Cross-reacting antibodies to human T cell leukemia virus-I and -II in Japanese patients with hairy cell leukemia.

: Sera from 11 Japanese patients with hairy cell leukemia and 4B122, an anti-hairy cell serum produced by the authors, were surveyed by Western blot analyses for cross-reacting antibodies to human T cell leukemia virus (HTLV)-I and -II virions released, respectively, from Lma-66 and Mo-T cell lines. Sera from the majority of the patients showed positive reactions with p15, p19, and/or p24 of HTLV-I and with p21 and/or p22 or HTLV-II. 4B122 was weakly cross-reactive with HTLV-II but not with HTLV-I. These results militate against the involvement of HTLV-I or -II but may implicate a role by a cross-reacting, previously unrecognized retrovirus in the pathogenesis of hairy cell leukemia in Japanese patients.