title: Is Infant Immunity Actively Suppressed or Immature?
abstract: 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, CD8posT cells and NK cells have defective cytolysis and cytokine production, and CD4posT cell responses tend to bias towards a Th2 phenotype and promotion of regulatory T cells (Tregs). The basis for these differences is not well understood and may be in part explained by epigenetic differences, as well as immaturity of the infant's immune system. Here we present a third possibility, which involves active suppression by immune regulatory cells and place in context the immune suppressive pathways of mesenchymal stromal cells (MSC), myeloid-derived suppressor cells (MDSC), CD5posB cells, and Tregs. The immune pathways that these immune regulatory cells inhibit are similar to those that are defective in the infant. Therefore, the immune deficiencies seen in infants could be explained, in part, by active suppressive cells, indicating potential new avenues for intervention.
authors.affiliation: Seattle Biomedical Research Institute and the University of Washington Departments of, Seattle WA.
authors.forename: Ana L
authors.initials: AL
authors.lastname: Gervassi
authors.affiliation: Seattle Biomedical Research Institute and the University of Washington Departments of, Seattle WA ; Medicine, Seattle WA ; Global Health, Seattle WA.
authors.forename: Helen
authors.initials: H
authors.lastname: Horton
keywords: immune suppression; infant immunity; infant vaccines