Is Infant Immunity Actively Suppressed or Immature?

Almost 7 million children under the age 5 die each year, and most of these deaths are attributable to vaccine-preventable infections. Young infants respond poorly to infections and vaccines. In particular, dendritic cells secrete less IL-12 and IL-18, CD8 T cells and NK cells have defective cytolysis and cytokine production, and CD4 T cell responses tend to bias towards a Th2 phenotype and promotion of regulatory T cells (T).