with common variable immunodeficiency

Common variable immunodeficiency (CVID) is a heterogeneous group of primary antibody deficiencies characterized by decreased serum immunoglobulin G along with a decrease in serum IgA and/or IgM, defective specific antibody production, and recurrent bacterial infections. Abnormal lymphocyte trafficking, dysregulated cellular responses to chemokines, and uncontrolled T cell polarization may be involved in the pathogenesis and may help to understand the clinical complications. We evaluated T helper cell subsets (chemokine receptors CCR4, CCR5, and CCR7), expressions on T lymphocytes, intracellular cytokines - IL-2, IL-4, IL-13, IFN- γ-on CD4(+) T cells, and expression of CD4(+)CD25(+)Foxp3(+) regulatory T cells of 20 CVID patients and 26 healthy controls. Autoimmune clinical findings and other complications were also determined. Percentages and absolute numbers of CD4(+)CD25(+) Foxp3(+) cells did not show any significant difference between CVID cases and healthy controls nor between severe and moderate disease patients. The only significant difference regarding Th1 and Th2 type intracellular cytokines was the decreased absolute numbers of CD3(+)CD4(+)IL4(+) cells in CVID cases. There were some findings about T helper cell type dominance in CVID patients such as positive correlation between hepatomegaly and high IL-2 and IFN-γ in CD3(+)CD4(+) cells and very high expression of CCR5 (Th1) on CD3(+)CD4(+) cells in patients with granuloma. Th1 (CCR5) and Th2 (CCR4) type chemokine receptors did not show any dominance in CVID cases. However, frequencies of CCR7 expressing CD3(+) T cells, CD3(+)CD4(+) T helper cells and CD3(+)CD8(+) T cytotoxic cells were significantly lower in severe CVID patients. In addition, presence of autoimmune clinical findings was negatively correlated with CCR7(+) cells. As CCR7 is a key mediator balancing immunity and tolerance in the immune system, the abnormality of this mediator may contribute to the profound immune dysregulation seen in CVID. In addition, Th1 cells seem to be more involved in the disease pathogenesis than Th2 cells.

TNF receptor superfamily member 13b (TNFRSF13B) hemizygosity reveals transmembrane activator and CAML interactor haploinsufficiency at later stages of B-cell development

BACKGROUND

Heterozygous C104R or A181E TNF receptor superfamily member 13b (TNFRSF13B) mutations impair removal of autoreactive B cells, weaken B-cell activation, and convey to patients with common variable immune deficiency (CVID) an increased risk for autoimmunity. How mutant transmembrane activator and CAML interactor (TACI) influences wild-type TACI function is unclear; different models suggest either a dominant negative effect or haploinsufficiency.

OBJECTIVE

We investigated potential TACI haploinsufficiency by analyzing patients with antibody-deficient Smith-Magenis syndrome (SMS) who possess only 1 TNFRSF13B allele and antibody-deficient patients carrying one c.204insA TNFRSF13B null mutation.

METHODS

We tested the reactivity of antibodies isolated from single B cells from patients with SMS and patients with a c.204insA TNFRSF13B mutation and compared them with counterparts from patients with CVID with heterozygous C104R or A181E TNFRSF13B missense mutations. We also assessed whether loss of a TNFRSF13B allele induced haploinsufficiency in naive and memory B cells and recapitulated abnormal immunologic features typical of patients with CVID with heterozygous TNFRSF13B missense mutations.

RESULTS

We found that loss of a TNFRSF13B allele does not affect TACI expression, activation responses, or establishment of central B-cell tolerance in naive B cells. Additionally, patients with SMS and those with a c.204insA TNFRSF13B mutation display normal regulatory T-cell function and peripheral B-cell tolerance. The lack of a TNFRSF13B allele did result in decreased TACI expression on memory B cells, resulting in impaired activation and antibody secretion.

CONCLUSION

TNFRSF13B hemizygosity does not recapitulate autoimmune features of CVID-associated C104R and A181E TNFRSF13B mutations, which likely encode dominant negative products, but instead reveals selective TACI haploinsufficiency at later stages of B-cell development.

