Idiotypic mimicry of a cell surface DNA receptor: evidence for anti-DNA antibodies being a subset of anti-anti-DNA receptor antibodies.

Anti-idiotypic anti-DNA antibodies (anti-anti-DNA) have previously been described in both patients with systemic lupus erythematosus and healthy individuals. Jerne's hypothesis predicts that such antibodies would bear a paratope reactive with non-sequence specific DNA binding proteins. Here we have explored the notion of a molecular mimicry between anti-anti-DNA antibodies and antibodies to a previously described 28-29 kD cell surface DNA binding molecule. It was shown that affinity purified anti-anti-DNA antibodies inhibit the binding of DNA to cells and that MoAb to the 28-29 kD receptor react with anti-DNA antibodies. These findings indicate that a subset of anti-anti-DNA antibodies are idiotypically related to antibodies reactive with a cell surface DNA binding molecule. It is hypothesized that anti-DNA antibodies may arise when a convergence of genetic and environmental influences favours an unrestrained anti-idiotypic response to cell surface DNA binding molecule(s).

Autoimmunity to a 28-30 kD cell membrane DNA binding protein: occurrence in selected sera from patients with SLE and mixed connective tissue disease (MCTD).

Previous experiments have established the presence of a 30-kD DNA binding protein on the surface of human leukocytes. Herein we report that selected sera from patients with systemic lupus erythematosus (SLE) and MCTD are reactive with a 28-30 kD protein on immunoblots of peripheral blood mononuclear cells (PBMC) cell membrane preparations; the reactivity is abolished by prior incubation of the blot with DNA. Antibodies eluted from the 28-30 kD strip inhibited the binding of 3H. DNA to human PBMC. An immunomatrix of 28-30 kD reactive immunoglobulins was able to extract a 29-kD DNA binding protein from a PBMC cell membrane preparation. Flow cytometry experiments confirmed the cell surface IgG reactivity of sera with T lymphocytes. Additional experiments indicated that cell surface IgG binding was not due to antibodies binding to cell surface DNA, DNA anti-DNA immune complexes reacting with a DNA binding protein, anti-histone antibodies or anti-Sm antibodies. It is hypothesized that this autoimmune response could be one component of an idiotypic network involving anti-DNA antibodies.

DNA receptor dysfunction in systemic lupus erythematosus and kindred disorders. Induction by anti-DNA antibodies, antihistone antibodies, and antireceptor antibodies.

The ability of sera from patients with SLE and similar connective tissue diseases to induce dysfunction of the receptor for DNA was studied. All SLE and MCTD sera studied resulted in marked inhibition of DNA receptor binding. Furthermore, the sera from a subgroup of patients with other rheumatic diseases and a surprisingly high percentage of asymptomatic relatives of SLE patients exhibited a similar effect. The humoral factors causing this defect were shown to be of at least three reactivities: (a) antibodies to DNA, (b) antibodies to histones, and (c) antibodies to the DNA receptor itself. The reactivity of anti-DNA and antihistone antibodies is dependent upon intact cell-surface DNA, and reconstitution experiments suggest that antihistone antibodies are reactive with histones complexed to this DNA, which in turn is bound to the DNA receptor. Cells with an antibody-induced DNA receptor defect are unable to bind DNA; the subsequent inability to degrade DNA may have important consequences in diseases such as SLE in which DNA-anti-DNA immune complexes are of pathogenetic significance.