Prenatal immunization of the lamb to brucella; secondary antibody response in utero and at birth.

Pre-natal immunization has been investigated as a means of overcoming the non-reactivity of newborns to bacterial somatic antigens. Normal newborn lambs evidenced little or no antibody response to killed whereas the same dose of antigen elicited relatively high levels of antibody in foetuses late in the gestation period. When foetal lambs were immunized at midgestation they responded slowly and with low levels of antibody. The response was adequate, however, to prime for a secondary one and at birth. The secondary response occurred at the same time and with antibody levels as high as those attained in adult sheep on secondary stimulation. When secondarily stimulated at birth, a significant percentage of the neonates responded rapidly with high levels of antibody. As customarily found in older animals, IgG immunoglobulin appeared later and regressed more slowly than IgM.