Effect of TACI signaling on humoral immunity and autoimmune diseases

Transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI) is one of the receptors of B cell activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL). TACI is a regulator in the immune responses. TACI inhibits B cell expansion and promotes the differentiation and survival of plasma cells. The mechanisms underlying these effects probably involve changed expressions of some crucial molecules, such as B lymphocyte induced maturation protein-1 (Blimp-1) and inducible T-cell costimulator ligand (ICOSL) in B cells and/or plasma cells. However, abnormal TACI signaling may relate to autoimmune disorders. Common variable immune deficiency (CVID) patients with heterozygous mutations in TACI alleles increase susceptibility to autoimmune diseases. Taci^−/− mice and BAFF transgenic mice both develop signs of human SLE. These findings that indicate inappropriate levels of TACI signaling may disrupt immune system balance, thereby promoting the development of autoimmune diseases. In this review, we summarize the basic characteristics of the TACI ligands BAFF and APRIL, and detail the research findings on the role of TACI in humoral immunity. We also discuss the possible mechanisms underlying the susceptibility of CVID patients with TACI mutations to autoimmune diseases and the role of TACI in the pathogenesis of SLE.

Autoimmune and other cytopenias in primary immunodeficiencies: pathomechanisms, novel differential diagnoses, and treatment

Autoimmunity and immune dysregulation may lead to cytopenia and represent key features of many primary immunodeficiencies (PIDs). Especially when cytopenia is the initial symptom of a PID, the order and depth of diagnostic steps have to be performed in accordance with both an immunologic and a hematologic approach and will help exclude disorders such as systemic lupus erythematosus, common variable immunodeficiency, and autoimmune lymphoproliferative syndromes, hemophagocytic disorders, lymphoproliferative diseases, and novel differential diagnoses such as MonoMac syndrome (GATA2 deficiency), CD27 deficiency, lipopolysaccharide-responsive beige-like anchor (LRBA) deficiency, activated PI3KD syndrome (APDS), X-linked immunodeficiency with magnesium defect (MAGT1 deficiency), and others. Immunosuppressive treatment often needs to be initiated urgently, which impedes further relevant immunologic laboratory analyses aimed at defining the underlying PID. Awareness of potentially involved disease spectra ranging from hematologic to rheumatologic and immunologic disorders is crucial for identifying a certain proportion of PID phenotypes and genotypes among descriptive diagnoses such as autoimmune hemolytic anemia, chronic immune thrombocytopenia, Evans syndrome, severe aplastic anemia/refractory cytopenia, and others. A synopsis of pathomechanisms, novel differential diagnoses, and advances in treatment options for cytopenias in PID is provided to facilitate multidisciplinary management and to bridge different approaches.

The variable in common variable immunodeficiency: a disease of complex phenotypes

Common variable immunodeficiency (CVID) is the most common and clinically most important severe primary antibody deficiency and is characterized by low levels of IgG, IgA, and/or IgM, with a failure to produce specific antibodies. This diagnostic category represents a heterogeneous group of disorders, which present not only with acute and chronic infections but also with a range of inflammatory and autoimmune disorders as well as an increased incidence of lymphoma and other malignancies. Patients can now be categorized into distinct clinical phenotypes based on analysis of large cohort studies and be further stratified by immunologic laboratory testing. The biologic importance of this categorization is made clear by the 11-fold increase in mortality if even one of these phenotypes (cytopenias, lymphoproliferation, or enteropathy) is present. Limited progress in defining the underlying molecular causes has been made with known causative single gene defects accounting for only 3% of cases, and, for this and the reasons mentioned above, CVID remains resolute in its variability. This review provides a practical approach to risk stratification of these complex phenotypes by using current clinical categories and laboratory biomarkers. The effects of infection as well as inflammatory and autoimmune complications on different organ systems are discussed alongside strategies to reduce diagnostic delay. Recent developments in diagnostics and therapy are also explored.

