146 Perspecfives in Microbiology 



polysaccharide of the same cellobiuronic acid. There was, 

 however, no "antigen in common," as the microbiologist 

 is wont to say in reference to cross reactions — only a chem- 

 ical grouping in common, for the Type VIII specific sub- 

 stance contains glucose in addition. The quantitative as- 

 pects of this reaction were carefully studied in our labora- 

 tory, and as a result, when cotton was oxidized to a poly- 

 cellobiuronic acid, it could be predicted that this new sub- 

 stance, soluble cotton, would turn out to be an immuno- 

 logically specific polysaccharide reactive with Type III and 

 Type VIII antipneumococcus sera. When Stacey isolated 

 a polysaccharide containing multiple cellobiuronic acid 

 groupings from Rhizobium radicicolum, this substance was 

 also found to react with Type III antiserum. The relation 

 between chemical constitution and the immunological re- 

 activity of the Type Ill-Type VIII pneumococcus group has 

 therefore been fairly well cleared up as far as the common 

 component, cellobiuronic acid, is concerned. The precise 

 function and points of attachment of the additional glucose 

 radicals in the Type VIII substance remain unresolved. 



Another immunologically cross reactive group of wide 

 occurrence might be termed the polyglucose group. Not 

 only do the dextrans formed by various Leuconostoc species 

 give cross reactions in a number of antipneumococcus and 

 antityphoid antisera, as shown many years ago by Zozaya 

 and Neill and Hehre, but these substances have been 

 found by Kabat to be antigenic in man. Depending upon 

 the synthesizing strain, dextrans contain glucose in a-1,6 

 linkage, with varying proportions of 1,4 linkages and, to 

 a smaller extent, 1,3 links. Some of the synthetic polyglu- 

 coses show a serological reactivity in antipneumococcal 

 sera much like that of the dextrans, which is not surpris- 

 ing since Pacsu has found that the synthetic products also 

 contain 1,6 and 1,4 linkages. 



A chemical clue to the nature of polyglucose specificities 

 was supplied by Stacey's report that all of the 30 per cent 



