Production of IFN-γ by PBMCs stimulated with IL-12 and IL-18. PBMCs (50 000 cells per well) obtained from 5 patients with lymphoma after autologous stem cell transplantation (▨) or from 5 healthy control subjects (▪) were incubated in vitro in medium alone or medium containing IL-12 10 U/mL, IL-18 10 ng/mL, or both cytokines as indicated. IFN-γ levels in supernatants were measured by ELISA. Values are means; error bars indicate SE. Absence of visible error bars indicates SE ≤ 1 pg/mL. The P values for comparison of patient versus control subject results are as follows: ≤ .05 (*), ≤ .025 (**).