Possible role of human herpesvirus 8 in the lymphoproliferative disorders in common variable immunodeficiency

The emerging concept of antigen-driven lymphomas: epidemiology and treatment implications

PURPOSE OF REVIEW

Dramatic increases in the incidence of lymphomas worldwide have stimulated considerable efforts to identify factors that contribute to the etiology of this heterogeneous group of malignancies. The treatment and, ultimately, the prevention of lymphoma depend on our understanding of the complex interaction of exogenous agents with the molecular milieu which initiates and sustains a lymphoid malignancy. This review discusses the current evidence for the role of foreign or self antigens in the initiation of lymphomagenesis.

RECENT FINDINGS

Recent data have demonstrated an increased risk of lymphoma among individuals with chronic inflammatory conditions, persistent infections or immunodeficient states. Common to these clinical conditions is antigenic stimulation leading to an inflammatory cascade of cellular and cytokine reactions that may tax the host immune response, provoke tissue injury and eventually result in lymphoid neoplasia.

SUMMARY

Efforts to detect and suppress chronic, antigen-driven inflammation have suggested that neoplastic progression may often be interrupted and controlled. Elucidation of the etiologic mechanisms critical to the survival of these malignancies would provide promising alternatives for the prevention and treatment of some lymphomas.

Common variable immunodeficiency: The power of co-stimulation

Common variable immunodeficiency (CVID) is the most frequent symptomatic primary immune deficiency in adults. CVID is characterized by the sequelae of an antibody deficiency syndrome: an impaired terminal B cell differentiation results in hypogammaglobulinemia and susceptibility to recurrent infections by encapsulated bacteria. The clinical course of CVID is complicated by a plethora of systemic immunopathology, including autoimmunity, lymphoproliferation, malignancy and sarcoid-like granulomas. Phenotypic and functional studies in CVID patients revealed multiple abnormalities within the innate and adaptive immune system. The recent description of monogenic defects in ICOS, TACI and CD19 focussed our interest to an impaired T cell-B cell collaboration within the germinal center and intrinsic B cell defects as possible explanations for the etiology of CVID.

Monogenetic defects in common variable immunodeficiency: what can we learn about terminal B cell differentiation?

PURPOSE OF REVIEW

In human primary immunodeficiencies, more than 100 different genetic defects have been described. For the most prevalent primary immunodeficiency requiring medical attention, however, termed common variable immunodeficiency, no genetic cause had been defined until recently. In this review we will summarize the current progress in the molecular genetics of common variable immunodeficiency and put them in context with other important developments in the field.

RECENT FINDINGS

In recent years the first three monogenetic defects in the inducible costimulator, transmembrane activator and CAML interactor (TACI), and CD19 were discovered in patients with common variable immunodeficiency revealing a multifaceted genetic background for this disease. As a concise phenotype cannot be assigned to each of these genetic defects, there is a need for further development of classification systems for common variable immunodeficiency and the search of epigenetic factors influencing the course of the disease. Subgroups of common variable immunodeficiency patients with low IgM memory B cells may suffer from an increased rate of infections. Human herpes virus type 8 infections were identified as a risk factor for the development of granulomatous disease complications.

SUMMARY

The pathogenesis of common variable immunodeficiency shows a convergence on impaired terminal B cell differentiation. Recently discovered genetic defects support this view. A combined effort of genetic analysis and standardized assessment of immunological and clinical phenotypes will be necessary to further unravel the conundrum of common variable immunodeficiency.

Common variable immunodeficiency. Old questions are getting clearer

Common variable immunodeficiency (CVID) is a heterogeneous entity characterized by an impaired ability to produce antibodies. The failure is localized in partially mature B lymphocytes, though T lymphocyte abnormalities are occasionally present. This deficiency affects antibody synthesis and class switch from IgD and IgM, to IgG and IgA. CVID is related to selective IgA deficiency, and both abnormalities may coincide in one same family, and evolve from one to another in the same patient. The symptoms generally manifest in adults, but can occur at any age, even in infancy. Recurrent bacterial infections or pneumonias are frequent, and may be complicated by gastrointestinal problems, granulomas, autoimmune disorders or malignancies. A defect in memory B cells seems to condition the clinical severity. Recently, several mutations in genes encoding for molecules (CD19, TACI, ICOS) involved in B cell survival and isotype switch have been identified in patients with CVID. Nevertheless, genetic abnormalities have been found in less than 25 % of cases with CVID; the underlying mechanism thus remains unknown in the majority of CVID patients, and research in this field must continue.

Tackling the heterogeneity of CVID

PURPOSE OF REVIEW

Common variable immunodeficiency is clinically the most relevant primary immunodeficiency of the adult. Its heterogeneity has hindered progress in the pathogenetic understanding of the majority of common variable immunodeficiency patients. This abstract summarizes recent aspects of the field and emphasizes the need for a commonly accepted approach to classify common variable immunodeficiency.

RECENT FINDINGS

In the last 2 years, the first genetic defects underlying common variable immunodeficiency, including ICOS, TACI, BAFF-R and CD19, have been identified. The analysis of dendritic cells demonstrated alterations in a majority of patients in addition to the disturbed T and B-cell function. Several changes of the adaptive immune system might be secondary to an underlying chronic inflammatory setting possibly due to a HHV8 infection in a subgroup of patients with granulomatous disease, autoimmune phenomena and T-cell dysfunction. The occurrence of granulomatous inflammation is associated with a worse prognosis compared with common variable immunodeficiency patients without granuloma.

SUMMARY

The pathogenesis of common variable immunodeficiency includes disturbances of the adaptive as well as innate immune system. Identified monogenic defects account for about 10% of cases, leaving the majority of defects undefined and certainly in part epigenetic. To combine the known aspects of the pathogenesis of common variable immunodeficiency to a conclusive picture, the clinical and immunologic phenotyping of patients needs to be standardized.