Specific Proteins of Antipneumococcus Sera Ii. Immunological Fractionation 01~ Type I Antipneumococcus Horse and Rabbit Sera

In the preceding paper of this series (1) it was reported that the amount of specific antibody precipitable by the capsular polysaccharide is related to the mouse protective value of Type I antipneumococcus serum only under certain well defined conditions. Thus with Type I antipneumococcus rabbit serum there was a direct proportionality between the two determined values. The protective ratio for immune rabbit serum, that is, the number of protective units per rag. of specifically precipitable nitrogen, was, however, higher than that for Type I antipneumococcus horse serum. Moreover, it was found that with the latter there existed at least two different protective ratios. Thus antipneumococcus rabbit sera average 1170 mouse protective units per rag. of specifically precipitable nitrogen, whereas horse sera fall into two groups having average values of 540 and 800 units per rag., respectively.