T and B lymphocyte abnormalities in bone marrow biopsies of common variable immunodeficiency

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.

The many faces of common variable immunodeficiency

Common variable immunodeficiency (CVID) is a rare immune deficiency characterized by low levels of serum IgG, IgA, and/or IgM, with a loss of Ab production. The diagnosis is most commonly made in adults between the ages of 20 and 40 years, but both children and much older adults can be found to have this immune defect. The range of clinical manifestations is broad, including acute and chronic infections, inflammatory and autoimmune diseases, and an increased incidence of cancer and lymphoma. For all of these reasons, the disease phenotype is both heterogeneous and complex. In the past few years, data from large patient registries have revealed that both selected laboratory markers and clinical phenotyping may aid in separating groups of subjects into biologically relevant categories. CVID consists of 2 phenotypes, 1 in which infections are the characteristic and another in which impressive inflammatory and/or hematologic complications also develop, including lymphadenopathy, splenomegaly, autoimmune cytopenias, enteropathy, and/or and granulomatous disease. These phenotypes appear to be stable, are related to immunologic and inflammatory markers, and are predictive of outcomes. This review outlines current understanding about this syndrome based on studies of large cohorts, highlighting the evaluation and treatment of complications and, in particular, the autoimmune and inflammatory conditions that affect these patients.

The many faces of the clinical picture of common variable immune deficiency

PURPOSE OF REVIEW

To summarize the recent advancements in common variable immune deficiency (CVID), specifically CVID genetics, clinical discoveries and treatment implications.

RECENT FINDINGS

Large genomic studies have implicated new genes in the pathogenesis of CVID, and basic science studies have contributed to our knowledge of potential mechanisms. Cohort studies have further defined the immunologic parameters and clinical presentation of CVID, as well as the factors that contribute to morbidity and mortality in this disease. Immunoglobulin remains the mainstay of treatment, although there may be a role for immunosuppression and other therapies.

SUMMARY

CVID is a genotypically and phenotypically heterogeneous primary immune deficiency, the genetic and clinical characteristics of which are under active investigation. Further, discovery may yield important new treatment protocols that can continue to reduce the morbidity and mortality from this disease.

Common variable immune deficiency in children--clinical characteristics varies depending on defect in peripheral B cell maturation

Common variable immune deficiency (CVID) is a heterogeneous disease associated with ineffective production of antibodies. It is usually diagnosed in adulthood, but a variable proportion of children develop CVID. Early identification of patients with potentially worse prognosis may help to avoid serious complications. The goal of this study was to associate the clinical phenotype of patients with early onset CVID with peripheral B-cell maturation profile. Four color flow cytometry was used to define distribution of peripheral B-cell subsets in 49 children with early-onset CVID. All clinical data were extracted from medical records. A proportion of patients demonstrated diminishing with time total B-lymphocytes pool, beyond physiological age-related changes. Irrespective from duration of the follow-up period the B-cell maturation profile in individual patients remained unchanged. We identified six different aberrant peripheral B cell maturation profiles associated with different clinical characteristics. Patients with an early B-cell maturation block earlier required replacement therapy and were at significantly greater risk of enteropathy, granuloma formation, cytopenia, and lymphoproliferation. B-cell maturation inhibited at the natural effector stage was associated with higher risk of autoimmune manifestations other than autoimmune cytopenia. Prevalence of male patients was observed among patients with B-cell maturation inhibited at naïve B-cell stage. In conclusion, the diagnostic process in patients with suspected early-onset CVID shall include routine analysis of peripheral B-cell maturation to provide surrogate markers identifying patients at greater risk of developing certain complications.

TACI mutations and impaired B-cell function in subjects with CVID and healthy heterozygotes

BACKGROUND

Mutations in the gene coding for the transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI) are found in 8% to 10% of subjects with common variable immunodeficiency (CVID). Although heterozygous mutations may coincide with immunodeficiency in a few families, most mutation-bearing relatives are not hypogammaglobulinemic. Thus, the role of TACI mutations in producing the immune defect remains unclear.

OBJECTIVE

This study examined the expression and function of TACI mutations in healthy heterozygous relatives.

METHODS

We examined the surface and intracellular expression of TACI protein in EBV-transformed B cells of patients and relatives with mutations in 7 families, binding of a proliferation-inducing ligand, and secretion of IgG and IgA by ligand-activated B cells. We tested whether Toll-like receptor 9 agonists increased TACI expression and whether an agonistic anti-TACI antibody could induce activation-induced cytidine deaminase mRNA in those with mutations.

