Preparative Changes Necessitated by a Quantitative Study of Precipitating Power of Pneumococcus Polysaccharides.

Abstract

In an extension of the quantitative study of the precipitin reaction between the specific polysaccharide of Pneumococcus III (S III) and homologous antibody it was found that several S III preparations which precipitated the same amount of antibody from horse serum threw down widely varying quantities of antibody from a rabbit serum. The present preliminary report deals with experiments on S II and S III undertaken to find the cause of variations in the precipitating power of these substances toward homologous rabbit antisera. 1. Specific Polysaccharide of Type III pneumococcus (S III). A Chamberland filtrate of 24-hour cultures in phosphate meat infusion glucose broth was concentrated about 12-fold in vacuo and precipitated several times with an equal volume of alcohol. The caseous S III was redissolved and separated from protein over the barium salt with barium chloride. Barium was removed by repeated reprecipitation of the S III with glacial acetic acid after addition of sodium acetate. The properties of several lots obtained in this way are given in the table. Preparations in which heat and strong acid were avoided showed far greater viscosity than did samples prepared by the original method. Comparison of viscosities was made in 0.9% salt solution. As will be seen from the table a new preparation precipitates approximately the same amount of antibody from serum as does the original culture filtrate. The new preparations precipitate more antibody from Type III antipneumococcus rabbit serum than those prepared by the original method, although all precipitate about the same amount of antibody from homologous horse antiserum. The sera used were first absorbed with “C”-polysaccharide and pneumococcus protein so that the remaining antibody would be mainly anti-S.