Human T cell leukemia/lymphoma virus I infection and subsequent cloning of normal human B cells. Direct responsiveness of cloned cells to recombinant interleukin 2 by differentiation in the absence of enhanced proliferation

A human T cell leukemia/lymphoma virus (HTLV)-I-infected B cell clone expressed Tac antigen on its cell surface and responded to recombinant interleukin 2 (IL-2) by increased production of IgM without any increase in proliferation. Anti-Tac antibody completely inhibited the IL-2-induced differentiation of this HTLV-I-infected B cell clone. This study demonstrates that HTLV-I can directly infect normal mature human B cells, and that the Tac antigen, which may be induced by infection with HTLV-I, is the functional receptor for IL-2-induced B cell differentiation. The availability of such cell lines and clones should provide useful tools to delineate precisely the differentiation step in the human B cell cycle.