Leukocyte labeling in plasma made simple and efficient: Preparation and evaluation

Over the past few years the use of In-111 leukocytes (In-111-L) for abscess localization has become increasingly popular. Using less toxic Mercaptopyridine-N-oxide or its Na-salt (Merc, LD/sub 50/ 340 mg/kg b.w.) rather than oxine (LD/sub 50/ 88.8 mg/kg b.w.), In-111-L could be prepared either in salt balance media or preferably by a kit procedure in plasma. In the plasma preparation L concentrated in 0.5 ml plasma are added to 25 ..mu..g dry Merc and subsequently incubated at an ambient temperature for 20 minutes with a weak chelate of In-111 either dry or in solution. Greater than 90/sup 0/ labeling efficiency is achieved which compared favorably to 10 ..mu..g and 50 ..mu..g each of oxine and tropolone. Phagocytic ability of 10 million L exposed to up to 200 ..mu..g Merc remained unaffected. In-111-L and Ga-67 citrate were given to abscess bearing dogs and abscess/blood (24 hr.) ratios of 75 and 12 respectively were achieved. Those were similar to those obtained with In-111-oxine labeled L (75.2 vs. 75.8). Abscess/liver and abscess/spleen ratios obtained with In-111-merc labeled L (14.6 and 4.2 respectively) were more favorable than those obtained with In-111-oxine labeled L (4.2d and 1.8 respectively). These indicated that less quantity of Lmore » labeled with In-111-Merc was deposited in these organs. Furthermore, L labeled with In-111-Merc cleared more rapidly from human lungs than L labeled with In-111-oxine. Data indicate that use of Merc permits efficient L labeling in plasma, provides a kit method, and preserves L physiologic function.« less