ERYTHROCYTE AFFINITY AND BIOLOGICAL ACTIVITY OF TYPHOID ENDOTOXIC EXTRACT

A solution of a dehydrated extract derived from Salmonella typhi (TO-901) produced effects characteristic of endotoxins, reacted specifically with homologous antibodies, and was capable of modifying erythrocytes for hemagglutination. The affinity for erythrocytes was enhanced by heating or NaOH treatment of the antigen. Ultracentrifugation of the NaOH-treated material revealed a single, rather narrow peak, migrating with a sedimentation rate of 7 to 8. These were the smallest elements with antigenic determinant groups and comprised both erythrocyte-attachable and non-attachable particles. Attempts to release the antigen from modified erythrocytes failed. Removal of particles with red cell affinity from the endotoxic solution did not measurably reduce its antibody-neutralizing capacity, nor its toxicity to rabbits challenged with epinephrine. Rabbits injected with autologous erythrocytes modified with large (500 μg/ml) amounts of antigen and subsequently washed 6 times showed a moderate response, both with...