Defective pneumococcal antibody response in patients with recurrent respiratory tract infections.

Streptococcus pneumoniae is a common pathogen responsible for pulmonary infections and the leading cause of mortality and morbidity in patients with particularly B cell immunodeficiencies. Antibody production is the principal protective immune response against S. pneumoniae and measurement of the production of antipolysaccharide antibodies is important in the evaluation of B cell deficiencies. We quantified serotype-specific immunoglobulin G antibodies against seven common pneumococcal serotypes before and three weeks after unconjugated vaccine in 416 patients with recurrent respiratory tract infections; fifty-five (13%) of whom showed impaired antibody response. We could evaluate 41 of these 55 patients for their particular clinical features. Specific antibody deficiency, was diagnosed in 10 of these patients, common variable immunodeficiency in 18, ataxia telangiectasia in 10 and other antibody deficiencies in 7 (transient hypogammaglobulinemia in 4, IgG subclass deficiency in 1, partial and selective IgA deficiency in 1) patients. Evaluation of the antibody response to polysaccharide antigens should be considered early on in patients with recurrent respiratory infections and required particularly for the diagnosis of specific antibody deficiency and the decision of the appropriate treatment approaches.