Observations on the agglutination of polysaccharide-treated erythrocytes by tularemia antisera

Erythrocytes treated with polysaccharide from Past. tularensis are specifically agglutinated by the sera of persons recovered from tularemia or vaccinated against it, and by the sera of animals immunized with living cultures. The serum hemagglutination titer is correlated with the amount of antibody as measured by the quantitative precipitin method with polysaccharide, but not with the bacterial agglutination titer. The meaning of the results is discussed.