The source of apoptotic material that drives the induction of a Treg phenotype in CTCL cells is common to CTCL and normal CD4 T cells. Coexpression of membrane CD3 or CD4 and cytoplasmic CTLA-4 was measured in responding CTCL cells by flow cytometry. (A) CTCL cells cultivated with nonloaded autologous DCs. (B) CTCL cells cultured with autologous CD3-treated apoptotic tumor-loaded DCs. (C) CTCL cells cultured with autologous apoptotic tumor-loaded DCs. (D) CTCL cells cultured with DCs pulsed with viable CD4-treated autologous CTCL cells. (E) CTCL cells cultured with nonloaded allogeneic DCs. (F) CTCL cells stimulated by autologous DCs loaded with allogeneic apoptotic CTCL cells. (G) CTCL cells cultured with autologous DCs pulsed with viable allogeneic CTCL cells. (H) CTCL cells stimulated by autologous DCs pulsed with allogeneic apoptotic CTCL cells. (I) CTCL cells cocultivated with nonloaded DCs. (J) CTCL cells responding to DCs fed autologous apoptotic CTCL cells. (K) DCs fed normal control CD4 T cells, treated with CD3, and γ-irradiated.