 This trial consists of a double-blind, placebo controlled, dose escalation part with randomization to trial treatment within each of three sequential cohorts Part A, and a parallel group part with randomization into one of four treatment arms Part B. Patients in Parts A and B will receive two infusions of either HuMax-CD20 300 mg, 700 mg, or 1000 mg or placebo and will be followed for safety, efficacy, and pharmacokinetic measurements for 24 weeks. Hereafter patients will be followed every 12 weeks until B-cells CD19 cells have returned to baseline levels. For patients in Part B, the follow-up visits at 36 and 48 weeks after initial trial treatment Follow-up Visits 1 and 2 will include additional measurements of safety and efficacy. 