White Blood Cells On Dog SkinUpdated 8 months ago

White blood cells (WBC) are immune cells that react to the presence of inflammation (redness) or infection by microbes (bacteria and/or yeast). 

Produced in the bone marrow, they squeeze out of blood vessels to “crawl” toward crisis areas of the body. The two types of WBC most often seen under the microscope (1000x magnification) in a skin swab sample cytology are neutrophils and lymphocytes. Neutrophils are the most common immune cell and first line of defense against microbes, sometimes seen stuffed with the bacteria they’ve gobbled up. Based on their appearance, they get categorized as either degenerate or non-degenerate. A neutrophil that is non-degenerate is “ready for battle” while the degenerate neutrophil is “in battle”. 

Similarly, a non-reactive lymphocyte is the “ready for battle” version while the reactive lymphocyte is the “in battle” version. Lymphocytes are second-line defenders, using the more targeted antibody-antigen weaponry to kill invading microbes. Mast cells are yet another type of white blood cell that can be found on a skin swab sample cytology. However, their presence on the skin surface is more concerning. These cellular “beanbags” are stuffed full of histamine packets (granules). Histamine is important in immune defense to help other white blood cells get to the site of injury or infection (e.g., the swelling from a mosquito bite). “Ready for battle” mast cells are granulated (full of granules) while “in battle” mast cells are degranulated, meaning they are releasing their histamine granules into the surrounding area. When mast cells are found on skin swab cytology (granulated or degranulated), this skin area should get examined by a veterinarian since these immune cells are also a common form of skin cancer (especially in certain breeds like boxers, some terriers, and Labrador retrievers). Mast cell tumors of the skin are often treatable/curable if caught early enough. 

While all these microscopic distinctions can seem nuanced, such classifications help veterinarians distinguish inflammation versus infection, acute versus chronic skin conditions, and even help screen for cancer. This in turn helps them choose the best treatment for your pet. If the white blood cell count is high (1+, 2+, 3+, 4+) in your dog’s skin swab samples (if even occasional mast cells), and/or with one or more clinical signs (e.g., scratching or chewing at the swabbed area), then a veterinary physical exam of your dog’s skin is needed.

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