Laboratory Diagnosis of Specific Antibody Deficiency to Pneumococcal Capsular Polysaccharide Antigens (Clinical Immunology‪)‬

Infections caused by Streptococcus pneumoniae are an important cause of mortality and morbidity, particularly among children and older adults and immunocompromised patients (1). Also of major concern is emerging resistance of S. pneumoniae to antibiotic drugs (2). Phagocytes, complement, and specific antibodies to the capsular polysaccharides (caps-PS) are important in the host defense against S. pneumoniae (3). Pneumococcal caps-PS are polymers composed of repeating units of 2 to 5 different saccharide moieties. It has long been known that anti-caps-PS antibodies provide protection against invasive pneumococcal infection (3). Reports have appeared of patients suffering from recurrent infections with encapsulated microorganisms with normal antibody concentrations, but also with a specific deficiency in the production of anti-caps-PS antibodies (4, 5). Wasserman et al. estimated that 5%-10% of children referred for evaluation of recurrent infection suffer from this syndrome (6). Javier et al. found this disorder in 23% of patients who underwent immunologic evaluation for recurrent infection (7).