Neonatal bacillus Callmette-Guerin vaccination induces adult-like IFN-gamma production by CD4(+) T lymphocytes

The immaturity of the neonatal immune system in mice is associated with def ective IFN-gamma production and The-biased immune responses. In this study, infants vaccinated at birth with BCG produced similar concentrations of IF N-gamma in response to PPD and showed similar frequencies of IFN-gamma -pro ducing lymphocytes as compared to immune adults. Infants and adults produce d only low concentrations of IL-4 and IL-5. CD4(+) T lymphocytes were the m ain source of IFN-gamma. Similar proportions of Th1 and Th0 PPD-specific T cell clones were observed in infants and adults. This study demonstrates th at the human neonatal immune response to BCG is not biased towards Th2 and is characterized by the predominant production of lFN-gamma by CD4(+) T lym phocytes.