No abstract

No abstract

No abstract

No abstract

There is no convincing evidence in the literature that streptococcal hemolysin is an antigen; and it appears to be a generally accepted view that the titre of antistreptolysin, in the sera of normal animals, cannot be increased by immunisation with streptolysin. Experiments described in this paper show that the lack of antigenic activity is caused by the serum used in the preparation of streptolysin. Hemolytic streptococcal filtrates, prepared without serum, behave like any ordinary antigen and they can be used to titrate the antistreptolysin in the sera of normal or immunised animals. MethodsIn the following experiments streptococcal hemolysin, free from bacteria, has been prepared by two different methods. The first method is founded on the experiments of MeLeod (1): Hemolytic streptococci are grown for 12 hours in broth containing 20 per cent of normal horse serum and the culture is then filtered through a Maasen candle. The second method was described by Neill and Mallory (2): Hemolytic streptococci are grown for 16 hours in broth which does not contain serum but which is enriched with yeast extract prepared as described by ThjStta and Avery (3). Air is excluded from the cultures during incubation by covering the medium with a heavy vaseline seal. Preliminary ExperimentsNeiU and Mallory (2) have shown that streptolysin, prepared by their method, is exceedingly sensitive to oxygen; they consider that their active hemolysin is oxidised to an inactive substance much more readily than methylene white is oxidised to methylene blue. They found that a shallow layer of active hemolysin was oxidised to an inactive substance in 6 hours at 38°C. when exposed to atmospheric oxygen and that the titre was only slightly reduced by the same period of incubation if air was excluded by a vaseline seal. They also found 267