Blood samples are collected and analyzed by quantitative CMV PCR, chromium release assays for CMV pp65-specific cytotoxicity, and immunophenotype for CD3, CD4, CD8, CD56, CD19, and CD45 RA/RD. Intracellular cytofluorometry is used to assess IL-2, IL-4, IL-10, and IFN-γ production by CD4 and CD8 CMV-specific effector cells.