Indeed, the use of the first described anti-HBZ mAb, 4D4-F3, has allowed us to better characterize the expression and the localization of HBZ molecules in chronically infected HTLV-1 positive cells as well as in cells from ATL patients, either as an established cell line (ATL-2s), or as fresh tumor cells from patient PMBC. The gene discussed is HBZ; the disease is neoplasm.