Basic studies on 111In chelate compounds for WBC labeling

Five 111In chelate compounds were compared as WBC labeling agents. Among those, 111In-ascorbylaplmitate achieved the highest labeling efficiency. The leucocytes labeled by this compound, however, failed to visualize the abscess. 111In-acetylacetone and 111In-oxine, which both gave 10 - 30% labeling efficiency against --4 x 105 of leucocytes, showed significant difference in stability of the label, when the leucocytes labeled with each compound were incubated with plasma at 37. C. While 50% of 111In-oxine molecules remained in the cells after washing, on the other hand 90% of 111In-acetylacetone complexes were released into the plasma. As expected from the result, scintigraphy using the 111In-leucocytes labeled with 111In-acetylacetone showed high background 111In level, although the abscess was visualized. WBC labeling with 111In+ in indium chloride solution resulted in unexpectedly high labeling efficiency, 16 - 36%. However, release of 111In was also high, 80%, when incubated with plasma. (author)