Relationship between serum IgG2 concentrations and antibody responses to pneumococcal polysaccharides in children with chronic chest symptoms.

We measured IgG-class antibodies to 12 pneumococcal antigens pre- and post-immunization with polyvalent pneumococcal vaccine in 31 children who had experienced chronic chest symptoms. The purpose of the study was to determine the relation of IgG subclasses, especially IgG2, to the subjects' antibody responses to bacterial polysaccharide antigens, to see if measuring IgG subclasses would predict these responses. Twenty-nine children (90%) had low or low-normal levels of one or more IgG subclasses, including 20 out of 31 (65%) with low or low-normal levels of IgG2. Children studied had a relatively poor increase in levels of antibody to 10 of the 12 pneumococcal vaccine antigens investigated. Both pre- and post-immunization antibody levels were related to pre-immune serum concentrations of IgG2. Pre-immunization antibody levels were strongly related to post-immunization levels; when post-immunization antibody levels were adjusted for pre-immunization levels by partial correlation, the correlation between anticapsular antibody level post-immunization and IgG2 was no longer significant. Thus, in children with chronic chest symptoms, levels of antibody measured at a random interval after natural exposure to these bacterial polysaccharide antigens are related to levels of IgG2 subclass, but antibody increases after vaccination appear to be affected more by other factors.