title: Overexpressed Bcl-x(L) prevents bacterial superantigen-induced apoptosis of thymocytes in vitro.
abstract: bcl-x, a homologous gene of bcl-2, has an anti-apoptotic function and appears to play a critical role in the development of lymphoid systems. To investigate the effect of overexpressed Bcl-x(L) on the development of T lymphocytes, we established two lines of transgenic mice by using Emu-chicken bcl-x(L) (cbcl-x(L)) transgene, where the cBcl-x(L) protein was expressed mainly in lymphoid cells. Although thymocytes and splenocytes from cbcl-x(L) transgenic mice are resistant to apoptosis in vitro, clonal deletion of thymocytes, recognizing endogenous self-superantigens in the thymus, still normally proceeded and no self-reactive T cells were found in the spleen of the transgenic mice. To dissect clonal deletion, we utilized two in vitro models, thymocytes/antigen presenting cells co-culture system and fetal thymus organ culture system. In both, bacterial superantigen staphylococcus aureus enterotoxin B (SEB) induces apoptosis of T cells with Vbeta8+ T cell receptor (TCR) reacting to SEB, which mimics clonal deletion of self-reactive thymocytes in vivo. SEB-induced depletion of Vbeta8+ T cells from thymocytes when taken from the transgenic mice was effectively inhibited. The data might raise the possibility that cell death process involved in clonal deletion in the thymus is a form of apoptosis inhibited by Bcl-x(L).
authors.affiliation: Department of Medical Genetics, Biomedical Research Center, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.forename: H
authors.initials: H
authors.lastname: Honda
authors.forename: H
authors.initials: H
authors.lastname: Hirai
authors.forename: Y
authors.initials: Y
authors.lastname: Tsujimoto