Technetium-99m labeling of human monocytes for chemotactic studies.

Although the current use of 51Cr for the evaluation of monocyte chemotaxis has yielded encouraging results, certain properties of this radionuclide leave room for improvement. Technetium-99m was evaluated as an alternative label for this purpose. A cell loss of 50% was found, but the recovered cells showed excellent viability and function. Chemotaxis was measured using a modified Boyden's chamber and a lymphocyte-derived chemotactic factor. The chemotactic properties of 99mTc-labeled human monocytes were preserved, and an excellent correlation between radioactive measurement and microscopic counting of migrating cells was observed.