Detection of antiplatelet antibody in serum and on megakaryocytes of dogs with autoimmune thrombocytopenia.

Blood and bone marrow samples from 13 thrombocytopenic dogs were examined to determine whether immunologic thrombocytopenia existed. Antiplatelet antibody was detected in serum of 8 of the dogs by platelet factor 3 test or its modification. Moderate to strong immunofluorescence of megakaryocytes was noticed in bone marrow smears stained with rabbit anticanine globulin conjugated with fluorescin isothiocyanate. Negative results were obtained with serum and bone marrow samples collected from 6 of the dogs during therapy for autoimmune thrombocytopenia. Clinical and laboratory findings varied in individual patients with circulating antiplatelet antibodies. Thrombocytopenia was present in all the dogs, with platelet counts ranging from less than 3,000 to 20,000/mu1 of blood. Signs of bleeding in tissues and body cavities were present in all dogs, but anemia was evidenced in only 3 dogs. Differential leukocyte counts were variable. Morphologic abnormalities such as vacuolation and reduced or absence of granulation of the cytoplasm and nuclear fragmentation were seen in some megakaryocytes.