The purpose of this study is to determine the optimum conditions for obtaining a leukocyte button which most effectively will be subsequently labelled with 111In oxine. As in all radiopharmaceuticals, the highest radiopharmaceutical purity, or the fraction of total radioactivity in the desired radiopharmaceutical form (111In oxine leukocyte), the better the product. Many 111In ocine labelled leukocytes are contaminated by labelled platelets, red cells, and proteins, resulting in a “dirty” product. But with careful leukocyte culturing, sedimentation, centrifugation, and labelling, as demonstrated by this study, a highly desirable, pure radiopharmaceutical can be made. In an attempt to further purify the leukocyte button beyond centrifugation, hypotonic red cell lysing and its effect on leukocyte viability will be studied. The optimum incubation time will be determined by examining the leukocyte and red cell elution profiles at different incubation times. And, 0.9% saline washes of plasma and proteins from the leukocytes will be varied by both volume and number to determine if extra washes will optimize the labelling efficiency.