Mutational analysis of human BAFF receptor TNFRSF13C (BAFF-R) in patients with common variable immunodeficiency.
ABSTRACT BAFF receptor (BAFF-R/BR3/TNFRSF13C) is a recently identified molecule that specifically binds BLyS, a protein belonging to the tumor necrosis factor (TNF) family, and is involved in survival and maturation of B cells. Recent studies have demonstrated that mice defective in BAFF-R gene exhibit an altered profile of the B cell pool, a phenotype observed in BLyS knockout mice as well. These features suggest that mutations in this gene may result in humoral immunodeficiency. To test this hypothesis, we sequenced the BAFF-R gene in 48 patients with common variable immunodeficiency (CVID) along with 57 healthy controls. We have identified three novel variants present at the heterozygous state leading to amino acid substitutions, and have also confirmed the existence of a previously reported intronic variant. The hereby described novel variants were also present in healthy controls and in the healthy patients' parents. These variants do not affect the expression of BAFF-R neither at the mRNA nor at the protein level, suggesting that these variants represent novel polymorphic variants of the BAFF-R gene.
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ABSTRACT: Purpose B-cell survival and differentiation critically depend on the interaction of BAFF-R and TACI with their ligands, BAFF and APRIL. Mature B-cell defects lead to Common Variable Immunodeficiency (CVID), which is associated with elevated serum levels of BAFF and APRIL. Nevertheless, BAFF-R and TACI expression in CVID and their relationship with ligand availability remain poorly understood. Methods and Results We found that BAFF-R expression was dramatically reduced on B cells of CVID patients, relative to controls. BAFF-R levels inversely correlated with serum BAFF concentration both in CVID and healthy subjects. We also found that recombinant BAFF stimulation reduced BAFF-R expression on B cells without decreasing transcript levels. On the other hand, CVID subjects had increased TACI expression on B cells in direct association with serum BAFF but not APRIL levels. Moreover, splenomegaly was associated with higher TACI expression, suggesting that perturbations of TACI function may underlie lymphoproliferation in CVID. Conclusions Our results indicate that availability of BAFF determines BAFF-R and TACI expression on B cells, and that BAFF-R expression is controlled by BAFF binding. Identification of the factors governing BAFF-R and TACI is crucial to understanding CVID pathogenesis, and B-cell biology in general, as well as to explore their potential as therapeutic targets.Journal of Clinical Immunology 07/2014; 34(5). · 3.38 Impact Factor
Article: BAFF-R mutations in Good's syndrome.Clinical Immunology 04/2014; · 3.77 Impact Factor
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ABSTRACT: Introduction: The B-cell activating factor (BAFF) axis comprises two ligands (BAFF and APRIL) and three receptors (BCMA, TACI, BR3). BAFF is a vital B-cell survival factor and overexpression of BAFF in both mice and humans is associated with systemic lupus erythematosus (SLE). The anti-BAFF monoclonal antibody (mAb), belimumab, was recently approved by the US FDA for the treatment of adult SLE patients, and three additional BAFF antagonists (atacicept, blisibimod, tabalumab) are presently being evaluated in SLE Phase-III trials. Areas covered: The general biological properties of the individual elements of the BAFF/APRIL axis are reviewed, with emphasis placed on molecular interactions and the potential relevance of each individual element to SLE. Expert opinion: The success of belimumab, an agent which promotes only modest B-cell depletion, is contrasted with the failure of the anti-CD20 mAb rituximab, an agent which promotes profound B-cell depletion, and multiple arguments are offered to explain this apparent paradox. Real and perceived limitations to belimumab therapy are presented, and possibilities for other therapeutic agents that target specific elements of the BAFF/APRIL axis are discussed.Expert opinion on therapeutic targets 02/2014; · 3.72 Impact Factor