“…S. typhimurium antiserum provided no heterologous protection against E. coli endotoxin. The immunization schedule is simple, side effects are minimal, and "O" antibody response compares favorably with that achieved after two injections of typhoid vaccine a month apart (11,12). Immunoglobulin fractionation studies were not performed because it has been shown that both 7S and 19S fractions contain protective "O" antibody (6 In contrast to the excellent protection against homologous endotoxins, these human antisera against smooth organisms were of no value in preventing the Shwartzman reaction or death from heterologous endotoxins.…”