Chapter 17 - Specific Antibody Deficiency with Normal Immunoglobulins

Abstract

Specific antibody deficiency (SAD) is a common antibody immunodeficiency defined as a poor antibody response to unconjugated pneumococcal polysccharides present in the 23-valent pneumococcal vaccine (PPV23). All immunoglobulin concentrations, including IgG subclasses, are normal, and antibody responses to protein antigens (e.g., tetanus toxoid, diphtheria toxoid) are also normal in most patients. In some patients with SAD, the response to the pneumococcal conjugate vaccines is also normal. The clinical manifestations of specific antibody deficiency include recurrent otitis media; sinopulmonary infections such as sinusitis; bronchitis; and pneumonia. In SAD patients these infections are more frequent or severe than infections observed in normal children or adults. There is not a single pathogenic mechanism for specific anti-polysaccharide antibody deficiencies. The variable conditions in which an inability to respond to polysaccharides is found suggest that many different immunologic phenotypes may lead to the same clinical phenotypic antibody deficiency. The interpretation of anti-pneumococcal antibody concentration results is based on increased post-immunization antibody concentrations over pre-immunization concentrations (immune response) and on the final post-immunization antibody concentrations, regardless of increase from pre-immunization concentrations (antibody concentration).