The immune response of foetal calves

The immunological response of foetal calves to tetanus toxoid was investigated. Emphasis was placed on foetal immunocompetence and how this related to responses seen in adult cattle. The establishment of indwelling cannulas in the efferent prescapular lymphatic ducts and superficial veins of foetal calves allowed continual monitoring of cellular and humoral changes in efferent lymph and peripheral blood. Foetal calves from 195 to 253 days gestational age had the capacity to mount cell-mediated and humoral immune responses of similar character and magnitude as adult cattle to tetanus toxoid. Intravenous and subcutaneous routes of challenge with tetanus toxoid resulted in specific antibody production which peaked 26 to 31 days after vaccination. Significant tetanus toxoid-stimulated lymphocyte proliferation was present 4 to 6 weeks after vaccination with tetanus toxoid in both a foetus and an adult. After antigenic challenge lymphocytes remained the predominant cell type in efferent prescapular lymph of foetuses and cows while at the same time a marked shift to the left, characterised by band neutrophils and neutrophilic metamyelocytes occurred in peripheral blood. Lymph flow rate increased and cell concentration decreased after antigenic challenge.