If you are found eligible to take part in this study, you will receive treatment as an outpatient. You will receive GM-CSF 3 times a week for 4 weeks through a vein, starting the day before you receive the administration of rituximab. You will receive rituximab over 4 to 8 hours through a vein, once weekly for 4 weeks. You will also get a boost of NK cells from the same donor from whom you received your original transplant. These cells will be infused through a vein (over 30 to 60 minutes) after the 4th dose of rituximab. If you are receiving a cell infusion from somebody who you are not related to, the infusion may have to be done later if cells were not available as scheduled.