Dysregulated miR-155 and miR-125b Are Related to Impaired B-cell Responses in Down Syndrome

Children with Down Syndrome (DS) suffer from immune deficiency with a severe reduction in switched memory B cells (MBCs) and poor response to vaccination. Chromosome 21 (HSA21) encodes two microRNAs (miRs), miR-125b, and miR-155, that regulate B-cell responses. We studied B- and T- cell subpopulations in tonsils of DS and age-matched healthy donors (HD) and found that the germinal center (GC) reaction was impaired in DS. GC size, numbers of GC B cells and Follicular Helper T cells (TFH) expressing BCL6 cells were severely reduced. The expression of miR-155 and miR-125b was increased in tonsillar memory B cells and miR-125b was also higher than expected in plasma cells (PCs). Activation-induced cytidine deaminase (AID) protein, a miR-155 target, was significantly reduced in MBCs of DS patients. Increased expression of miR-155 was also observed in vitro. MiR-155 was significantly overexpressed in PBMCs activated with CpG, whereas miR-125b was constitutively higher than normal. The increase of miR-155 and its functional consequences were blocked by antagomiRs in vitro. Our data show that the expression of HSA21-encoded miR-155 and miR-125b is altered in B cells of DS individuals both in vivo and in vitro. Because of HSA21-encoded miRs may play a role also in DS-associated dementia and leukemia, our study suggests that antagomiRs may represent pharmacological tools useful for the treatment of DS

Different role of secretory IgA in the pathogenesis of RAST-positive and RAST-negative atopic dermatitis.

Secretory-IgA (SIgA) concentrations were determined in whole saliva, unstimulated or stimulated by lemon juice, of thirty-eight children with atopic dermatitis, which comprised three adolescents, sixteen with IgE detected by RAST to one or more common allergen and twenty-two without specific IgE by RAST. There were thirty healthy controls matched for age and sex. The mean amount of total IgE was significantly greater in the RAST-positive than in the RAST-negative group. The mean SIgA concentration in unstimulated saliva of the RAST-positive atopic dermatitis group was less than that of the RAST-negative atopic dermatitis group and control groups, through the mean concentrations of SIgA of stimulated saliva were not significantly different in the three groups. It is suggested that the pathogenesis of atopic dermatitis may differ in children with or without specific-IgE antibodies; in those who were RAST-positive deficient exclusion of allergen by the intestinal barrier contributed to the pathogenesis, but not in those who were RAST-negative

A new immunoperoxidase assay for lolium perenne-specific IgE in serum based on the biotin/avidin system (BAS).

A new solid-phase immunoassay based on the biotin/avidin system (BAS) for measuring serum Lolium perenne (LP)-specific IgE antibody is described. LP-specific IgE was assayed by the BAS assay and RAST for comparison in the sera of thirty-two normal asymptomatic subjects RAST-negative for LP and of twenty-six subjects with hay fever and RAST-positive for LP. The specificity of the BAS assay for LP-specific IgE was demonstrated by absorption experiments. An overall agreement of 91% (53/58) was observed between the BAS and RAST and a high correlation (r = 0.87, P less than 0.001) was found between the LP-specific IgE determined by the two methods. The advantages of the BAS assay as compared to both the RAST and classical ELISA are discussed

Serum IgG levels and complement activity in hypogammaglobulinemic patients under substitution therapy.

Haemolytic activity of the classical and alternative pathways of complement as well as serum levels of C1q, Factor B, Factor H, C3, C4, C3d,g and IgG were determined in 15 hypogammaglobulinaemic patients on immunoglobulin replacement therapy. Alternative pathway activity (AP) and C1q were defective in the presence of low IgG levels and normalized on achievement of normal IgG levels; for both variables the correlation with serum IgG was highly significant. Classical pathway activity (CP), C3, C4 and Factor H serum levels were normal independently of IgG levels; Factor B and C3d, g serum levels were elevated in hypogammaglobulinaemic patients regardless of IgG levels. The present report supports the hypothesis that IgG serum levels influence complement function

Effect of in vitro treatment with reducing drugs on structure and function of human secretory immunoglobulin A.

Samples of unstimulated whole saliva from 15 healthy children with 0.5--6 mg/100 ml of secretory IgA and from 10 healthy adults with 4--18 mg/100 ml of secretory IgA were pooled and treated in vitro with dithiothreitol and alpha-mercaptopropionylglycine. The effect of these reducing drugs on the immunochemical properties of secretory IgA was evaluated. Dithiothreitol induced depolymerization of secretory IgA and splitting of the secretory piece from the IgA molecule; furthermore it strongly reduced the titer of secretory antibodies to Escherichia coli antigens. The drug alpha-mercaptopropionylglycine apparently did not affect either the polymeric structure of secretory IgA or the titer of secretory anti-E. coli antibodies; however it induced splitting of the secretory piece. On the whole it appers that drugs with reducing properties, currently employed for liquifying mucous secretions in clinical practice, should be carefully evaluated for possible depressive side-effects on local immunity

Comparison of the frequency of atopic diseases in children with severe and partial IgA deficiency.

Similar frequencies of atopic diseases and of elevated total serum IgE levels were observed in 40 children with serum IgA levels below 5 mg/dl and absence of salivary IgA (severe selective IgA deficiency, SIgAD) and in 40 children with serum IgA levels above 5 mg/dl but below -2 SD of age-normal mean values and presence of salivary IgA (partial SIgAD). These findings suggest that the absence of secretory IgA, which has been postulated to play a protective role by excluding allergens at the mucosal level, does not appear to play a crucial role in the pathogenesis of atopic diseases