Monocyte rescue of human T cells from apoptosis is CD40/CD154 dependent

The induction of T-cell apoptosis is regulated in part by monocytes (CD14() cells). Human peripheral blood monocytes inhibited the spontaneous cell d eath of activated T cells in vitro. The inhibition of T-cell apoptosis did not require autologous monocytes. Inhibition required direct contact with m onocytes and was not due to a soluble factor. Furthermore, treatment of mon ocytes with actinomycin D, cycloheximide and paraformaldehyde abrogated the anti-apoptotic activity of these cells. Blocking antibody to CD40 and CD15 4 (CD40 ligand) decreased the ability of monocytes to aid in T-cell surviva l, whereas, blocking LFA-1/I-CAM-1, Fas ligand and the CD4/major histocompa tibility complex class II interaction did not affect the influence of monoc ytes on T-cell survival. This shows that monocytes rescue of activated T ce lls from apoptosis is dependent upon CD40/CD154 interaction.