Antigen-Binding Diversity of Human Hybridoma Autoantibodies Derived from Splenocytes of Patients with SLE

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Abstract
The antigen-binding specificity of human hybridoma-derived monoclonal autoantibodies (mAb) was analysed with mAbs derived from the spleens of two patients with active systemic lupus erythematosus (SLE). From one patient 72 mAbs (RSP clones) and from the other 173 mAbs (RT clones) were obtained. The binding specificity of these mAbs was analysed by solid- and fluid-phase ELISA against the autoantigens ssDNA, dsDNA, cardiolipin, SmRNP, histones, Sm-D and SS-B (La) synthetic peptides, and foreign antigens including bacterial polysaccharides. In addition, antinuclear antibody activity and anti-dsDNA binding were con firmed by fluorescence staining methods. Reflecting the patient's serological profile, none of the antibodies from the RSP clones reacted with ssDNA or dsDNA but 12 reacted with car diolipin. In addition, three mAbs reacted with H4, five with U 1 RNP, two with Sm-D peptides and 12 with SS-B peptides. In contrast, from the RT fusion, nine mAbs reacted with ssDNA, HI and SS-B peptides, seven with cardiolipin, four with dsDNA, two with Sm-D peptides and one each with H2A, H3 and H4. In many cases one mAb showed reactivity with more than one antigen: for example, mAb RT 72 binds to ssDNA, dsDNA, cardiolipin, H1, H4 and an Sm-D peptide; RT 6 binds to H1, SmRNP and ubiquitinated histone H2A. However, none of the antibodies showed 'across the board' polyreactivity; indeed, the selectivity of the reactions was notable and marked variation in antibody affinity was recorded. Eight of the mAbs bound to Salmonella typhimurium and two to the Klebsiella polysaccharide K-30. This report con firms the diversity in the antigen-binding pattern and polyreactivity of autoantibodies derived from SLE patients and supports the notion that antibodies to autoantigens can also bind to foreign antigens. It also suggests that the antigen-binding profiles of human hybridoma- derived antibodies reflect the range of antibodies present in the serum of individual patients.

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