Defective anti-polysaccharide antibody response in patients with ataxia-telangiectasia.

The immunodeficiency in ataxia-telangiectasia (A-T) patients involves both cellular and humoral immunity; however, the specific antibody response is not well defined. Frequent respiratory infections are a prominent feature in A-T. Streptococcus pneumoniae is a common pathogen responsible for these infections. Defective B cell membrane signaling has been reported in A-T cells. These observations prompted us to investigate the B cell response to six frequently encountered pneumococcal serotypes in A-T patients. We found defective IgG antibody production to all studied serotypes (3, 6B, 7F, 14, 19F, and 23F) in 22 of 31 A-T patients (71%) who were immunized with a polyvalent pneumococcal vaccine. The impaired antibody responses did not correlate with either history of infection or serum immunoglobulin isotype levels. In addition, we did not observe any correlation between the pneumococcal antibody production and a specific mutation or level of intracellular ATM (ataxia-telangiectasia mutated) protein in lysates of lymphoblastoid cell lines from these patients. Our results suggest that the extent and severity of the recurrent sinopulmonary infections may depend not only on the immunological defects but also on other ATM-dependent physiological responses.

The effect of mannose-binding protein gene polymorphisms in recurrent respiratory system infections in children and lung tuberculosis.

Mannose-binding lectin (MBL) is able to bind pathogens as an opsonin and plays an important role in the innate immunity. The aim of the present study was to determine the frequencies of the MBL gene variants in the Turkish population and to examine the presence of any association between MBL variants and development of tuberculosis (TB) in adults and recurrent respiratory tract infections in children. Two structural gene mutations in exon 1 of MBL gene (codon 54 and codon 57) were studied. The overall distribution of genotypes did not significantly differ between controls and TB patients/children with recurrent respiratory system infections. The frequency of allele B was calculated as 0.14, 0.09 and 0.06 for control, TB patients and children with recurrent respiratory system infections, respectively. It was found to be significantly lower in children with recurrent respiratory system infections than in controls (chi2: 4.68, d.f: 1, p: 0.030).