Three strains of R. tsutsugamushi, Karp, Mitani and Tanizawa strains, were inoculated into the peritoneal cavity of guinea-pigs previously injected with chlorpromazine. The peritoneal exudates of thus treated guinea-pigs were diluted with physiological salt solution and were used as the compliment-fixing antigens. The sera of rabbits immunized with living rickettsiae were used as the antisera. The compliment fixation test was carried out in the conventional way. The results are summarized as follows: 1) The peritoneal exudates showed a high compliment-fixing antigenicity, but did not show any anti-compliment-fixing antigenicity. 2) In the presence of homologous and heterologous antisera, the antigen of Karp strain did not show any significant difference in the suppression titer of hemolysis. 3) In both of homologous and heterologous antisera, the antigen of Mitani strain showed strong compliment-fixing action. 4) The antigen of Mitani strain had a compliment-fixing antigenicity, showing no noticeable difference in the suppression titer of hemolysis in both of homologous and heterologous antisera.
Consequently, the peritoneal exudates of guinea-pigs treated as mentioned above, in regard to compliment-fixing antigenicity, have the same rickettsial specificity, but no noticeable strain specificity.