Evaluation of methods of detecting terminal deoxynucleotidyl transferase in human hematologic malignancies. Comparison of immunofluorescence and enzymatic assays

Terminal deoxynucleotidyl transferase-positive cells in human tonsils

To study the possible cellular origin of recently recognized indolent terminal deoxynucleotidyl transferase (TdT)-positive T-lymphoblastic proliferations of the tonsils and oropharynx, we studied normal human tonsils for the presence of TdT-positive cells. TdT-positive cells were readily demonstrated in the tonsils from 15 children and adults by immunohistochemical staining. TdT-positive cells were distributed in discrete foci at the periphery of lobules of lymphoid tissue and adjacent to fibrous septa and had the morphologic features of small to medium-sized lymphocytes. Double-antibody staining indicated the TdT-positive cells had the phenotype of uncommitted early lymphoid precursors (CD3-, CD79a-, CD10-). Foci of TdT-positive cells were not identified in 6 reactive lymph nodes studied as controls. These studies indicate that tonsils, like bone marrow and thymus, are sites of lymphopoiesis. The presence of TdT-positive precursor cells in human tonsils may be a factor in the pathogenesis of recently described indolent T-lymphoblastic proliferations involving the tonsils and oropharynx. The presence of TdT-positive cells in human tonsils should not be misinterpreted as evidence of lymphoblastic lymphoma or leukemia.

Evaluation of a new enzyme-linked immunoassay for terminal deoxynucleotidyl transferase in haematologic malignancies

We have evaluated a new solid phase enzyme immunoassay (EIA) for detection of terminal deoxynucleotidyl transferase (TDT). The EIA is greater than 100 times more sensitive than previously used tests for enzyme activity. In 284 clinical specimens of human peripheral blood and bone marrow, the EIA detected TdT antigen in 97% of peripheral blood and 100% of bone marrow samples that were positive for enzymatic activity. The excellent sensitivity and specificity of this new test suggests that it can be used in clinical situations where quantitative TdT measurements are desired.

Affinity purification and refined structural characterization of terminal deoxynucleotidyltransferase

A total of 56 stable murine hybridoma monoclones that produce homogeneous antibodies against human or calf terminal deoxynucleotidyltransferase have been established. All of the antibodies exhibited specific binding to various Mr forms of terminal transferase and eight possessed neutralizing activity. Results are presented that permitted characterization of ten of these antibodies with respect to their immunoglobulin class, their recognition of calf or human terminal-transferase Mr species by immunoblotting techniques and their recognition of distinct antigenic sites. Terminal transferase was purified in a single step by using an immunoaffinity column constructed with a monoclonal antibody exhibiting a high binding affinity for the enzyme. Single monoclonal antibodies were also used to bind selectively to terminal-transferase antigen in tissue slices and individual cells.

Immunologic, morphologic and chromosomal characterization of a cell line (TC78) established from a child with acute lymphoblastic leukemia

We characterized a cell line established from bone marrow cells from a child with acute lymphoblastic leukemia. This cell line, TC78, had lymphoblastic morphology and was cytoplasmic peroxidase and esterase negative. The cells did not have T- or B-cell properties such as E- or EAC-rosette forming ability, reactivity with monoclonal T-cell or B2 antibodies, or immunoglobulin synthesis. We concluded that TC78 was a pre-pre B-cell line based on the following monoclonal antibody staining pattern: BA-1+, BA-2+, cALLa+, Ia+, 2H7+ and OKB2+. Growth in 'Dickie' culture and reactivity with 1G10 myeloid antibody suggested coexpression of lymphoid and myeloid characteristics. However, 1G10 expression proved dependent on culture conditions, illustrating one caveat in application of monoclonal antibodies in lineage determination.

Demonstration of terminal deoxynucleotidyl transferase in single cells by indirect immunofluorescence. II. An examination of specificity

Advantages in the use of indirect immunofluorescence for the identification of terminal transferase (TdT) in single cells may be offset by lack of specificity, as compared to the biochemical assay of the enzyme, especially in analyses of lymphocyte populations. False positive results were obtained in 15/15 tonsillectomy samples and in 9/27 specimens from children with acute lymphoblastic leukemia in remission, perhaps due to antihuman lymphocyte activity in the rabbit heteroantisera which are used in the indirect immunofluorescence technique. This phenomenon may be more pronounced in 'activated' normal lymphocytes. Such reactions are not due to antibodies directed against adenovirus, papovavirus or EB virus antigens, although these are common constitutents of human tonsillar cells. Additional problems with TdT heteroantisera may result from immunization with non-TdT determinants in calf thymus extracts, as was manifest in human non-lymphoid (KB) cells cultured in fetal bovine serum. These difficulties will be overcome only by production of a monoclonal antibody using human TdT as the antigen.