Functional characterization of an IL-7-dependent CD4+CD8αα+ Th3-type malignant cell line derived from a patient with a cutaneous T-cell lymphoma

CDR3 of the functional rearranged T-cell receptor variable beta region (TCR-V beta) transcript was sequenced in order to demonstrate for the first time the identity between a long-term cultured T-cell line derived from a cutaneous T-cell lymphoma (CTCL) patient and the malignant T-cell clone present in the blood. The patient's peripheral blood lymphocyte-derived cultured T-cell line had a CD3(+)V beta 22(+)CD4(+)CD8 alpha alpha(+)CD25(-) phenotype. It was named Pno and had been cultured for more than 1 year. Both fresh and long term-cultured tumor cells proliferated highly in response to interleukin-7 (IL-7), and exogeneous IL-7 prevented Pno lymphocytes from apoptosis and maintained high levels of Bcl-2 expression, This unique malignant cloned lymphocyte line was further used to carry out functional studies. The results indicated that the CD3/TCR structures expressed by the Pno lymphocytes were functional because an immobilized anti-CD3 monoclonal antibody (mAb) or the combination of a soluble anti-CD3 mAb with submitogenic doses of phorbol 12 beta-myristate 13 alpha-acetate induced a proliferative response, Further, the CD2 and CD28 coreceptors were functional because they were able to induce a strong proliferative response upon their specific stimulation. Finally, the Pno T cell line had a Th3-type cytokine profile because it produced high amounts of the immunosuppressor cytokine tumor growth factor-beta 1 (TGF-beta 1), This high production of TGF-beta 1 may inhibit antitumor specific responses in CTCL. (C) 2000 by The American Society of Hematology.