2 infusions on day 1 and day 15 rituximab infusions (1000 mg) or placebo infusions intravenous infusion of 100 mg of methylprednisolone before infusion of rituximab (or the placebo for rituximab), together with 60 mg per day of oral prednisone on days 2, 3, 16 and 17, 30 mg per day on days 4, 5, 18 and 19 and 15 mg per day on days 6 and 20