WBC, or leukocytes, in normal mammalian blood include segmented neutrophils, band neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Abnormal leukocytes include neutrophils less mature than bands (eg, metamyelocytes, myelocytes, progranulocytes), blast cells of any lineage, mast cells, and neoplastic cells of tissue origin. WBC vary in their site of production, their duration of circulation, and the stimuli that affect their release into and migration out of the vascular bed. Differences in leukocyte physiology account for species differences in normal blood concentrations and their responses in disease. (Also see Reference Guides: Hematologic Reference Ranges a)

The leukogram, a component of the CBC, is an organized tabulation of the total WBC concentration, along with the concentrations of specific WBC types present in the sample, also known as the differential. Knowledge of WBC physiology and the influence of disease processes form the basis for interpreting abnormalities of the leukogram into diagnostic information. Leukogram interpretations vary in diagnostic specificity. Most interpretations define a process rather than a specific diagnosis. Interpreted processes generally fall into four groups: l) physiologic responses that alter vascular hemodynamics; 2) inflammatory, infectious, and immunologic responses; 3) marrow responses to injury; and 4) hematopoietic cell neoplasia. (Also see Diagnostic Procedures for the Private Practice Laboratory: White Blood Cells.)

Last full review/revision July 2011 by Glade Weiser, DVM, DACVP