Problems in Immunology 147 



of glucose in the specific polysaccharide of Type II pneu- 

 mococcus was in the form of 1,4,6-branch points. This 

 not only accounted for the cross reactions of the poly- 

 glucoses in Type II antiserum, but also led to our dis- 

 covery of the serological activity of glycogen and amylopec- 

 tin, both of which contain 1,4,6-branch points of glucose. 

 But the cross reactivities of the polyglucoses in Types VII, 

 IX, XII, XX, and XXII antipneumococcal sera remain 

 unexplained, since we do not even know the component 

 sugars in the specific polysaccharides of these pneumococ- 

 cal types, let alone their linkages. Knowledge of the reac- 

 tion in Type XVIII antiserum is not quite so limited, for 

 Markowitz and I have shown that the specific polysac- 

 charide of this pneumococcal type consists mainly of glu- 

 cose, with smaller proportions of rhamnose and secondarily 

 bound phosphate. Most likely, 1,4,6 linkages are not pres- 

 ent on any glucose units of the Type XVIII polysaccharide, 

 since there is no cross reaction in either direction with 

 Type II, in spite of the occurrence of rhamnose in both 

 polysaccharides. It is therefore evident that the chemical 

 nature of the polyglucose specificities cannot be fully un- 

 derstood until the component sugars and fine structures of 

 the specific polysaccharides of more of the cross-reacting 

 pneumococcal types are elucidated — a formidable but by 

 no means insuperable task. 



Another far-flung immunological specificity which is 

 being unraveled is that of the polygalactoses, and among 

 these I include not only the galactans, but the already 

 mentioned plant gums, since most of these contain galactose 

 in their repeating units. Thus far, the specific polysac- 

 charide of only one pneumococcal type, XIV, has shown 

 this property. Goebel, Beeson, and Hoagland found it to 

 consist of three molecules of galactose to one of N-acetyl- 

 glucosamine, but did not establish any of the linkages. It 

 was therefore not too farfetched, when Wolfrom and his 

 collaborators isolated a galactan from the heparin mother 



