Abstract
C-reactive protein (CRP) is an acute serum protein that binds to the cell wall C-polysacchride of Streptococcus pneumoniae (CPS). I have previously shown that CRP treatment of mice alters splenic and hepatic clearance of Streptococcus pneumoniae serotype 3 (Pn 3) and increases resistance to fatal pneumococcal infection. In this study, the effects of CRP on the antibody response to CPS were examined. Mice were immunized by i. v. injection of formalinized Pn 3, and the antibody response to CPS measured as serum hemagglutinating antibody. Administration of 200 μg of CRP per mouse i. v. 30 minutes prior to immunization reduced the antibody response to CPS. Inhibition was observed on Days 3 through 10.
CRP was inhibitory at a minimun dose of 50 μg per mouse. To determine whether the effects of CRP were related to altered processing of particulate antigen, mice were immunized with horse erythrocytes (HE) coated with CPS and the antibody response to CPS and HE determined. CRP treatment inhibited the antibody response to CPS without affecting the response to HE.
These results suggested that CRP binding to antigenic determinants on bacterial surfaces may prevent effective immunization by these determinants.
