Reduced surface expression of transforming growth factor β receptor type II in mitogen-activated T cells from Sézary patients

Sézary syndrome (SzS), the leukemic form of cutaneous T-cell lymphoma, is characterized by clonal proliferation of CD4⁺ T cells and immune dysfunctions, raising the possibility of cytokine-related abnormalities. We previously described a decreased response to the growth-inhibitory effects of transforming growth factor type β (TGF-β) in SzS T cells accompanied by apparent loss of surface type IITGF-β receptor (TGFβRII). To specifically determine if defects exist in TGFβRII protein expression and/or transport in SzS patients, we developed a sensitive flow cytometric method to detect TGFβRII on the surface and intracellularly in the CD4⁺ T cells. Our results indicate that unlike normal CD4⁺ T cells, CD4⁺ T cells from 9 of 12 SzS patients expressed little, if any, surface TGFβRII in response to mitogen stimulation. At the intracellular level, however, pools of TGFβRII were comparable to those in normal CD4⁺ T cells. This indicates that defective trafficking of this inhibitory cytokine receptor may contribute significantly to the development of this disease.