The primary objective of this trial is the re-evaluation of toxicity of the new ch14.18/CHO antibody. This is ultimately followed by the secondary objectives including the determination of pharmacokinetics and immunostimulation in patients receiving ch14.18/CHO therapy. This involves particularly the determination of activation of immune effector cells and complement during and after application of ch14.18/CHO. Subsequently, we will evaluate the clinical effect of this treatment on the course of the disease.