In vitro activation of healthy T cells and adoptive transfer. (A) CD4⁺ and (B) CD8⁺ T cells derived from healthy C57/BL6 IRF4^+/+ mice were activated with CD3/CD28 beads and coincubated with CLL tumor cells derived from the spleen of either Tcl-1 tg IRF4^+/+ or Tcl-1 tg ΔB/ΔB leukemic mice for 24 hours. The activation status of T cells was measured using CD25 and CD69 antibodies by flow cytometry. (C) IFN-γ secretion was measured 72 hours after CD3/CD28 bead activation in cell culture supernatants using enzyme-linked immunosorbent assay and (D) intracellular flow cytometry. (E) CLL tumor cells derived from the spleen of either Tcl-1 tg IRF4^+/+ (red) or Tcl-1 tg ΔB/ΔB (blue) leukemic mice were transplanted into C57/BL6 WT (solid lines) or NOD-SCID recipients (dashed lines) using intraperitoneal injection. Overall survival of recipient mice is shown as Kaplan-Maier analysis. (F) Naïve and (G) antigen-experienced CD4⁺ and CD8⁺ T cells derived from the spleen of Tcl-1 tg IRF4^+/+ or Tcl-1 tg ΔB/ΔB tumors transplanted in C57/BL6 recipients.