The results of six different methods of assaying types I and II antipneumococcic horse serums by single titrations have been described, and the correlation of each method with mouse protection values calculated. The method chosen as a substitute for the animal test is a precipitin test with closely spaced serum dilutions and with soluble specific substance as the antigen. Compared with mouse protection values, correlation coefficients of 0.930 ±0.012, and 0.817 ±0.031 were obtained for types I and II antibodies respectively. Equations were derived which permit satisfactory prediction of mouse protection values from those of the precipitin test.


This is one of a series of studies on pneumonia being conducted under a grant from the Commonwealth Fund of New York.

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