Abstract
The effect of CRP on the antibody response to pneumococcal C-polysaccharide (CPS) in BALB/c mice was examined. Mice were immunized by i.v. injection of formalinized Streptococcus pneumoniae serotype 3 and the IgM response to CPS measured as splenic plaqueforming cells (PFC) and serum hemagglutinating antibody. Administration of 200μg of CRP per mouse i.v. 30min prior to immunization reduced the peak PFC response on day 4 by more than 90%. Serum antibody and splenic PFC were measured on days 1 through 10, and inhibition was observed throughout the response. CRP was inhibitory at a minimum dose of 50μg per mouse, and 200μg CRP decreased the number of PFC by 50% when injected 6 hours after antigen. To determine whether the effect of CPS was related altered processing of particulate antigen, mice were immunized with horse erythrocytes (HE) coated with CPS or phosphocholine (PC) and the PFC response to CPS, PC and HE determined. CRP treatment inhibited the PFC response to CPS and PC without affecting the response to HE.
These results indicate that CRP may prevent immunization by masking determinants on bacterial or other surfaces.
