Lymphocyte-neutrophilic granulocyte aggregates with and without associatedspurious leukopenia in Beagle dogs

Three cases are reported of male Beagle dogs which initially showed indicat ions for clumped cells on the scattergrams of a haematology analyser with a utomated '5-part' white blood cell, WBC, differentiation using potassium ED TA anticoagulated blood. On analysis of the bloodsmears leucocyte aggregate s were observed consisting of lymphocytes and neutrophilic granulocytes in ratios varying from 1:1.1 to 1.1.9. The aggregates differed in size from 5 to 10 cells. In aggregates, occasionally eosinophilic granulocytes were pre sent but no thrombocytes. In two cases thrombocyte aggregates with leucocyt es on the surface ('inverted' rosettes) were observed with sodium citrate a nd lithium heparin anticoagulated blood samples. In one case the leucocyte agglutination seems to be of spontaneous origin b ecause the aggregates were present in the predosing analysis and after plac ebo treatment. In the other two cases the aggregates arose during the treat ment with an experimental medicine. In two cases spurious leukopenia was ob served associated with the leucocyte aggregates but in the other case the q uantity and distribution over the various classes of white blood cells appe ared unchanged. Methodology experiments indicated that the formation of the aggregates were temperature- and EDTA-dependent effects on the leucocyte membrane factors, possibly aided by serum globulins.