Background:||Standard therapy is ill-defined for patients with systemic lupus erythematosus (SLE) suffering from the membraneous form of Lupus nephritis (WHO class V). Therapeutic options used at present include azathioprine.||In a small, open label safety study, patients with lupus nephritis, including patients with membraneous lupus nephritis, have experienced a long-lasting therapeutic response, with sustained reduction in proteinuria, following a 10 weeks course of 4 infusions of infliximab in combination with azathioprine. This short course appeared safe with regard to SLE activity, despite increases in autoantibody levels.||Study hypothesis:||The combination of four infusions of infliximab (5 mg/kg of body weight)administered at weeks 0, 2,6, and 10, with azathioprine will be faster than azathioprine alone in reducing proteinuria to less than 1.5 g/day in patients with active lupus nephritis WHO class V (proteinuria > 3g/day).|This combination therapy will show a tolerable safety profile with regard to SLE activity and infections.