In the study of BPDCN patients it was of fundamental importance the discovery by Chaperot and coworkers about the expression of IL-3Rα chain on CD4+/CD56+ leukemic cells: upon in vitro incubation with IL-3 the leukemic cells undergo a partial maturation and became a powerful inducer of naïve CD4+ T cell proliferation [23]. This evidence concerns the gene CD4 and CD4+/CD56+ hematodermic neoplasm.