[Systemic lupus erythematosus and nucleosome]

Abstract

The property of nucleosome in systemic lupus erythematosus (SLE) is reviewed. Nucleosome, complex of histone and DNA, is thought to have a pivotal role in pathogenesis of SLE. It is formed during apoptosis that is increased in peripheral lymphocytes of SLE. The concentration of nucleosome is elevated in SLE, probably related with disease activity. Nucleosome is speculated that the clearance from peripheral blood is decreased and that is modified by viral infection to become more immunogenic. Anti-nucleosome antibody is highly positive in majority of SLE, and is very specific for SLE except scleroderma and mixed connective tissue disease. This antibody is thought as a diagnostic marker and probably an activity marker for SLE. Anti-nucleosome antibody forms immune complex with nucleosome. As histone has strong positive charge, it is demonstrated that this nucleosome/anti-nucleosome complex is bound to negatively charged heparan sulfate of glomerular basement membrane in kidney. Then, complements bind to this antibody to generate lupus glomerulonephritis. Although main site of apoptosis in SLE is considered as lymphocytes, we experienced a case with SLE who had liver dysfunction with elevated soluble Fas ligand (sFasL) and apoptosis in her hepatocytes in the active stage of SLE. We measured serum sFasL, and found the relation of sFasL and liver involvement in active SLE. As major source of nucleosome should be apoptosis of lymphocytes in SLE, hepatocytes could be another candidate of apoptosis in some SLE.