Kinetics of detection of blastogenic responses of neonatal calves inoculated in utero with tetanus toxoid, killed Mycobacterium bovis, and killed Brucella abortus.

Nine pregnant cows were laparotomized and their fetuses were immunized with tetanus toxoid, killed Brucella abortus, and killed Mycobacterium bovis. Blastogenesis assays and total leukocyte and differential counts were done when the calves were 1, 2, 3, 7, 14, 21, 28, and 60 days of age. Initial blastogenesis responses to antigens, phytohemagglutinin, and concanavalin A were not positive as frequently as were the responses obtained when the calves were 2 to 3 weeks of age. The probability of obtaining a positive response to an antigen was positively correlated with the magnitude of the response, as determined by delayed-type hypersensitivity skin reactions. Leukocyte and differential WBC counts in immunized calves were similar to those of unimmunized calves. The mean leukocyte count for the immunized calves remained near 16,000 cells/mm3; blood obtained in the first few days after birth contained a greater number of neutrophils than lymphocytes, whereas lymphocyte-to-neutrophil ratio gradually approached those of adult cattle, in which lymphocytes predominate.