Comparison of the Potency of Polyvalent Antimeningococcus Serum Produced with Four and Six Representative Strains and That Produced with Sixty Strains, as Determined by the Agglutination Titer

The potency of a polyvalent antimeningococcus serum, as tested by its agglutination titer, was sacrificed by immunization with a large number of strains of the meningococcus. By immunization with a limited number of representative strains, four or six, carefully selected on account of their antigenic and agglutination properties, the potency was increased three- to tenfold without sacrificing the polyvalency; that is, as tested with at least 70 heterologous strains of the meningococcus. The agglutination titer, unfortunately, is not an entirely satisfactory criterion of therapeutic potency, but it is the only practical method available that determines also the polyvalent action of antimeningococcus serum.