CD4(-CELLS KILL CD8(+) T-CELLS VIA FAS() T)FAS LIGAND-MEDIATED APOPTOSIS/

To explore the possibility that CD4(+) T cells, described to mediate t he elimination of themselves or B lymphocytes, could also mediate the elimination of CD8(+) T cells, we analyzed apoptotic phenomena in cocu ltures of CD4(+) and CD8(+) autologous T cell lines. The data show tha t CD8(+) T cells were lysed by activated CD4(+) helper T cells by a Fa s/FasL-mediated mechanism. CD4(+) T cells were not lysed by activated CD8(+) T cells, although Fas and Fast were equally expressed and anti- fas Abs induced apoptosis in both CD4(+) and CD8(+) T cell populations , The results allowed us to speculate that CD4(+) T cells not only hel p CD8(+) T lymphocytes to mature into effector killer cells and to sus tain this function but can also limit their growth.