Post-HSCT monocyte suppressor activity affects post-HSCT T cells. (A) Total PBMCs obtained from a control (□) or an HSCT recipient (▪) were stimulated by highly enriched allogeneic control monocytes and proliferative responses were determined by [³H]thymidine incorporation after 5 days of culture. (B) Highly enriched T cells (Tc) or T cells cocultured with their autologous monocytes (Tc/m) of controls (□) or of HSCT recipients (▪) were stimulated by allogeneic cells and their proliferative response determined as in Figure 5A. (C) In a crossover experiment, control monocytes were stimulators of allogeneic post-HSCT T cells (□) and, vice versa, post-HSCT monocytes were stimulators of allogeneic control T cells (▪), and the respective proliferative responses were determined as in Figure 5A. Error bars indicate SEM.