T-cell proliferation and cytotoxicity are impaired following stimulation with HCMV-infected DCs.

(A) Influenza virus–specific T-cell proliferation is shown following stimulation of T cells with HCMV-infected DCs. 10⁵ T cells per well were stimulated at different T cell–DC ratios either with HCMV-infected or mock-infected DCs which were also infected with influenza as described in “Patients, materials, and methods.” T-cell proliferation was measured by adding ³H-thymidine to the cells in the last 16 hours of a 5-day in vitro culture. Means of³H-thymidine uptake (cpm) are shown from triplicate wells. (B) Influenza virus–specific T-cell cytotoxicity is shown using HCMV-infected or mock-infected DCs as stimulators. Immature DCs (day 7) from an HCMV-seronegative HLA-A2⁺ donor were either infected with HCMV_TB40/E (MOI = 10) (▴) or were mock infected (●) for 48 hours and then both groups of DCs were incubated with influenza virus for 6 hours prior to adding them to autologous T cells (T cell–DC ratio = 10:1) in bulk cultures, as described in “Patients, materials, and methods.” Mock-infected DCs (■) to which influenza virus was not added served as controls to detect nonspecific T-cell stimulation. CTL assay was carried out 7 days later against influenza M1 peptide-pulsed autologous BLCL target cells or unpulsed target cells. Lysis of unpulsed targets was significantly lower by each group of T cells than that of peptide-pulsed targets, and is not shown. Means and standard deviations of percentage specific lysis from triplicate wells are shown.