WT1-CTL are detected in MM patients pretransplantation and are negatively associated with disease severity. Pretransplantation frequencies of WT1-CTL in the PB of MM patients were quantified by intracellular IFN-γ assay or MHC-tetramer analyses. (A) Percentage of CD3⁺ cells in healthy donors and MM patients producing IFN-γ in response to nonpulsed autologous PBMC, or PBMC pulsed with WT1 peptide pools. (B) Absolute numbers of CD3⁺ cells producing IFN-γ in response to nonpulsed or WT1 peptide pool–pulsed PBMC were quantified by multiplying the percentage of cells producing IFN-γ by the patient's absolute lymphocyte count. (C) Comparing disease severity in patients with greater or less than 10 WT1-CTL/μL of PB. Absolute numbers of WT1-CTL were determined by IFN-γ or MHC-tetramer analyses and compared with pretransplantation M-Spike gamma levels. *P ≤ .0003, 2-tailed Wilcoxon matched pairs signed rank test; Δ, P ≤ .0303, 2-tailed Mann-Whitney test.