The reduced incidence of graft versus @entity2132 following the use of @entity1 cord blood as a source of stem cells for bone marrow reconstitution challenges our understanding of the immunocompetence of newborn T cells. Newborn @entity404 + T cells express mainly the CD45RA phenotype and have been considered to respond comparably to adult @entity404 + T cells exhibiting the CD45RA phenotype. We compared the in vitro kinetics of phenotypic conversion of newborn and adult @entity404 +CD45RA+ T cells to @entity404 +CD45RO+ T cells. The cytokine profile and B cell helper activity of the converted @entity404 +CD45RO+ T cell population were also determined. Newborn @entity404 +CD45RA+ T cells were converted to @entity404 +CD45RO+ with significantly faster time kinetics than adult @entity404 +CD45RA+ T cells, following either phytohaemagglutinin (PHA) or anti- @entity3138 activation. Freshly purified newborn naive T cells did not produce @entity1199 , @entity3646 or @entity379 ( @entity379 ) following stimulation, whereas adult naive T cells secreted @entity1199 and adult-derived @entity404 +CD45RO+ T cells secreted all three cytokines under the same stimulatory conditions. However, newborn and adult @entity404 +CD45RA+ T cells, following primary stimulation and maturation in vitro, acquired the ability to secrete a Th1-type cytokine profile of @entity1199 and @entity379 after secondary stimulation. Newborn @entity404 + naive T cells that acquired the CD45RO phenotype in vitro also gained B cell helper activity equivalent to that of adult in vitro matured @entity404 + naive T cells. These findings suggest that newborn and adult @entity404 +CD45RA+ T cell subsets are differentially responsive to various stimuli. They show that newborn @entity404 +CD45RA+ naive T cells can transform more quickly than their adult counterparts into functionally equivalent @entity404 +CD45RO+ T cells, a process that may be important to counteract the immature immune environment which exists in the newborn.

Rapid conversion of naive to effector T cell function counteracts diminished primary XXXX newborn T cell responses.

@entity1 :: ('9606', 'Species') :: ['human'] @entity404 :: ('920', 'Gene') :: ['CD4'] @entity3138 :: ('914', 'Gene') :: ['CD2'] @entity2132 :: ('MESH:D006086', 'Disease') :: ['host disease'] @entity379 :: ('3458', 'Gene') :: ['IFN-gamma', 'interferon-gamma'] @entity1199 :: ('3558', 'Gene') :: ['IL-2'] @entity3646 :: ('3565', 'Gene') :: ['IL-4']
@entity1 :: (9606,Species) :: ['human']