CVID-associated TACI mutations affect autoreactive B cell selection and activation

Common variable immune deficiency (CVID) is an assorted group of primary diseases that clinically manifest with antibody deficiency, infection susceptibility, and autoimmunity. Heterozygous mutations in the gene encoding the tumor necrosis factor receptor superfamily member TACI are associated with CVID and autoimmune manifestations, whereas two mutated alleles prevent autoimmunity. To assess how the number of TACI mutations affects B cell activation and tolerance checkpoints, we analyzed healthy individuals and CVID patients carrying one or two TACI mutations. We found that TACI interacts with the cleaved, mature forms of TLR7 and TLR9 and plays an important role during B cell activation and the central removal of autoreactive B cells in healthy donors and CVID patients. However, only subjects with a single TACI mutation displayed a breached immune tolerance and secreted antinuclear antibodies (ANAs). These antibodies were associated with the presence of circulating B cell lymphoma 6-expressing T follicular helper (Tfh) cells, likely stimulating autoreactive B cells. Thus, TACI mutations may favor CVID by altering B cell activation with coincident impairment of central B cell tolerance, whereas residual B cell responsiveness in patients with one, but not two, TACI mutations enables autoimmune complications.

T cell phenotypes in patients with common variable immunodeficiency disorders: associations with clinical phenotypes in comparison with other groups with recurrent infections

Common variable immunodeficiency disorders (CVID) are a group of heterogeneous conditions that have in common primary failure of B cell function, although numerous T cell abnormalities have been described, including reduced proliferative response and reduced regulatory T cells. This study compared the T cell phenotype of CVID patients subdivided into clinical phenotypes as well as patients with partial antibody deficiencies [immunoglobulin (Ig)G subclass deficiency and selective IgA deficiency], X-linked agammaglobulinaemia (XLA) and healthy and disease controls. Absolute numbers of T cell subpopulations were measured by four-colour flow cytometry: naive T cells, central and effector memory and terminally differentiated (TEM) T cells, using CD45RA and CCR7 expression. Early, intermediate and late differentiation status of T cells was measured by CD27/CD28 expression. Putative follicular T cells, recent thymic emigrants and regulatory T cells were also assessed. Significant reduction in naive CD4 T cells, with reduced total CD4 and recent thymic emigrant numbers, was observed in CVID patients, most pronounced in those with autoimmune cytopenias or polyclonal lymphoproliferation. These findings suggest a lack of replenishment by new thymically derived cells. CD8 naive T cells were reduced in CVID patients, most significantly in the autoimmune cytopenia subgroup. There was a reduction in early differentiated CD4 and CD8 T cells and increased CD8 TEM in the CVID patients, particularly autoimmune cytopenia and polyclonal lymphoproliferation subgroups, suggesting a more activated T cell phenotype, due perhaps to an antigen-driven process. XLA patients had significantly reduced putative follicular T cells, which may depend on B cells for survival, while no significant alterations were observed in the T cells of those with IgG subclass deficiency or selective IgA deficiency.

Common variable immunodeficiency: crossroads between infections, inflammation and autoimmunity

Common variable immunodeficiency is a collection of diseases characterized by primary hypogammaglobulinemia. The causes of CVID are extremely heterogeneous and may affect virtually every pathway linked to B cell development and function. Clinical manifestations of CVID mainly include recurrent bacterial infections, but autoimmune, gastrointestinal, lymphoproliferative, granulomatous, and malignant disorders have also been frequently reported as associated conditions. We aimed to focus on the state of the art of the relationship between infections, inflammation and autoimmunity in CVID.

CVID patients with autoimmunity have elevated T cell expression of granzyme B and HLA-DR and reduced levels of Treg cells

AIMS

Common variable immunodeficiency (CVID) is a primary antibody immunodeficiency with approximately 20% of patients reporting additional autoimmune symptoms. The primary aim of this study was to compare the levels of activated and regulatory T cells (Treg cells) in CVID patients in an attempt to clarify their possible interactions leading to the generation of autoimmunity.

METHODS

Immunophenotyping of T cells was performed by flow cytometry using a whole blood approach. Surface expression of human leukocyte antigen HLA class II DR and intracellular levels of granzyme B in T cell subsets were assessed; Treg levels were measured using CD4 CD25, FOXp3 and CTLA-4.

