Interstitial pneumonitis in autoimmune MRLlpr mice and its treatment with cyclosporin A

Age-associated changes of anti-double-stranded (ds) DNA antibodies, anti-single-stranded (ss) DNA antibodies, and serum immune complex concentrations were studied in MRLlpr mice. All anti-ds DNA antibodies, anti-ss DNA antibodies, and immune complexes began to be detected in the sera of MRLlpr mice aged 8 to 13 weeks and increased remarkably after 17 weeks of age. Almost no pathological findings were observed histologically in the lungs of MRLlpr mice aged 8 weeks but interstitial pneumonitis became evident at 14 weeks of age. Peribronchial and perivascular lymphocyte infiltrations were seen in the lungs of 14-week-old MRLlpr mice and became more severe at 21 weeks of age. Oral administration of cyclosporin A to 15-week-old MRLlpr mice markedly prolonged their life span. The lungs of 44-week-old MRLlpr mice given cyclosporin A showed few pathological findings except for minimal perivascular lymphocyte infiltration.