Antibody activity of IgG subclasses against pneumococcal polysaccharides after vaccination.

The isotypic pattern of antipneumococcal polysaccharide antibodies with respect to IgG subclasses differs in adults and children. Adults show almost exclusively IgG2 activity, whereas children exhibit both IgG1 and IgG2 activity. The IgG subclass pattern of the antibody response after pneumococcal vaccination was evaluated in nine healthy children 1 to 2 years of age, eight healthy children 5 to 6 years old, and eight healthy adults. The number of individuals responding increased with age, and the response was mainly of the IgG1 subclass. The implications of this finding are discussed.