| Abstract: | Monoclonal antibodies (MoAb) directed against human terminal deoxynucleotidyl transferase (TdT) have been developed recently. The authors evaluated the reactivity of two TdT MoAb, one directed against a native site and the other against a denatured site, in bone marrow samples from patients with acute lymphoblastic leukemia (ALL) and acute myelogenous leukemia (AML). Results were correlated with the immunophenotype and compared with those obtained with an anti-TdT polyclonal antibody (PoAb). The authors found that 39 of the 45 children (87%) with ALL were positive with the anti-TdT PoAb, while only 25 of 45 (56%) were positive using MoAb. In the 41 of 45 cases of ALL for which marker studies were available, there was no relationship between immunophenotype and reactivity with the PoAb or either MoAb. Five cases of AML were studied and two were positive using the PoAb, but none showed staining with the MoAb. The authors' findings demonstrate that, although MoAb may be used to detect TdT in acute leukemia, the two MoAb used do not correlate with immunophenotype and are less sensitive than the PoAb. However, the MoAb appears to demonstrate more specificity for ALL than the PoAb, since it was not reactive in PoAb+ AML. |
