TdT-positive and TdT-negative human leukemic cells: specific density and morphology

Area of Science:

• Hematology
• Oncology
• Cell Biology

Background:

• Terminal deoxynucleotidyl transferase (TdT) is a key enzyme in lymphoid development.
• TdT expression is a marker in certain leukemias, including acute lymphoblastic leukemia (ALL) and chronic myeloid leukemia (CML).
• Understanding TdT+ cell distribution can provide insights into leukemia cell maturation and heterogeneity.

Purpose of the Study:

• To investigate the distribution and density characteristics of TdT+ cells in peripheral blood from ALL and CML patients.
• To explore potential correlations between cell density, TdT expression, and cell maturation in these leukemic conditions.

Main Methods:

• Peripheral blood cells from ALL (E- and D+ SIg-) and CML in blastic crisis patients were analyzed.
• Cells were separated into fractions using discontinuous albumin density gradient centrifugation (Dicke's method).
• Terminal deoxynucleotidyl transferase (TdT) activity was assayed in each fraction.
• Cell morphology was examined using electron microscopy for correlation with marker characterization.

Main Results:

• TdT+ cells showed variable density distribution in E- ALL and CML-BC, suggesting differences in cell maturation.
• In some cases, the majority of leukemic blasts were found in TdT-negative or weakly positive fractions.
• Most E- ALL and CML-BC patients had TdT+ cells predominantly in low-density fractions.
• All E+ ALL patients exhibited high-density TdT+ cells.

Conclusions:

• Cellular density and TdT expression levels are heterogeneous in ALL and CML-BC.
• The findings suggest that TdT+ cell density can be an indicator of cell maturation status in these leukemias.
• Electron microscopy revealed correlations between cell morphology and TdT marker characteristics.