Neonatal immunity: how well has it grown up?

Several factors are conspiring to focus attention on neonatal immunology. First, the dogma that neonatal exposure to antigen results in tolerance rather than immunity has been challenged. Second, there is a clinical imperative; the development of effective neonatal vaccines is likely to be extremely important in reducing infant morbidity and mortality, and the successful use of cord blood stem cells for bone marrow reconstitution calls for a better understanding of the regulation of responsiveness in neonatal lymphocytes. Third, recent evidence suggests that exposure to high levels of antigen during early life might contribute to the increasing prevalence of allergic diseases.