We had these study objectives: (1) Verify the leukocyte labeling pattern of the anti-CD80 antibody using flow cytometric analysis on blood from healthy dogs, (2) Determine which cells in bone marrow aspirates from healthy dogs were labeled with the anti-CD80 antibody, and (3) Test our hypothesis by including the anti-CD80 antibody in flow cytometric panels used to immunophenotype canine hematopoietic neoplasms, including leukemia and lymphoma. This evidence concerns the gene CD80 and leukemia.