STUDIES ON BACILLUS TYPHOSUS TOXIC SUBSTANCES : III. THE EFFECT OF SERA UPON THE INJURY PRODUCING FACTORS OF THE PHENOMENON OF LOCAL SKIN REACTIVITY.

It has been demonstrated that many multiples of minimal doses of Bacillus typhosus reacting factors can be neutralized by specific immune sera. The potency of a given serum can be conveniently titrated against increasing amounts of reacting factors. If the immune serum is diluted or if the amount of the reacting factors is too large for a given amount of serum, there is obtained neutralization but only irregularly. Normal and heterologous sera (therapeutic meningococcus and erysipelas horse sera) free of normal agglutinins or possessing normal agglutinins of a low titer (1:16) for Bacillus typhosus are not able to neutralize the reacting factors. There is obtained questionable neutralization with a serum possessing normal Bacillus typhosus agglutinins in dilution 1:64. The titer of the neutralizing antibodies increases in the course of immunization. Immune sera exercise a definite protection against the mortality induced by intravenous injection of Bacillus typhosus culture filtrates.