Immunoenzymatical Staining for Terminal Deoxynucleotidyl Transferase

To the Editor: Terminal deoxynucleotidyl transferase (TdT), an enzyme that catalyzes the addition of deoxynucleotides to the 3'-OH end of oligonucleotides or polydeoxynucleotides, has become an important marker for the classification of acute and chronic leukemias and certain types of lymphoma, and serves as a marker for lymphoid-cell differentiation. 1 Originally determined by an enzyme-activity assay, TdT can now also be detected immunocytologically by indirect immunofluorescence (IF). The enzyme assay is time-consuming and technically demanding. The IF assay has overcome these problems but still depends on special equipment and has the disadvantage of instability of the reagent product after a certain . . .