RESULTS

Intracellular and extracellular TACI expression was defective for B cells of all subjects with mutations, including subjects with CVID and relatives. Although Toll-like receptor 9 triggering normally up-regulates B-cell TACI expression, this was defective for all subjects with mutations. Triggering TACI by an agonistic antibody showed loss of activation-induced cytidine deaminase mRNA induction in all mutation-bearing B cells. However, ligand-induced IgG and IgA production was normal for healthy relatives but not for subjects with CVID.

CONCLUSION

Thus, B cells of relatives of subjects with CVID who have mutations in TACI but normal immune globulin levels still have detectable in vitro B-cell defects.

The many faces of common variable immunodeficiency

Common variable immunodeficiency (CVID) is a rare immune deficiency characterized by low levels of serum IgG, IgA, and/or IgM, with a loss of Ab production. The diagnosis is most commonly made in adults between the ages of 20 and 40 years, but both children and much older adults can be found to have this immune defect. The range of clinical manifestations is broad, including acute and chronic infections, inflammatory and autoimmune diseases, and an increased incidence of cancer and lymphoma. For all of these reasons, the disease phenotype is both heterogeneous and complex. In the past few years, data from large patient registries have revealed that both selected laboratory markers and clinical phenotyping may aid in separating groups of subjects into biologically relevant categories. CVID consists of 2 phenotypes, 1 in which infections are the characteristic and another in which impressive inflammatory and/or hematologic complications also develop, including lymphadenopathy, splenomegaly, autoimmune cytopenias, enteropathy, and/or and granulomatous disease. These phenotypes appear to be stable, are related to immunologic and inflammatory markers, and are predictive of outcomes. This review outlines current understanding about this syndrome based on studies of large cohorts, highlighting the evaluation and treatment of complications and, in particular, the autoimmune and inflammatory conditions that affect these patients.

Rationale of anti-CD19 immunotherapy: an option to target autoreactive plasma cells in autoimmunity

Anti-CD20 therapy using rituximab directly targeting B cells has been approved for treatment of non-Hodgkin lymphoma, rheumatoid arthritis and anti-neutrophil cytoplasmic antibody-associated vasculitides and has led to reappreciation of B-lineage cells for anti-rheumatic treatment strategies. Moreover, blocking B-cell activating factor with belimumab, a drug that is licensed for treatment of active, seropositive systemic lupus erythematosus (SLE), represents an alternative, indirect anti-B-cell approach interfering with proper B-cell development. While these approaches apparently have no substantial impact on antibody-secreting plasma cells, challenges to improve the treatment of difficult-to-treat patients with SLE remain. In this context, anti-CD19 antibodies have the promise to directly target autoantibody-secreting plasmablasts and plasma cells as well as early B-cell differentiation stages not covered by anti-CD20 therapy. Currently known distinct expression profiles of CD19 by human plasma cell subsets, experiences with anti-CD19 therapies in malignant conditions as well as the rationale of targeting autoreactive plasma cells in patients with SLE are discussed in this review.

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.

Regulation of mucosal IgA responses: lessons from primary immunodeficiencies

Adaptive co-evolution of mammals and bacteria has led to the establishment of complex commensal communities on mucosal surfaces. In spite of having available a wealth of immune-sensing and effector mechanisms capable of triggering inflammation in response to microbial intrusion, mucosal immune cells establish an intimate dialogue with microbes to generate a state of hyporesponsiveness against commensals and active readiness against pathogens. A key component of this homeostatic balance is IgA, a noninflammatory antibody isotype produced by mucosal B cells through class switching. This process involves activation of B cells by IgA-inducing signals originating from mucosal T cells, dendritic cells, and epithelial cells. Here, we review the mechanisms by which mucosal B cells undergo IgA diversification and production and discuss how the study of primary immunodeficiencies facilitates better understanding of mucosal IgA responses in humans.

