Functional properties in Sézary cells with an unusual phenotype

The immunological and functional characteristics of Sézary cells with an unusual phenotype are reported. The clinical, histologic, and hematologic picture was typical for Sézary syndrome. Studies with monoclonal antibodies showed that 80% Sézary cells had an CD3+, CD4+, CD5+, CD7-, CD8-, Leu-7+, Leu-8-, Leu-11-, OKM1- phenotype. By two-color immunofluorescence assay 80% FACS-sorted Leu-7+ cells coexpressed CD4 antigen and did not express the myeloid antigen OKM1, CD8, and antigens characteristic of immature T cells. The cells had no NK activity but did display a high helper activity. Unseparated and FACS-sorted Leu-7+ and Leu-7- Sézary cells did not respond to mitogens but were able to grow in the presence of exogenous IL-2. FACS sorted Leu-7- cells, cultured for 7 days in the presence of 20% IL-2, acquired the receptors for Leu-7. IL-2 and IFN-gamma production was studied in unseparated Leu-7+ and Leu-7- FACS-sorted Sézary cells. IL-2 production was lower than in normal cells. The addition of PHA or PHA plus TPA led to an increase in IL-2 production. Also IFN-gamma production was marked lower than in normal controls but increased after 7-day culture in exogenous IL-2. In conclusion in this case the Sézary cells may represent a neoplastic expansion of the CD3+, CD4+, CD5+, Leu-7+, Leu-11- subpopulation which is equivalent to the 2-4% of the Leu-7+ population in normal lymphocytes.