Recently, considerable interest has developed in passive immunization against pertussis. In this respect, adult immune serum, convalescent serum and hyperimmune human serum have received particular attention. The last type of serum is protective against the experimental murine disease.1 When injected in doses varying from 10 to 40 cc. it also increases the opsonocytophagic reaction and the agglutinating titer of the blood of infants.2 Moreover, recent preliminary reports3 have indicated that the administration of hyperimmune human serum is effective in preventing or modifying the disease in infants exposed to pertussis.
Because of the apparent limitations that may exist in large scale production of hyperimmune serum, effective as it may be, our attention has been directed to the investigation of the value of immune rabbit serum. An immune serum prepared by injecting suspensions of living organisms into rabbits was found to protect mice against the experimental disease.4 The