ABSTRACT
In this chapter we discuss immune system ontogeny and cover various aspects of neonatal immunology. We briefly describe embryological development of the immune system prior to birth and explain how this develops further during the early life of animals. Neonatal protection against infection is discussed, in terms of the beneficial effects of maternally derived antibodies present in colostrum and milk. The mechanism of absorption of IgG into the blood following ingestion of colostrum is described. The benefits of passive transfer of maternally derived antibody is balanced against their interference with vaccination of young animals. We provide examples of failure of passive transfer of immunity. The pathogenesis of neonatal isoerythrolysis is illustrated and the clinical consequences discussed.
