Methotrexate treatment in murine experimental systemic lupus erythematosus (SLE); clinical benefits associated with cytokine manipulation.

The objective of this study was to determine the effects of Methotrexate (MTX) on the development and the course of experimental murine SLE, as well as on the cytokine profile involved in the disease. SLE was induced in naive BALB/c female mice by injection of the human anti-DNA MoAb bearing a common idiotype (16/6 Id). Six weeks following immunization, when high levels of autoantibodies were demonstrated, the mice were treated with MTX (2 mg/kg once a week) for a period of 10 months. MTX treatment had no effect on 16/6 Id-induced autoantibody production. However, MTX treatment had beneficial effects on the clinical manifestations of the experimental disease (i.e. leucocyte counts, levels of protein in the urine and immune complex deposits in the kidneys). Thus, only 20% of 16/6 Id-immunized BALB/c mice that were treated with MTX had immune complex deposits in their kidneys compared with 100% of SLE-afflicted BALB/c mice that were not treated. We have observed a significant elevation in IL-1, tumour necrosis factor (TNF) and IL-10 secretion in BALB/c mice afflicted with experimental SLE. IL-2, IL-4, IL-6 and interferon-gamma (INF-gamma) levels were decreased in these mice compared with the levels detected in healthy controls. Treatment with MTX reversed the levels of all the above cytokines to normal levels observed in control mice. These studies demonstrate therapeutic effects of MTX on murine experimental SLE. The normal cytokine profile observed following treatment with MTX is suggested to play a role in the amelioration of the clinical manifestations of experimental SLE.