Identification of acute myeloid leukemia in dogs using flow cytometry with myeloperoxidase, MAC387, and a canine neutrophil-specific antibody.
BACKGROUND
Flow cytometry may be used to determine immunophenotype or lineage of leukemic cells, but few antibodies are available that are specific for cells of monocytic and granulocytic lineage.


OBJECTIVE
The purpose of this study was to evaluate the flow cytometric staining patterns of 3 commercial monoclonal antibodies for monocytes and granulocytes in clinically healthy dogs and in dogs with acute myeloid leukemia (AML).


METHODS
Mouse antihuman macrophage antibody (MAC387), mouse anti-human myeloperoxidase (MPO), and a canine neutrophil-specific antibody (NSA) were evaluated using flow cytometry on blood from 6 clinically healthy control dogs, and on blood (n = 7) and/or bone marrow (n = 2) from 8 dogs with AML. A diagnosis of acute leukemia was confirmed by >30% blasts in bone marrow or >30% blasts in peripheral blood, together with bi- or pancytopenia, circulating CD34-positive blast cells, and clinical signs of disease. Leukemic samples also were evaluated using a wide panel of monoclonal antibodies.


RESULTS
MAC387 stained neutrophils and monocytes from control dogs, although the staining profiles for the 2 cell types differed. MPO and NSA resulted in strong positive staining of neutrophils; MPO also stained monocytes weakly. Lymphocytes did not stain with any of the antibodies. One case was classified as AML of granulocytic lineage (AML-M1), 6 cases were classified as acute monocytic leukemia (AML-M5), and 1 case was classified as acute myelomonocytic leukemia (AML-M4). Neoplastic myeloblasts in the dog with granulocytic AML were positive for MPO, NSA, MAC387, and CD4. All monoblasts from the dogs with AML-M5 were positive for CD14, 5 of 6 were positive for MAC387, and 2 were positive for MPO. NSA staining was negative in the 2 dogs with AML-M5 in which it was evaluated. In the dog with AML-M4 variable percentages of blast cells were positive for CD14, MPO, MAC387, CD4, and NSA.


CONCLUSIONS
Antigens identified by antibodies to MAC387, MPO, and NSA were expressed not just by normal mature neutrophils and monocytes, but also by neoplastic myeloblasts and monoblasts. These 3 antibodies may be useful as part of a wider panel for immunophenotyping AML in dogs.
Villiers
Elizabeth
E
Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, UK. ejv20@cam.ac.uk
Baines
Stephen
S
Law
Anne-Marie
AM
Mallows
Victoria
V
D000818:Animals; D000906:Antibodies / Q000276:immunology*; D000918:Antibody Specificity; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D005434:Flow Cytometry / Q000662:veterinary*; D015470:Leukemia, Myeloid, Acute / Q000175:diagnosis / Q000662:veterinary*; D008264:Macrophages / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology*; D009195:Peroxidase / Q000378:metabolism*
D000906:Antibodies; D009195:Peroxidase