Dichotomic effects of IFN-gamma on the development of systemic lupus erythematosus-like syndrome in MRL-lpr/lpr mice

Systemic lupus erythematosus (SLE)-prone female MRL-lpr/lpr (MRL-lpr) mice were treated with mouse or rat IFN-gamma under different experimental condi tions, both prophylactically in 6- to 8-week-old animals and therapeuticall y in 12- to 18-week-old SLE-affected mice. It was found that IFN-gamma hete rogeneously modulated the course of the disease in MRL-lpr-mice. When admin istered prophylactically, IFN-gamma favorably modulated the histological, s erological and clinical signs of the disease. Relative to untreated or PBS- treated control animals, the MRL-lpr mice which received IFN-gamma were vir tually free of inflammatory infiltration of the kidneys and the lungs, had lower levels of azotemia with reduction of both circulating IgG1 IgG2a and IgG3 and anti-double strand (ds) and single strand (ss) DNA antibodies, mil der skin vasculitis, significantly reduced enlargement of their lymph nodes and lower weight of the spleens. IFN-gamma also lowered the rate of mortal ity of MRL-lpr mice. In contrast to these findings, therapeutically adminis tered IFN-gamma worsened the course of the disease in MRL-lpr mice, which e xhibited increased proteinuria, higher levels of IgG2a and IgG3 and anti-ds and -ss DNA antibodies, more aggressive nephritis and died at an earlier a ge than PBS-treated control mice. The dichotomic effect of IFN-gamma on dis ease manifestation in MRL-lpr mice offers new insights into the complex rol e of this cytokine in the regulation of systemic autoimmunity such as SLE.