RESULTS

CVID patients had higher levels of granzyme B and HLA-DR on CD8(+) T cells compared with control values (mean of 59% vs 30% and 45% vs 21%, respectively). Patients also had reduced levels of Treg cells compared with control values (con mean=3.24% vs pat=2.54%). Patients with autoimmunity (5/23) had a similar level of T cell activation markers to the rest of the patients but with lower Treg cells (mean of 1.1%) and reduced CD25 and CTLA-4 expression. Patients with autoimmunity had a higher ratio of activated to Treg cells compared with patients with no autoimmune symptoms.

CONCLUSIONS

These results highlight that reduced levels of Treg cells were associated with elevated levels of activated T cells, suggesting that reduced Treg cells in these patients may have functional consequences in allowing exaggerated T cell responses.

Common variable immunodeficiency: an update

Common variable immunodeficiency (CVID) describes a heterogeneous subset of hypogammaglobulinemias of unknown etiology. Typically, patients present with recurrent bacterial infections of the respiratory and gastrointestinal tract. A significant proportion of CVID patients develops additional autoimmune, inflammatory or lymphoproliferative complications. CVID is the most frequent symptomatic primary immunodeficiency encountered in adults. Informative monogenetic defects have been found in single patients and families but in most cases the pathogenesis is still elusive. Numerous immunological studies have demonstrated phenotypic and functional abnormalities of T cells, B cells and antigen-presenting cells. A hallmark is the impaired memory B-cell formation that has been taken advantage of for classifying CVID patients. Clinical multi-center studies have demonstrated a correlation between immunological markers and clinical presentation. Long-term outcome is significantly influenced by delay of diagnosis and treatment and the presence of chronic inflammatory complications. While immunoglobulin replacement therapy plus antibiotics can control infections in most cases, patients with non-infectious inflammatory complications such as granulomatous inflammation, interstitial lung disease, inflammatory bowel disease, lymphoproliferation and developing malignancies still represent a therapeutic challenge. In this review we provide a systematic overview of the immunological, clinical, diagnostic and therapeutic aspects of CVID and highlight recent developments in these fields.

Autoimmune cytopenias in common variable immunodeficiency

Common variable immunodeficiency (CVID) is a humoral immunodeficiency whose primary diagnostic features include hypogammaglobulinemia involving two or more immunoglobulin isotypes and impaired functional antibody responses in the majority of patients. While increased susceptibility to respiratory and other infections is a common thread that binds a large cross-section of CVID patients, the presence of autoimmune complications in this immunologically and clinically heterogeneous disorder is recognized in up to two-thirds of patients. Among the autoimmune manifestations reported in CVID (20–50%; Chapel et al., 2008; Cunningham-Rundles, 2008), autoimmune cytopenias are by far the most common occurring variably in 4–20% (Michel et al., 2004; Chapel et al., 2008) of these patients who have some form of autoimmunity. Association of autoimmune cytopenias with granulomatous disease and splenomegaly has been reported. The spectrum of autoimmune cytopenias includes thrombocytopenia, anemia, and neutropenia. While it may seem paradoxical “prima facie” that autoimmunity is present in patients with primary immune deficiencies, in reality, it could be considered two sides of the same coin, each reflecting a different but inter-connected facet of immune dysregulation. The expansion of CD21 low B cells in CVID patients with autoimmune cytopenias and other autoimmune features has also been previously reported. It has been demonstrated that this unique subset of B cells is enriched for autoreactive germline antibodies. Further, a correlation has been observed between various B cell subsets, such as class-switched memory B cells and plasmablasts, and autoimmunity in CVID. This review attempts to explore the most recent concepts and highlights, along with treatment of autoimmune hematological manifestations of CVID.

Pathogenesis of autoimmunity in common variable immunodeficiency

Common variable immunodeficiency (CVID) presents in up to 25% of patients with autoimmune (AI) manifestations. Given the frequency and early onset in some patients with CVID, AI dysregulation seems to be an integral part of the immunodeficiency. Antibody-mediated AI cytopenias, most often affecting erythrocytes and platelets make up over 50% of these patients. This seems to be distinct from mainly cell-mediated organ-specific autoimmunity. Some patients present like patients with AI lymphoproliferative syndrome. Interestingly, in the majority of patients with AI cytopenias the immunological examination reveals a dysregulated B and T cell homeostasis. These phenotypic changes are associated with altered signaling through the antigen receptor which may well be a potential risk factor for disturbed immune tolerance as has been seen in STIM1 deficiency. In addition, elevated B cell-activating factor serum levels in CVID patients may contribute to survival of autoreactive B cells. Of all genetic defects associated with CVID certain alterations in TACI, CD19, and CD81 deficiency have most often been associated with AI manifestations. In conclusion, autoimmunity in CVID offers opportunities to gain insights into general mechanisms of human autoimmunity.

