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Ultrastructural study of leukemic cell phagocytosis using the myeloperoxidase reaction
Abstract:
The phagocytosis (in the absence of serum factors) of zymosan particles by peripheral leukocytes isolated from ten patients with acute leukemia (AMbL, AMoL, AMML, AUL, ALL and CML-BC) was studied at the electron microscope. An evident phagocytic activity was observed only in the cells in which cytochemical and ultrastructural features suggested that the blast elements belonged to the monocytic series. However, no phagocytosis by unclassifiable leukemic blasts was observed, even though they had some submicroscopic characteristics of the monocytic series. These findings suggest that phagocytic capacity develops during the course of cell differentiation, becoming striking only when the blast cell acquires the ultrastructural features of the pro-monocytic stage. Using the myeloperoxidase reaction, this study also demonstrates a morphological alteration in the degranulation process after the ingestion of zymosan particles in both the blasts and the mature PMN cells of leukemic patients. This defect could be related to the susceptibility to severe infections usually found in subjects with hematological malignancies.
Insights
Phagocytosis in leukemia patients is limited to monocytic cells, indicating impaired immune function. This study reveals defects in degranulation, potentially explaining infection susceptibility in hematologic malignancies.
Area of Science:
- Hematology
- Immunology
- Cell Biology
Background:
- Leukemia involves abnormal white blood cell proliferation.
- Leukemic cells often exhibit impaired immune functions.
- Phagocytosis is a critical immune response by leukocytes.
Purpose of the Study:
- To investigate phagocytic activity in peripheral leukocytes from leukemia patients.
- To determine the role of cell differentiation in phagocytosis in leukemia.
- To examine degranulation defects in leukemic cells.
Main Methods:
- Electron microscopy was used to study phagocytosis of zymosan particles.
- Peripheral leukocytes from ten acute leukemia patients were analyzed.
- Myeloperoxidase reaction was employed to assess degranulation.
Main Results:
- Phagocytic activity was evident only in leukemic cells with monocytic features.
- Unclassifiable leukemic blasts showed no phagocytosis despite some monocytic characteristics.
- Morphological alterations in degranulation were observed in both leukemic blasts and mature PMN cells.
Conclusions:
- Phagocytic capacity develops during leukemic cell differentiation, becoming prominent at the pro-monocytic stage.
- Defective degranulation in leukemic leukocytes may contribute to increased infection susceptibility.
- Understanding these defects is crucial for managing hematologic malignancies.