BackgroundCommon variable immunodeficiency (CVID) is a primary antibody deficiency characterized by a decrease in antibody production and low or normal B cell numbers. To elucidate the clinical and immunological heterogeneity of this condition, we studied 13 patients diagnosed with CVID, examined the status of B-cell maturation in patients with CVID by analyzing IgD/CD27 expression, and we analyze the in vitro B cell differentiation to plasma cells.MethodsT, B and NK cell populations was analyzed by flow citometry, expression of CD27 marker was determined to define B cell subsets; we also assessed molecules important for B cell proliferation and differentiation, such as TNFRSF13B (TACI), inducible costimulator (ICOS), CD154, CD20, ICOSL and BAFFR. For B cell differentiation assays, total PBMCs were cultured with CpG alone, or with SAC Cowan, Pokweed and CpG; flow cytometric analysis of plasmablast generation was perfomed after 7 days of culture.ResultsReduced numbers of T and B cells was observed in CVID patients, this reduction was more prominent in adults than in children. One group of 8 patients showed a significant reduction in IgD+CD27+ memory B cells while 3 patients had similar percentage than the healthy control group. The IgD-CD27+ memory B cell population was low in 10 patients (<12%); while it was similar to the healthy control group in 2 of the patients. BAFFR expression in B cells was reduced in 4 patients. Finally, the differentiation to plasmablasts was reduced in patients, stimulation with CpG induced 18.5% of plasmablasts (SD = 12.5%) whereas it was 24% (SD = 8.3%) in healthy controls.ConclusionsThese results suggest that a combined defect in T and B cells may account for CVID, at least in some patients. On the other hand, the complete analysis of markers important for B proliferation and differentiation such as ICOS, CD40, CD154 and TACI can be a useful tool for understanding this heterogeneous disease. B cells from CVID patients fail to progress to IgD-CD27+ memory B cells and plasmablasts. Based on these facts, we hypothesize that one or more crucial signaling molecules is required to induce terminal differentiation into memory B cells, if defective, may cause CVID.

BackgroundX-linked agammaglobulinemia (XLA) is characterized by impaired B-cell differentiation caused by mutations in Bruton's tyrosine kinase (Btk) gen. Btk is expressed in myeloid cells and recent evidence support that it participates in Toll like receptor signaling, but results regarding its rol in XLA patients are contradictories.ObjectiveTo evaluate lipopolysaccharide (LPS)-induced pro-inflammatory cytokine response in peripheral blood mononuclear cells (PBMC) from XLA patients.MethodsThirteen patients with XLA were included in the study. PBMC LPS-induced TNF-α, IL-1β, IL-6, and IL-10 production was determined by ELISA and compared with that obtained from matched healthy controls. Cytokine production was correlated with the severity of the mutation, affected domain and clinical characteristics.ResultsIn response to LPS, PBMC from XLA patients produced significantly higher amounts of pro-inflammatory cytokines and IL-10 compared with controls and this production is not influenced by the neither severity of mutation or the affected domain. PBMC from patients with a history of more hospital admissions before diagnosis and patients with lower expression of Btk in monocytes produced higher levels of TNF-α and IL-1β, respectively. PBMC from patients with lower IgA levels showed a higher production of TNF-α and IL-1β. Less severe (punctual) mutations in Btk gene were associated with higher IgG levels at diagnosis.ConclusionsOur results demonstrated a predominantly inflammatory response in XLA patients after LPS stimuli and suggest a TLR signaling dysregulation in absence of Btk. This response may be influenced by environmental factors.

CVID is one of the most common primary immunodeficiency diseases and is a diagnosis of exclusion. CVID is characterized by hypogammaglobulinemia and recurrent bacterial infections. About two third of CVID subjects have an autoimmune condition. The etiology of about 80% of CVID remains unknown. Genetic linkage studies in such families have found distinct homozygous mutations in the gene encoding LRBA. Since then, all 11 LRBA deficient CVID subjects identified to date have autoimmune diseases, all patients, except one presented hypogammaglobulinemia. All mutations reported caused the loss or LRBA expression in PBMCs. In this work, we explore the frequency of LRBA deficiency in a cohort of 40 patients with clinical diagnosis of CVID diagnosis, most of which, consanguinity is unknown. Two patients with LRBA deficiency were identified in this cohort. All of the forty patients showed hypogammaglobulinemia. We also correlate the deficiency of LRBA with Freiburg classification from which patients with mutations in LRBA were from group Ia an Ib.