Morbidity and mortality in common variable immune deficiency over 4 decades

The demographics, immunologic parameters, medical complications, and mortality statistics from 473 subjects with common variable immune deficiency followed over 4 decades in New York were analyzed. Median immunoglobulin levels were IgG, 246 mg/dL; IgA, 8 mg/dL; and IgM, 21 mg/dL; 22.6% had an IgG less than 100 mg/dL. Males were diagnosed earlier (median age, 30 years) than females (median age, 33.5 years; P = .004). Ninety-four percent of patients had a history of infections; 68% also had noninfectious complications: hematologic or organ-specific autoimmunity, 28.6%; chronic lung disease, 28.5%; bronchiectasis, 11.2%; gastrointestinal inflammatory disease, 15.4%; malabsorption, 5.9%; granulomatous disease, 9.7%; liver diseases and hepatitis, 9.1%; lymphoma, 8.2%; or other cancers, 7.0%. Females had higher baseline serum IgM (P = .009) and were more likely to develop lymphoma (P = .04); 19.6% of patients died, a significantly shorter survival than age- and sex-matched population controls (P < .0001). Reduced survival was associated with age at diagnosis, lower baseline IgG, higher IgM, and fewer peripheral B cells. The risk of death was 11 times higher for patients with noninfectious complications (hazard ratio = 10.95; P < .0001). Mortality was associated with lymphoma, any form of hepatitis, functional or structural lung impairment, and gastrointestinal disease with or without malabsorption, but not with bronchiectasis, autoimmunity, other cancers, granulomatous disease, or previous splenectomy.

TLR-mediated B cell defects and IFN-α in common variable immunodeficiency

Common variable immune deficiency (CVID) B cells have impaired responses to TLR7 and TLR9 agonists including poor cell proliferation, loss of cytokine production, and failure to produce IgG or IgA. We show that TLR7- or 9-activated B cells from CVID subjects with >0.5% peripheral isotype-switched CD27(+) B cells (group 2) have increased mature Cγ1 and Cγ2 heavy-chain mRNA transcripts compared to subjects who have <0.5% isotype-switched cells (group 1). While TLR-stimulated CVID plasmacytoid dendritic cells for all subjects had impaired IFN-α production, TLR7 or TLR9 stimulation in the presence IFN-α normalized isotype-switched CD27(+) B cells, enhanced activation-induced cytidine deaminase mRNA, and significantly improved IgG production only for group 2 subjects. IFN-α also upregulated TLR7 and TLR9 mRNA expression comparable to normal levels in B cells of group 2 subjects, indicating that the loss of IFN-α could be a significant component of the B-cell defect for these subjects.

B-cell replication history and somatic hypermutation status identify distinct pathophysiologic backgrounds in common variable immunodeficiency

Common variable immunodeficiency disorder (CVID) is the most prevalent form of primary idiopathic hypogammaglobulinemia. Identification of genetic defects in CVID is hampered by clinical and immunologic heterogeneity. By flow cytometric immunophenotyping and cell sorting of peripheral B-cell subsets of 37 CVID patients, we studied the B-cell compartment at the B-cell subset level using the κ-deleting recombination excision circle assay to determine the replication history and the Igκ-restriction enzyme hot-spot mutation assay to assess the somatic hypermutation status. Using this approach, 5 B-cell patterns were identified, which delineated groups with unique replication and somatic hypermutation characteristics. Each B-cell pattern reflected an immunologically homogenous patient group for which we proposed a different pathophysiology: (1) a B-cell production defect (n = 8, 18%), (2) an early peripheral B-cell maturation or survival defect (n = 4, 11%), (3) a B-cell activation and proliferation defect (n = 12, 32%), (4) a germinal center defect (n = 7, 19%), and (5) a postgerminal center defect (n = 6, 16%). The results of the present study provide for the first time insight into the underlying pathophysiologic background in 5 immunologically homogenous groups of CVID patients. Moreover, this study forms the basis for larger cohort studies with the defined homogenous patient groups and will facilitate the identification of underlying genetic defects in CVID.

"A rose is a rose is a rose," but CVID is Not CVID common variable immune deficiency (CVID), what do we know in 2011?

Common variable immune deficiency (CVID) is the commonest symptomatic primary immunodeficiency and represents a heterogenous collection of disorders resulting mostly in antibody deficiency and recurrent infections. However, autoimmunity, granulomatous inflammation and malignancy frequently occur as part of the syndrome. The etiology of the condition has been poorly understood although in recent years, significant progress has been made in elucidating genetic mechanisms that can result in a CVID phenotype. In parallel to this, advances in treatment of the condition have also resulted in improved survival and quality of life for patients. There still remains significant work to be done in improving our understanding of the disease. In addition, recognition of the condition remains poor with significant diagnostic delays and avoidable morbidity. In this article, we review CVID with a particular focus on the areas of improving diagnosis and classification, recent developments in understanding the underlying etiology and genetics; and current treatment and monitoring recommendations for patients.