Abstract
In previous reports 1 from this laboratory, it has been shown that free antibody can be recovered from the immune precipitate or agglutinate of Type I pneumococcus by treating with dilute acid which causes a shift of the antigen-antibody equilibrium. The present communication extends our observation to the immune precipitate of another organism, Type B Friedländer bacillus.
Antisera of horse and rabbit origin were prepared by immunizing animals with heat-killed Type B Friedländer bacilli. The specific polysaccharide of this organism was prepared according to the method of Heidelberger, Goebel, and Avery. 2 Polysaccharide was added to the antisera to form the specific precipitate. The precipitate was washed and suspended in 2% or 3% NaCl solution. The use of NaCl increases the percentage of recovery by decreasing the solubility of the precipitate. 3 Four cc portions of the suspension, containing about 5 mg N, were treated with equal volumes of dilute HCl of different concentrations according to the procedure previously described. 3 The percentage of recovery and the solubility of “acid-precipitates” (that is, the precipitate from which a part of the antibody has been set free by acid) at different pH's were calculated. Results are shown in Fig. 1. For the sake of comparison the curves for Type I pneumococcus previously reported 3 are also shown in the figure.
For the precipitate obtained with horse serum in 1% NaCl, the optimal pH for recovery was 3.25, while for that with rabbit serum in 1.5% NaCl, the optimal pH was 3.50. These pH values are distinctly different from those (2.75 and 2.70) found for Type I pneumococcus under similar conditions.
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