Cytotoxicity and proinflammatory effects of titanium and zirconia particles.

BACKGROUND: To assess the effects of differently sized titanium (Ti) and zirconia (Zr) particles on (1) the metabolic activity of osteosarcoma-derived osteoblasts (SaOs-2) and human gingival fibroblasts (HGF) and (2) the cytokine expression of monocytes (THP-1) METHODS: Ti (60-80 nm and 100 nm) and Zr (2 µm and 75 µm) particles were incubated with SaOs-2, HGF, and THP-1 cells. At days 0, 2, 4, and 7 and 0, 1, 2, and 4 (THP-1), the mitochondrial activity was assessed and enzyme-linked immunosorbent assays were used to determine interleukin (IL)-1 beta and IL-6 concentrations of stimulated THP-1 at day 1. RESULTS: Ti60-80, Ti100, Zr2, and Zr75 particles were associated with gradual and significant within-group decreases in the viability of SaOs-2 and HGF cells. These effects were less pronounced in the Zr group. Similar to control cells, THP-1 did not reveal any significant increases in IL-1 beta and IL-6 concentrations. Viability of THP-1 was merely impaired in the presence of Ti100. CONCLUSIONS: Ti and Zr particles had a detrimental effect on the viability of SaOs-2 and HGF, but no proinflammatory effect on THP-1.

Genetic CD21 deficiency is associated with hypogammaglobulinemia.

BACKGROUND: Complement receptor 2 (CR2/CD21) is part of the B-cell coreceptor and expressed by mature B cells and follicular dendritic cells. CD21 is a receptor for C3d-opsonized immune complexes and enhances antigen-specific B-cell responses. OBJECTIVE: Genetic inactivation of the murine CR2 locus results in impaired humoral immune responses. Here we report the first case of a genetic CD21 deficiency in human subjects. METHODS: CD21 protein expression was analyzed by means of flow cytometry and Western blotting. CD21 transcripts were quantified by using real-time PCR. The CD21 gene was sequenced. Wild-type and mutant CD21 cDNA expression was studied after transfection of 293T cells. Binding of EBV-gp350 or C3d-containing immune complexes and induction of calcium flux in CD21-deficient B cells were analyzed by means of flow cytometry. Antibody responses to protein and polysaccharide vaccines were measured. RESULTS: A 28-year-old man presented with recurrent infections, reduced class-switched memory B cells, and hypogammaglobulinemia. CD21 receptor expression was undetectable. Binding of C3d-containing immune complexes and EBV-gp350 to B cells was severely reduced. Sequence analysis revealed a compound heterozygous deleterious mutation in the CD21 gene. Functional studies with anti-immunoglobulin- and C3d-containing immune complexes showed a complete loss of costimulatory activity of C3d in enhancing suboptimal B-cell receptor stimulation. Vaccination responses to protein antigens were normal, but the response to pneumococcal polysaccharide vaccination was moderately impaired. CONCLUSIONS: Genetic CD21 deficiency adds to the molecular defects observed in human subjects with hypogammaglobulinemia.

Relevance of biallelic versus monoallelic TNFRSF13B mutations in distinguishing disease-causing from risk-increasing TNFRSF13B variants in antibody deficiency syndromes.

TNFRSF13B encodes transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI), a B cell- specific tumor necrosis factor (TNF) receptor superfamily member. Both biallelic and monoallelic TNFRSF13B mutations were identified in patients with common variable immunodeficiency disorders. The genetic complexity and variable clinical presentation of TACI deficiency prompted us to evaluate the genetic, immunologic, and clinical condition in 50 individuals with TNFRSF13B alterations, following screening of 564 unrelated patients with hypogammaglobulinemia. We identified 13 new sequence variants. The most frequent TNFRSF13B variants (C104R and A181E; n=39; 6.9%) were also present in a heterozygous state in 2% of 675 controls. All patients with biallelic mutations had hypogammaglobulinemia and nearly all showed impaired binding to a proliferation-inducing ligand (APRIL). However, the majority (n=41; 82%) of the pa-tients carried monoallelic changes in TNFRSF13B. Presence of a heterozygous mutation was associated with antibody deficiency (P< .001, relative risk 3.6). Heterozygosity for the most common mutation, C104R, was associated with disease (P< .001, relative risk 4.2). Furthermore, heterozygosity for C104R was associated with low numbers of IgD(-)CD27(+) B cells (P= .019), benign lymphoproliferation (P< .001), and autoimmune complications (P= .001). These associations indicate that C104R heterozygosity increases the risk for common variable immunodeficiency disorders and influences clinical presentation.

Sequence analysis of BIRC4/XIAP in male patients with common variable immunodeficiency.

BACKGROUND: Common variable immunodeficiency (CVID) is the most common primary antibody deficiency syndrome in humans, but it remains a diagnosis of exclusion in most cases. Several genetically defined primary immunodeficiencies mimic CVID. Among them is the X-linked lymphoproliferative syndrome (XLP) which was shown to be caused by either mutations in the gene SH2D1a/SAP or, more recently, in the BIRC4/XIAP gene. METHODS: We therefore analyzed a cohort of 28 male CVID patients and 2 patients with an IgG subclass deficiency for the prevalence of mutations in BIRC4, encoding for XIAP by direct sequencing. RESULTS: All patients showed a wild-type sequence of BIRC4/XIAP. Two SNPs, rs5956583 (dbSNP126) located in exon 6 (P-->Q) and rs28382740 (dbSNP126) in the 3' untranslated region were observed at the same frequencies as reported in public databases. CONCLUSIONS: We found no patient with a defect in the coding sequence of BIRC4/XIAP in our cohort of 30 hypogammaglobulinemic patients. We therefore estimate that XLP caused by XIAP deficiency may be a very rare differential diagnosis in male patients with CVID.

Screening of functional and positional candidate genes in families with common variable immunodeficiency.

BACKGROUND: Common variable immunodeficiency (CVID) comprises a heterogeneous group of primary antibody deficiencies with complex clinical and immunological phenotypes. The recent discovery that some CVID patients show monogenic defects in the genes encoding ICOS, TACI or CD19 prompted us to investigate several functional candidate genes in individuals with CVID. RESULTS: The exonic, protein coding regions of the genes encoding: APRIL, BCMA, IL10, IL10Ralpha, IL10Rbeta, IL21, IL21R, and CCL18, were analyzed primarily in familial CVID cases, who showed evidence of genetic linkage to the respective candidate gene loci and CVID families with a recessive pattern of inheritance. Two novel SNPs were identified in exon 5 and exon 8 of the IL21R gene, which segregated with the disease phenotype in one CVID family. Eleven additional SNPs in the genes encoding BCMA, APRIL, IL10, IL10Ralpha, IL21 and IL21R were observed at similar frequencies as in healthy donors. CONCLUSION: We were unable to identify obvious disease causing mutations in the protein coding regions of the analyzed genes in the studied cohort.