In vitro studies of leukocyte labeling with technetium-99m

A method for labeling leukocytes in vitro with 99mTc is described. Separated leukocytes are incubated with 99mTc, followed by reduction with stannous chloride and washing with acid citrate dextrose solution. Maximum labeling occurs after at least 5 min incubation with pertechnetate, followed by at least 10 min incubation with stannous chloride. Labeling is similar at room temperature and at 37 degrees C. The labeled leukocytes are viable, and reutilization of label does not occur in vitro. In acid conditions (pH 5.2), the elution of 99mTc from leukocytes is comparable with that of 32P-diisopropylfluorophosphate, but 99mTc elution is greater at pH 7.2--7.4. Neutrophils label more heavily with 99mTc than do monocytes, lymphocytes, erythrocytes, or platelets.