Lupus erythematosus cell formation by a monoclonal antibody derived from an autoimmune MRL/Mp-lpr/lpr mouse

An MRP-2 monoclonal antibody (MoAb) was primarily a product of hybridoma selected by binding to poly(ADP-ribose) from a lupus prone MRL/Mp-lpr/lpr (MRL/l) mouse, and was shown to cross-react with single-stranded (ss) DNA. Detailed examination revealed that MRP-2 MoAb bound to a conformational epitope formed between double-stranded (ds) DNA and total histone: both H3 and H4 were essential for the formation of this conformational epitope with dsDNA. Because of this characteristic of the MoAb, its ability to induce lupus erythematosus (LE) cells was examined in an indirect LE test with peripheral blood of MRL/Mp-+/+ (MRL/n) mice, which develop a mild form of lupus after the age of one year. MRP-2 MoAb was found to induce hematoxylin bodies, LE rosettes and LE cells, but a direct LE test using MRL/n mouse blood did not induce LE cell phenomena. This is the first demonstration of induction of LE cells by a MoAb that binds to dsDNA-histone complexes.