Response of Canine Fetuses and Neonates to Antigenic Stimulation

Canine fetuses of the same litter of beagles were injected with keyhole limpet hemocyanin (KLH), Mycoplasma gallisepticum, infectious bovine rhinotracheitis (IBR) virus or chicken erythrocytes. Three litters injected at gestation days 41, 47 or 51 produced no antibodies. Fetuses of a litter injected at gestation day 55 with 10 µg, 100 µg or 1000 µg of KLH and challenged with 1000 µg KLH 21 days after birth gave only a primary response. Fetuses of a litter infected with Brucella canis at gestation day 50 and killed 9 days later produced agglutinating antibodies. When 1-day-old pups were injected with KLH and challenged with the same antigen 40 days later, a secondary immune response was observed. When 1-day-old pups were injected with IBR virus, neutralizing antibodies were produced within 2 weeks. It was concluded that the canine fetus becomes competent for antibody production close to term.