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Fast and Specific Assessment of the Halogenating Peroxidase Activity in Leukocyte-enriched Blood Samples
Published on: July 28, 2016
Myeloperoxidase immunoreactivity in adult acute lymphoblastic leukemia
D A Arber1, D S Snyder, M Fine
1Division of Pathology, City of Hope National Medical Center, 1500 E Duarte Rd, Duarte, CA 91010, USA.
Abstract:
To evaluate the frequency and significance of myeloperoxidase positivity in adult acute lymphoblastic leukemia (ALL), bone marrow biopsy material from 82 adults with ALL was evaluated with a polyclonal myeloperoxidase (pMPO) antibody. Nineteen cases (23%) demonstrated evidence of pMPO immunoreactivity. Positive cases were precursor B-cell lineage, and CD13 or CD15 expression was more frequent than in the pMPO-negative cases. A subset of pMPO-positive cases studied with a monoclonal MPO antibody was negative. Western blot analysis using the pMPO antibody showed the expected 55-kd band for myeloperoxidase in pMPO-positive and pMPO-negative ALLs, suggesting a lack of specificity of this antibody in ALL. Forty-two percent (8/19) of the pMPO-positive ALL cases demonstrated evidence of t(9;22) by either karyotype or polymerase chain reaction analysis. The pMPO-positive ALLs had a lower frequency of extramedullary disease than the pMPO-negative group and a trend toward improved overall survival compared with the pMPO-negative group. Immunoreactivity with pMPO in adult ALL may lead to an incorrect interpretation of biphenotypic acute leukemia using a recently described scoring system, and a revision to that scoring system is proposed to accommodate pMPO-positive ALL.
Insights
Myeloperoxidase (MPO) positivity was found in 23% of adult acute lymphoblastic leukemia (ALL) cases. This finding may impact diagnosis and prognosis, suggesting a need to revise current scoring systems for ALL.
Area of Science:
- Hematology
- Oncology
- Immunohistochemistry
Background:
- Myeloperoxidase (MPO) is an enzyme typically associated with myeloid lineages.
- Its expression in acute lymphoblastic leukemia (ALL) can complicate lineage determination and diagnostic classification.
Purpose of the Study:
- To determine the frequency and clinical significance of MPO positivity in adult ALL.
- To assess the specificity of polyclonal MPO (pMPO) antibody in ALL.
- To evaluate the impact of pMPO positivity on ALL characteristics and outcomes.
Main Methods:
- Bone marrow biopsy samples from 82 adult ALL patients were analyzed using a polyclonal MPO (pMPO) antibody.
- Immunoreactivity was assessed, and positive cases were further evaluated for B-cell lineage markers (CD13, CD15).
- Western blot analysis and genetic testing (karyotype, PCR for t(9;22)) were performed.
Main Results:
- Twenty-three percent (19/82) of adult ALL cases showed pMPO immunoreactivity.
- pMPO-positive cases were of precursor B-cell lineage and showed increased CD13 or CD15 expression.
- Monoclonal MPO antibody staining was negative in a subset of pMPO-positive cases, indicating potential pMPO antibody non-specificity.
- The Philadelphia chromosome translocation, t(9;22), was detected in 42% of pMPO-positive cases.
- pMPO-positive ALL exhibited less extramedullary disease and a trend toward improved survival.
Conclusions:
- Polyclonal MPO immunoreactivity occurs in a subset of adult ALL, primarily precursor B-cell ALL.
- The specificity of pMPO antibodies in ALL requires careful consideration, potentially leading to misclassification as biphenotypic leukemia.
- A revision of current diagnostic scoring systems is proposed to accurately incorporate pMPO-positive ALL.
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