Impaired fetal thymocyte development after efficient adenovirus-mediated inhibition of NF-kappa B activation

We introduce a new experimental system combining adenovirus-mediated gene t ransfer and fetal thymic organ culture (FTOC), This system allowed us to ef ficiently express in developing thymocytes a mutant form of the NF-kappa B inhibitor I kappa B alpha (mut-I kappa B) and to study the maturation defec ts occurring when NF-kappa B activation is inhibited during fetal developme nt. Fetal thymocytes infected with adenovirus containing mut-I kappa B were found to develop normally until the CD44(-)CD25(+), CD4(-)CD8(-) double;ne gative stage, while production of more mature double-positive and single-po sitive populations was strongly decreased. Proliferation, as measured by th e percentage of cells in cycle appeared normal, as did rearrangement and ex pression of the TCR beta-chain, However, apoptosis was much higher in FTOC infected with adenovirus containing mut-I kappa B than in FTOC infected wit h a control virus, Taken together, these results suggest that NF-kappa B pl ays a crucial role in ensuring the differentiation and survival of thymocyt es in the early stages of their development.