Measurement of antibody-reactive toxin antigen during experimental staphylococcal B enterotoxemia

Staphylococcal enterotoxin B (SEB) injected intravenously is rapidly cleared from the circulation and deposited in tissues. Type-specific antiserum administered after toxin has left the circulation can influence the course of enterotoxemia, and this observation suggests that toxin antigens may either be returned to the circulation or reside on cell surfaces readily available to antibody. If SEB toxin or its fragments regain access to the extracellular space, they might react with circulating antibody and be detected and quantitated by the reduction in antibody titer. Accordingly, 1 h after toxin or saline injection, animals were given type-specific enterotoxin B antiserum, and the difference in titers between the animals was used to compute the amount of enterotoxin immediately available to antibody. Further, by measuring differences in titers over a 48-h period, an estimate was made of the amount of SEB antigen that gained access to antibody. The data indicate that rats, which are relatively resistant to the lethal effects of enterotoxin, clear toxin from the circulation promptly and that very little toxin reenters the circulation. Monkeys, who are highly susceptible to SEB, also clear toxin promptly. However, in contrasts to rats, monkeys have greater quantities of SEB immediately available to antibody and in addition return significant quantities of toxin antigens to the extracellular space.