Abstract
Human antibodies to bacterial polyaaccharides consist primarily of IgG and are largely restricted to the IgG2 subclass. We examined the ontogeny of the IgG subclass response to pneumococcal polysaccharide type 3 to determine if the poor response of infants to immunization with polysaccharide antigens is due to a diminished capacity to form this subclass of antibodies. Sera from 33 patients aged 2 months to 25 years who had previously been shown to respond to polyvalent pneumococcal polysaccharide vaccine with IgG antibodies (greater than twofold rise in post-immunization titer) were assayed by ELISA using monoclonal antibodies specific for IgG1, IgG2, IgG3, or IgG4. IgG1 antibodies to pneumococcal polysaccharide type 3 were uniformly low in all age groups. In contrast, IgG2 antibody activity was lowest in children less than the age of 2 years (170±20 ng/ml), but rose progressively in the age group 2-5 years (210±40 ng/ml), 5-10 years (330±30 ng/ml), and over the age of 10 (390±30 ng/ml) (differences significant at p<.0005 by ANOVA). Since the prevention of infection using a purified bacterial polysaccharide vaccine appears to depend on an adequate serum level of IgG2 antibody, the delay in the ontogeny of the IgG2 subclass explains the relative ineffectiveness of purified polysaccharide vaccines in children under the age of 2 years. Our findings are consistent with the hypothesis that purified bacterial capsular polysaccharide antigens preferentially activate IgG2-coramitted B cell clones at all ages.
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Schatz, D., Barrett, D. ONTOGENY OF THE SUBCLASS OF ANTIBODY TO PNEUMOCOCCAL POLYSACCHARIDE TYPE 3. Pediatr Res 21 (Suppl 4), 317 (1987). https://doi.org/10.1203/00006450-198704010-00900
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DOI: https://doi.org/10.1203/00006450-198704010-00900