Abstract
The presence of phosphorylcholine in pneumococcal capsular polysaccharides was examined by using monoclonal antiphosphorylcholine antibody. Of the 83 known capsular types of Streptococcus pneumoniae, 6 types, viz., 24A, 27, 28F, 28A, 32F, and 32A, gave a positive capsular reaction (quellung) which could be inhibited by phosphorylcholine. The capsular polysaccharides of these six types, therefore, contain phosphorylcholine.