A unique monoclonal antibody derived from a lupus-prone mouse with multiple bindings to autoantigens associated with rheumatic disease.

Monoclonal anti-poly(ADP-ribose) (MRP-2) was primarily a product of a hybridoma selected by binding to poly(ADP-ribose) from an autoimmune MRL/Mp-lpr/lpr (MRL/1) mouse. Detailed examination revealed that anti-poly(ADP-ribose) monoclonal IgMK antibody bound not only to left-handed Z-DNA and single-stranded (ss) DNA but also to a conformational epitope formed by histone and double-stranded (ds) DNA. A reconstitution study revealed that association of dsDNA with histone H3 plus H4 was essential for their binding to MRP-2 monoclonal antibody. MRP-2 monoclonal antibody acted as a rheumatoid factor (RF). Since some monoclonal or polyclonal human serum antibodies of rheumatoid arthritis (RA) or mixed connective tissue disease (MCTD) have been reported to recognize shared epitopes of denatured IgG and DNA-histone (nucleosomes), this MRP-2 monoclonal antibody with the similar activity derived from a lupus-prone mouse will be useful for the studies on the etiology of autoantibodies associated with RA, MCTD and systemic lupus erythematosus (SLE).