Lymphocytes
Blood count (CBC) ·Also called: LYM, LYMPH, lymphocyte count
What it is
Lymphocytes include the T and B cells that coordinate targeted immune responses and produce antibodies. They circulate between blood, lymph nodes and tissue, so the blood count is a snapshot of a much larger travelling population.
Why your vet measures it
Lymphopenia — a low count — is the hallmark of the stress leukogram, and seeing it alongside raised neutrophils and low eosinophils is often the single clue that a pet's numbers are reflecting cortisol rather than illness. A high count, particularly a very high one, raises the question of lymphoma or leukaemia.
What a high result can mean
- Chronic antigenic stimulation — long-standing infection or immune stimulation
- Excitement in cats, which briefly pushes lymphocytes up
- Tick-borne infection such as ehrlichiosis in dogs
- Lymphoid leukaemia or lymphoma, usually with a marked and persistent rise
- Hypoadrenocorticism (Addison's disease) in dogs, where the usual stress response is absent
What a low result can mean
- Stress or illness of any kind, through natural cortisol release
- Steroid treatment
- Loss of lymph fluid, as in protein-losing intestinal disease or chylothorax
- Viral infection, including canine distemper and FIV in cats
Dogs and cats differ
Young animals normally run higher lymphocyte counts than adults, so a puppy or kitten at the top of the adult range is usually unremarkable. In cats, a lymphocytosis from adrenaline at the clinic is common and resolves on a calm recheck; in dogs, an unexplained lymphocytosis is taken more seriously.
Questions worth asking your vet
- Does the whole white cell pattern fit a stress response rather than disease?
- If lymphocytes are high, is a recheck or a blood smear review warranted?
- Is my pet on any steroid medication, including ear or skin preparations?
Related terms
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