Labeling of mixed leukocytes with (99m)Tc-HMPAO causes severe chromosomal aberrations in lymphocytes.

Unlabelled: 99mTc-d,1-hexamethylpropyleneamine oxime (HMPAO) is widely used as a labeling agent for leukocytes in the diagnosis of inflammatory or infectious foci. Cytotoxicity studies have indicated that intracellular labeling of leukocytes with (111)In compounds may have severe detrimental effects on the cells.

Methods: In this study, the radiotoxic effects on mixed lymphocytes after labeling with (99m)Tc-HMPAO was investigated using the cytokinesis-blocked micronucleus assay and chromosomal aberration assay.

Results: Whereas negligible numbers of chromosome abnormalities were noted in unlabeled lymphocytes, the labeled lymphocytes showed multiple aberrations of various types, including dicentric, tricentric, and fivecentric chromosomes; centric rings; chromosome and chromatid type breaks; and acentric fragments.

Conclusion: Heavily aberrant lymphocytes are seen in (99m)Tc-HMPAO-labeled mixed leukocytes after routine clinical procedures. It is unlikely, however, that this would cause detrimental effects, such as lymphoid malignancy, as these cells would normally be eliminated through apoptosis or phagocytosis.