This study was designed to collect lymphocytes from patients with low levels of all blood cells (pancytopenia) for use in research. Patients participating in the study will undergo a special procedure known as lymphapheresis. During lymphapheresis blood is taken from the patient in a manner similar to blood donation. The white blood cells are selectively removed by spinning (centrifugation), and the remaining red blood cells and platelets are placed back (re-infused) into the donor s blood stream.