Blood cell labeling with 99mTc: progress and perspectives.

Blood cell labeling with 99mTc has progressed through various developmental phases. In the case of red cell labeling, the science seems to have matured sufficiently, although minor refinements in the procedures will no doubt continue to be made. During the last 3 to 5 years, there has been a resurgence of interest in labeling leukocytes and platelets with 99mTc. As a result of these efforts, the techniques for these cell types appear to be developing slowly, having finally come out of their infancy. Progress in these directions over the last 3 1/2 years is summarized and discussed in this article. Emerging techniques that offer the promise of combining simplicity and convenience with reliable and reproducible data are highlighted. Mechanisms involved in the various labeling approaches, if studied and understood, are included. Recent efforts on cell labeling with 99mTc using the monoclonal antibody approach are summarized. Although results in this area are quite preliminary, the monoclonal antibody approach holds the greatest promise for labeling leukocytes and platelets in vivo, and thus overcoming the biggest drawback of current techniques, ie, cell separation and handling before labeling. This is a US government work. There are no restrictions on its use.