ARM B: Placebo by IV infusion at study entry followed by placebo by IV infusion at weeks 4 and 8, and THEN TCZ, 4 mg/Kg (not to exceed 400 mg) by IV infusion over 60 minutes once at week 24, followed by TCZ, 8 mg/Kg (not to exceed 800 mg) by IV infusion over 60 minutes at weeks 24 and 28.