We provide direct evidence for interleukin 2 receptor (IL2R) induction by human T-cell leukemia/lymphoma virus (HTLV) in human B-cell lines. A lymphoblastoid B-cell line (LCL-Ter) was established by Epstein-Barr virus-induced transformation of peripheral blood lymphocytes derived from a healthy HTLV carrier and cloned in vitro. HTLV gp21 and/or p19 antigens were detected in eight LCL-Ter clones, all of which also expressed the IL2R antigens Tac and Hiei (defined by monoclonal antibodies). However, five other LCL-Ter clones, which were negative for the HTLV antigens, did not express the IL2R antigens. Furthermore, when the IL2R-negative B-cell line LCL-Kan, derived form a normal donor, was cocultured with HTLV-producer cells, three HTLV-carrying clones were obtained and found to constitutively express IL2R. IL2R induced by HTLV on these B-cell lines bound recombinant interleukin 2 and were similar in apparent molecular mass (approximately equal to 60 kDa) to the IL2R of peripheral blood lymphocytes stimulated with phytohemagglutinin.