TdTpositive

TdTpositive refers to cells or samples that exhibit the presence of terminal deoxynucleotidyl transferase (TdT) enzyme activity. TdT is a DNA polymerase that adds nucleotides to the 3' end of a DNA strand without the need for a template. It is primarily expressed in lymphoid progenitor cells in the bone marrow and thymus. The presence of TdT is a significant marker during the early stages of lymphocyte development.

In the context of leukemia, TdT positivity is a characteristic feature of acute lymphoblastic leukemia (ALL), particularly B-cell ALL and T-cell ALL. The enzyme is involved in the V(D)J recombination process, which is essential for generating diversity in antigen receptors on lymphocytes. In leukemic cells, TdT is often aberrantly expressed, contributing to the uncontrolled proliferation of immature lymphoid cells. Therefore, TdT testing is a crucial diagnostic tool for classifying and monitoring ALL.

Beyond hematological malignancies, TdT activity can also be detected in other cell types, though typically at much lower levels or in specific physiological conditions. However, its strong association with lymphoid progenitor cells makes its presence a key indicator in the study of hematopoiesis and lymphopoiesis. The detection of TdT is usually performed using immunocytochemistry or flow cytometry techniques.