The White Blood Cell Assay (WBC) is useful in quantifying the number of certain leukocytes
(WBC’s) in a semen sample. The test can distinguish these WBC’s from the general population of
Round Cells (RC) typically reported out in a semen analysis assay. Most human ejaculates contain
some leukocytes, with the predominant cell type being the neutrophil. A high concentration of
WBC’s (leucocytospermia) may indicate the presence of an infection in the reproductive tract.
Furthermore, high concentrations of these cells can have detrimental effects on the semen, including reduction in volume, sperm density,
motility, and forward progression. WBC’s can also impair sperm function as a result of the various
reactive oxygen species they may release, along with possible secretions of cytotoxic cytokines.
The impact of WBC’s can depend on the site at which they enter the semen, the type involved, and
their state of activation. The granules in neutrophilic polymorphic WBC’s contain
peroxidase, which together with hydrogen peroxide form free water and oxygen ions. The oxygen ions oxidize
benzidine which then colors brown, thus staining the cells brown. The WBC stain also contains a
red contrast reagent to differentiate peroxidase positive round cells from peroxidase negative
round cells. Since the WBC concentration is based on the sperm density, a Complete Semen Analysis
assay should be ordered along with this assay.