Increased interleukin 5 production in eosinophilic Sezary syndrome: Regulation by interferon alfa and interleukin 12

Background: Peripheral eosinophilia occurs in a small subpopulation of pati ents with cutaneous T-cell lymphoma (CTCL) and denotes a poor prognosis. Cl inical studies have suggested that the Sezary cell is a T(H)2 type helper T cell that produces cytokines that enhance the differentiation and activati on of eosinophils. Interferon alfa (IFN-alpha) and interleukin 12 are effec tive therapeutic agents for CTCL and other hematologic disorders. Objective: Our purpose was to determine the inhibitory activity of IFN-alph a and IL-12 on IL-5 production in vitro by peripheral blood mononuclear cel ls (PBMCs) obtained from patients with CTCL and eosinophilia. Methods: Suppression of IL-5 production by IFN-alpha and IL-12 was assessed by comparing IL-5 production by PBMCs from patients with Sezary syndrome a nd eosinophilia when cultured alone or in the presence of either IFN-alpha or IL-12. Results: A marked increase in IL-5 production by PBMCs from patients with S ezary syndrome and eosinophilia was observed. IL-5 production was markedly reduced when PBMCs were exposed to IFN-alpha or IL-12. Conclusion: These results suggest that IFN-alpha and perhaps IL-12 may prod uce a therapeutic response in patients with CTCL and eosinophilia through d irect suppression of IL-5 production by malignant Sezary cells.