Evaluation of response to rituximab in the SCID-hu WM model. Kinetics of change in human IgM paraprotein in murine serum from a representative SCID-hu mouse. (A) Serum samples were collected from mice bearing WM cells before and after rituximab therapy (25 mg/kg) every other day for a total of 3 injections. (B) Kinetics of change in IgG levels in mouse serum treated with rituximab; the IgG increase is related to the injection of rituximab (chimeric IgG). Arrows indicate the first day of treatment.