Sex differences in the maintenance of immunologic tolerance to endogenous nucleic acid antigens and the prevention of murine lupus nephritis

Defects in antigen-specific immune tolerance in continuous B cell lines from autoimmune mice

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.

Nucleoside-specific suppression in MRL/MP +/+ mice

The induction of nucleoside-specific nonresponsiveness was further studied in the autoimmune strain MRL/MP +/+ (MRL/n). Experiments were undertaken to determine (i) whether nucleoside-conjugated spleen cells are able to induce specific nonresponsiveness to T-dependent nucleoside antigens in MRL/n mice, and (ii) whether periodic treatment with nucleoside-conjugated spleen cells would retard the development of spontaneous anti-DNA antibodies and associated indicators of autoimmunity. The results show that nonresponsiveness to nucleoside antigens is inducable in male, but not in female, MRL/n mice. Nonresponsiveness in male MRL/n was transferable and mediated by T cells. Treatment of male MRL/n mice with nucleoside-conjugated spleen cells (NSC) appeared to attenuate the progress of autoimmune symptoms in experimental animals. These results are discussed in the context of recent studies exploring the etiology of autoantibody production and the loss of self-tolerance in murine models of autoimmunity.