Dissociation between coupled lymphocyte phenotypic and functional properties in Sézary cells

Neoplastic lymphocytes derived from three patients suffering from Sézary syndrome were studied by immunologic and functional analysis. Populations of neoplastic T cells (greater than 90% as judged by morphologic criteria) were isolated from involved lymph nodes. Sézary cells expressed T3 and T4 but not T8 membrane antigens displaying the same phenotypic pattern of normal helper/inducer T cells. On the contrary the mitogenic response of Sézary cells to phytohemagglutinin appears lower than that exhibited by peripheral T lymphocytes. The amounts of interleukin 2 produced by Sézary cells were examined in two out of three cases: in one case it appeared similar to that produced by peripheral blood lymphocytes while in the other it was about one-half lower. Furthermore the capacity of dexamethasone at 10(-7) M in inhibiting T-cell mitogenesis was comparatively analyzed in T lymphocytes from Sézary lymph nodes, reactive lymph nodes, normal peripheral blood, and normal thymus. It was clearly apparent that the mitogenesis of Sézary cells, unlike that of peripheral blood lymphocytes and that of lymphocytes from reactive lymph nodes, was strongly inhibited by dexamethasone (greater than 70%); such inhibition was very similar to that observed for normal thymocytes. Taken together these results suggest that despite the phenotypic pattern of mature helper/inducer T cells, Sézary lymphocytes are functionally a less mature T-cell type.