SEs induce STAT3 phosphorylation in primary malignant T cells cultured with nonmalignant T cells. (A) Representative flow cytometric analysis of freshly purified PBMCs from a CTCL patient stained with CD3, CD4, CD26, and a TCR-Vb panel. Bar plots demonstrate TCR-Vb repertoire of the malignant (CD3⁺, CD4⁺, CD26⁻) T-cell compartment and the nonmalignant (CD3⁺, CD4⁺, CD26⁺) compartment. (B) CD4⁺/CD26⁻ (malignant T cells) and CD4⁺/CD26⁺ (normal T cells) were separated by FACS from freshly purified PBMCs from a CTCL patient. CD4⁺/CD26⁻ and CD4⁺/CD26⁺ T cells were mono- and cocultured with either vehicle (PBS) or SEA (200 ng/mL) for 24 hours. After incubation, cells were stained for pY-STAT3. Intensity of pY-STAT3 staining is shown in the contour plot. “PBS + Non-malignant” signifies gated malignant T cells cocultured with nonmalignant T cells and stimulated with vehicle, and vice versa for “SEA + Malignant.”