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Guide And Atlas For The Detection Of Minimal Residual Disease In AML

Terminal Transferase Detection (TdT) in AML

TdT, previously considered associated with early lymphoid cells, is now seen as a marker of immaturity.[4]


Immunofluorescence showing TdT. This view demonstrates double-staining of the myeloblasts, which stain red on the surface by an antibody to the myeloid antigen Cdw65 with TdT. They stain green in the nucleus by an anti-TdT antibody.[4]


Flow cytometric determination. These cells double-stain with HLA-DR, which is a marker of immature cells (contour plot A). After treatment and achievement of a clinical and morphological remission, less than 1% of HLA-DR +/TdT+ blast cells are still detectable by flow cytometry, where normally no TdT+ cells should be seen (contour plot B).[4]

MRD-based TdT shown by RNAse protection assay. The autoradiograph showing the molecular technique, RNAse protection assay, demonstrates the high abundance of a 0.6kb TdT-specific RNA transcript at presentation (lane B), comparable with TdT expression in a positive control cell line (lane A), and in agreement with the great expression of TdT detected by immunostaining. Lane C shows a markedly lower but clearly detectable abundance of the TdT transcript in the patientís RNA from peripheral blood at the time of remission, which is in agreement with the small number of TdT+ cells seen at that time by flow cytometry.[4]

The equivalent abundance of actin transcripts in all three samples (bottom) demonstrates that differences in the TdT signal are not due to differences in total RNA analyzed.[4]

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