Impaired IgG antibody production to pneumococcal polysaccharides in patients with ataxia-telangiectasia

Various factors seem to be etiologic in the susceptibility to sinopulmonary infections in ataxia-telangiectasia (A-T) patients, i.e., low serum and sa livary IgA, low serum IgG2, and even aspiration of saliva. S. pnenmoniae is a common pathogen responsible from pulmonary infections and impaired antib ody response to polysaccharide antigens is seen in patients with IgG2 and I gA deficiency as well as patients with CVID and WAS. We studied IgG-type an tibody production to six pneumococcal serotypes in 29 A-T patients by ELISA before and 3-4 weeks after pneumococcal vaccine. The response was consider ed positive when the antibody titer was >10 U/ml but weak when the titer wa s 10-20 U/ml. Twenty-two of 29 (76%) patients did not respond to any of the serotypes, 5 (17%) showed a positive response to one serotype, 1 (3.4%) to two serotypes, and 1 (3.3%) to four serotypes. With conversion to gravimet ric units (ng IgG/ml) and >1800 ng/ml (300 ng Ab N/ml) considered a positiv e response, 5 of 29 (17.2%) patients showed a positive response (300 ng ab N/ml) to two dr fewer serotypes. All patients tested produced IgG antibody to tetanus toroid. Sixteen of 27 (59.3%) patients had low IgG2 and four (14 .8%) had low IgG3 levels, while 18 (62.1%) of 29 patients had low serum IgA . No correlation was found either between serum Ig isotype levels and antip olysaccharide antibody response or between susceptibility to infection and antibody production. The mechanism responsible for disturbed antipolysaccha ride (TI-2 antigen) antibody production in patients with A-T needs to be in vestigated. It may provide additional information on the function of the AT M gene product and be helpful in clarifying the role of B cells and contrib ution of T cells in TI-2 responses.