Proteomic analysis of sera from common variable immunodeficiency patients undergoing replacement intravenous immunoglobulin therapy

Common variable immunodeficiency is the most common form of symptomatic primary antibody failure in adults and children. Replacement immunoglobulin is the standard treatment of these patients. By using a differential proteomic approach based on 2D-DIGE, we examined serum samples from normal donors and from matched, naive, and immunoglobulin-treated patients. The results highlighted regulated expression of serum proteins in naive patients. Among the identified proteins, clusterin/ApoJ serum levels were lower in naive patients, compared to normal subjects. This finding was validated in a wider collection of samples from newly enrolled patients. The establishment of a cellular system, based on a human hepatocyte cell line HuH7, allowed to ascertain a potential role in the regulation of CLU gene expression by immunoglobulins.

Autoimmunity in common variable immunodeficiency: correlation with lymphocyte phenotype in the French DEFI study

Common variable immunodeficiency (CVID) is the most frequent clinically expressed primary immunodeficiency in adults and is characterized by primary defective immunoglobulin production. Besides recurrent infectious manifestations, up to 20% of CVID patients develop autoimmune complications. In this study, we took advantages of the French DEFI database to investigate possible correlations between peripheral lymphocyte subpopulations and autoimmune clinical expression in CVID adult patients. In order to analyse homogeneous populations of patients with precise clinical phenotypes, we first focused on patients with autoimmune cytopenia because they represent prototypic autoantibody mediated diseases. In a secondary analysis, we have tested our conclusions including all "autoimmune" CVID patients. We describe one of the largest European studies with 311 CVID patients, including 55 patients with autoimmune cytopenia and 61 patients with clinical or serologic autoimmune expression, excluding autoimmune cytopenia. We clarify previous reports and we confirm a very significant correlation between an increased proportion of CD21(low) B cells and CVID associated autoimmune cytopenia, but independently of the presence of other autoimmune disorders or of splenomegaly. Moreover, in CVID associated autoimmune cytopenia, T cells display an activated phenotype with an increase of HLA-DR and CD95 expression and a decrease in the naïve T cell numbers. Patients with other autoimmune manifestations do not harbour this "T and B cells phenotypic picture". In view of recent findings on CD21(low) B cells in CVID and RA, we suggest that both a restricted subset of B cells and a T cell help are required for a breakdown of B cell tolerance against membrane auto antigens in CVID.

Flow cytometry study of blood cell subtypes reflects autoimmune and inflammatory processes in autoimmune polyendocrine syndrome type I

Autoimmune polyendocrine syndrome type I (APS I) is a recessive disorder caused by mutations in the autoimmune regulator (AIRE) gene. AIRE is expressed in medullary epithelial cells where it activates transcription of organ-specific proteins in thymus, thereby regulating autoimmunity. Patients with APS I have, in addition to autoimmune manifestations in endocrine organs, also often ectodermal dystrophies and chronic mucocutaneous candidiasis. The aim of this study was to characterize immune cell subpopulations in patients with APS I and their close relatives. Extensive blood mononuclear cell immunophenotyping was carried out on 19 patients with APS I, 18 first grade relatives and corresponding sex- and age-matched healthy controls using flow cytometry. We found a significant relative reduction in T helper cells coexpressing CCR6 and CXCR3 in patients with APS I compared to controls (mean = 4.10% versus 5.94% respectively, P = 0.035). The pools of CD16(+) monocytes and regulatory T cells (Tregs) were also lower in patients compared with healthy individuals (mean = 15.75% versus 26.78%, P = 0.028 and mean = 4.12% versus 6.73%, P = 0.029, respectively). This is the first report describing reduced numbers of CCR6(+)CXCR3(+) T helper cells and CD16(+) monocytes in patients with APS I We further confirm previous findings of reduced numbers of Tregs in these patients.