Antigenic Relationships of Pneumococci to Erythrocytes and Organs of Men and Animals

Summary The agglutination of human erythrocytes by antipneumococcal type XIV horse sera is only one very striking instance of antigenic relationships between pneumococcal antigens and substances present in organs of animals. The erythrocytes of rabbits and cats are also agglutinated by antipneumococcal type XIV horse sera, and in many instances also by the antibody against type VII. The antigenic relationship between rabbit blood cells and pneumococcus type XIV explains why antipneumococcal type XIV sera from rabbits do not contain the hemagglutinin for human blood cells. The type-specific (anti-carbohydrate) antibody is the bearer of the relationship between pneumococcus type XIV and human erythrocytes. Human organs absorb the hemagglutinating quality out of type XIV antipneumococcal horse sera, and saline extracts from human organs are flocculated by such sera. Erythrocytes of dog, pig, sheep and guinea pig are not agglutinated by antipneumococcal horse sera.