title: Neonatal CD8+ T-cell differentiation is dependent on interleukin-12.
abstract: Neonatal CD8(+) T-cell activation is significantly impaired compared with that in adults. Recent studies have demonstrated that interleukin (IL)-12 is necessary as a third signal, in addition to antigen and co-stimulation, to authorize the differentiation of naive CD8(+) T cells. We examined whether human neonatal CD8(+) T cells, which possess an exclusively naive T-cell phenotype, required a third signal to authorize a productive T-cell response. IL-12 enhanced activated naive CD8(+) T-cell survival, expansion, CD25 expression, and IL-2 production. Activated CD8(+) T cells produced interferon-γ and intracellular granzyme B and were cytotoxic only in the presence of IL-12. Sustained IL-12 signaling for 72 hours was required for optimal interferon-γ production. IL-12, in concert with T cell receptor (TCR) stimulation, sustained late-stage (48-72 hours) intracellular phosphorylation and particularly total protein levels of the proximal TCR components, Lck, and CD3ξ. The requirement for a third signal for productive human neonatal CD8(+) T-cell differentiation may have implications for neonatal vaccination strategies.
authors.affiliation: National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin, Ireland. mark.mccarron@ucd.ie
authors.forename: Mark J
authors.initials: MJ
authors.lastname: McCarron
authors.forename: Denis J
authors.initials: DJ
authors.lastname: Reen
mesh_terms: D018414:CD8-Positive T-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation; D005312:Fetal Blood / Q000166:cytology; D006801:Humans; D007231:Infant, Newborn; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000276:immunology / Q000378:metabolism*; D008213:Lymphocyte Activation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D011948:Receptors, Antigen, T-Cell; D018664:Interleukin-12; D007371:Interferon-gamma