[The reaction of calves to parenteral administration of cyclopheosphamide]

One single injection of 50 mg/kg live weight cyclophosphamide or more to calves was followed by a latency of few days after which pneumonia or enteritis developed and caused death within one or two weeks. Cyclophosphamide application led to pronounced changes in the white blood count characterised, at the beginning, by rise of neutrophilic granulocytes and decline of lymphocates. Primary rise of granulocytes then was followed by almost complete disappearance of them. In those calves that survived the parameters of the white blood count were not restoredto normal until several weeks had elapsed. While an injection of 30 mg/kgcyclophosphamide usually was tolerated without any visible clinical reaction, it was also accompanied by the above pronounced changes in the white blood count. The activity of the reticulohistiocytary system, as recordable by means of ink and bacterial clearance, was not markedly affected by one single injection of 30mg/kg or 40 mg/kg cyclophosphamide. Calves with cyclophosphamide treatment exhibited unambigous humoral immune response, yet somewhat delayed or reduced in comparison to controls. While one single intravenous injectionof 30 mg/kg cyclophosphamide alone failed to trigger any clinical disease, it proved to be capable of rendering calves more susceptible to pneumonia pathogens. It, therefore, might be suitable for supporting experimental infection and thus facilitating the study of enzootic pneumonia of calf which usually is difficult to reproduce.