B cell hyperactivity and resistance to tolerance induction are well-recognized immunologic abnormalities associated with both human and murine models of systemic lupus erythematosus. Studies evaluating the role of B cells in these defects have been complicated by the difficulties of consistently isolating large numbers of B cells from T cells and other host-derived regulatory factors. We have recently developed continuous cell lines of B lymphocytes with a high degree of specificity for the antigen dinitrophenyl (DNP) from both New Zealand black times New Zealand white F1 hybrid (BWF1) and BALB/c mice, and we used them to study intrinsic B cell defects in autoimmunity. We found that the kinetics of the immune response to the antigen DNP-Ficoll of both the BWF1 and BALB/c B cell lines are not different. In addition, the BWF1 cell lines, like the BALB/c cell lines and normal B cells, require nonspecific T cell-derived factors as well as antigen to produce an immune response. Tolerance was tested in the BWF1 B cells by preincubating them with DNP-murine IgG2a (MGG), which can induce tolerance in BALB/c cell line lymphocytes. The BWF1 B cell lines were resistant to tolerance induction by DNP-MGG and required 50-fold higher dose of DNP-MGG than BALB/c cell lines for suppression. They were also relatively resistant to tolerance with trinitrophenyl-d-glutamyl lysine. Thus, DNP-specific B cells from autoimmune mice have an inherent defect in tolerance induction.