Sézary T-cell-activating factor induces functional interleukin 2 receptors on T-cells derived from patients with...

Sézary syndrome is the leukemic form of cutaneous T-cell lymphoma characterized by circulating neoplastic CD4+ T-cells. Although peripheral blood mononuclear cells from patients with Sézary syndrome have been shown to respond poorly to mitogens, we found that mitogen-activated peripheral blood mononuclear cells from four of five patients with Sézary syndrome produce a 28 kDa protein termed Sézary T-cell activating factor (SAF). SAF renders nonproliferating "resting" T-cells from leukemic patients or healthy donors responsive to interleukin 2 in the absence of a costimulator. We demonstrate that SAF induces functional, high-affinity interleukin 2 receptors on T-cells from Sézary syndrome patients and provide evidence that SAF may be a novel cytokine.