An assay for terminal deoxynucleotidyl transferase in leukocytes and bone marrow

A modified technic for the assay of terminal transferase activity in leukocytes and bone marrow is presented. 3H-deoxyadenosine-5' -triphosphate serves as nucleotide donor and (dA)10 as primer. The reaction product is collected as a trichloroacetic acid precipitate, which is dissolved for radioactive quantitation. All reagents are commercially available, and the procedure has been designed to minimize cost and to provide low blank values. Excellent linearity between enzymatic concentration and activity and between time and activity is observed. Because the assay is carried out at conditions approaching the optimum for the enzyme, the measured activities are more than ten times those observed with previous methods.