The use of radioactively labeled S III to study the blood clearance and the immune response of mice to pneumococcal polysaccharides

Abstract Methods are described for the preparation of radioactively labeled type III pneumococcal polysaccharide. Using this radioactive antigen the Farr technique was adapted for the accurate and simple measurement of nanogram amounts of either antipneumococcal polysaccharide antibodies or pneumococcal polysaccharide (S III). By use of these reagents and methods the clearance of S III from the circulation of mice was followed and the immune response of mice to S III was studied. Pneumococcal polysaccharide is cleared from the circulation of mice in a markedly heterogeneous manner. Specifically immunized mice clear polysaccharide in an accelerated fashion. 1·25 μg of passively administered rabbit anti-S III antibody resulted in a distinct increase in clearance rate. The immune response of mice to S III is characterized by a rapid (peak titers at 4–7 days) and relatively weak response. Boosting with S III at 35 days after primary immunization did not result in a secondary response.