Lymphocyte-Neutrophilic Granulocyte Aggregates With and Without Associated Spurious Leukopenia in Beagle Dogs

Abstract

Three cases are reported of male Beagle dogs which initially showed indications for clumped cells on the scattergrams of a haematology analyser with automated ‘5-part’ white blood cell, WBC, differentiation using potassium EDTA anticoagulated blood. On analysis of the bloodsmears leucocyte aggregates 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 present but no thrombocytes. In two cases thrombocyte aggregates with leucocytes on the surface (‘inverted’ rosettes) were observed with sodium citrate and lithium heparin anticoagulated blood samples. In one case the leucocyte agglutination seems to be of spontaneous origin because the aggregates were present in the predosing analysis and after placebo treatment. In the other two cases the aggregates arose during the treatment with an experimental medicine. In two cases spurious leukopenia was observed associated with the leucocyte aggregates but in the other case the quantity and distribution over the various classes of white blood cells appeared 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.