What Is Absolute Lymphocytes In Cats?

What Is Absolute Lymphocytes In Cats?

Sometimes a veterinarian needs to order a complete blood count for your cat. Usually referred to as a CBC/WBC count, this is a test that looks at the number of cell fragments (platelets), red blood cells (erythrocytes) and white blood cells (leukocytes) in your cat’s blood; there are various types of these cells and the test looks at all of them. It’s generally performed alongside a blood chemistry panel.

What is “absolute lymphocytes” in cats? Absolute lymphocytes refer to the total number of lymphocytes in your cat’s blood and provide insight into your cat’s immune system.

You’ve arrived on this page because you have questions or concerns about your cat’s blood test results.

  • What does “absolute lymphocytes” mean?
  • What can the vet learn from your cat’s absolute lymphocyte count?
  • What do abnormal results mean? Do you need to worry if the count is unusually low or high?

To find out the answers to these and other questions, read on.

The ups and downs of your cat’s blood count

What is “absolute lymphocytes” in cats? Your cat’s blood count tells the vet a great deal about her health. A blood workup lets the vet know if your cat is anaemic, if your cat is immunocompromised, or if she is suffering from various other conditions. Along with the other types of blood cells, the test counts up all the different white blood cells.

There are five types of white blood cell:

  • basophils
  • eosinophils
  • monocytes
  • neutrophils
  • lymphocytes

These cell categories are further subdivided into different subtypes, including three types of lymphocytes. The “absolute lymphocytes” value on your cat’s blood test results is a measure of the total number of a certain kind of white blood cell known as lymphocytes.

Lymphocytes are found in lymph fluid as well as blood and perform an important role in the immune system. There are three types of lymphocyte:

  • B (bone marrow) cells
  • T (thymus) cells
  • NK (natural killer) cells
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Most of the standard machines used for automated blood analysis by your vet don’t differentiate between these cells, instead simply counting the number of lymphocytes as a whole. The term “absolute lymphocytes” means that the numbers of all these cells are taken together to give the total number of lymphocytes found in the blood sample. As well as the total number of lymphocytes per volume of blood, a test will typically look a the percentage of lymphocytes in the total leukocyte cell count.

It will also check the number of abnormal lymphocytes found in your cat’s blood sample. In a healthy cat, the absolute lymphocyte count will typically be somewhere in the region of 1200 to 1800. The percentage of lymphocytes relative to other white blood cells should be 20 to 45. Because lymphocytes are associated with the immune system, the number and condition of these cells offer valuable information about your cat’s state of health.

An abnormal result tells the vet that your cat may have a health problem and is useful in diagnosing various medical conditions. For example, a value that’s too low could show that your cat is struggling with some condition that’s affecting her immune system and making her more vulnerable to infection. A higher than normal absolute lymphocyte count may indicate that your cat is fighting an infection – or there may be a more serious cause.

Some conditions, such as feline leukaemia, may cause the absolute lymphocyte count to be higher or lower than expected. Later in this article, we’ll look in more detail at what lymphocytes do, what an abnormal lymphocyte count may mean and what to expect if this issue comes up.

Lymphocytes, B cells, T cells, NK cells… I’m confused. What does it all mean?

As previously stated, lymphocytes are a type of white blood cell. They perform important roles in your cat’s immune function. Along with other elements of the immune system, they help her to resist infections and fight off diseases. When an antigen such as a bacteria or virus is detected, B cells go to work attacking the invader with a flood of antibodies — special Y-shaped proteins that are tailored to attack a particular threat.

Meanwhile, the T cells mobilise to fight the infection in two different ways. One set of T cells, known as helper T cells, uses substances called cytokines to direct the immune response. Cytokines are like a messaging system for the other cells in the body, telling them how to respond. Another set of T cells, known as cytotoxic (cell-killing) T cells, generates enzymes that are toxic to infected cells. Once they’ve been activated, the B and T cells leave behind a cellular record of the antigens they’ve encountered so that the immune system can respond more effectively if the same attacker is encountered in the future.

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NK cells are able to tell the difference between normal, healthy cells and unhealthy ones, such as those infected by a virus or mutated to become a tumour cell. Unlike B cells and T cells, NK cells don’t require activation by a previous encounter with an attacker and can immediately recognise many types of abnormal cell. Once an abnormal cell has been detected, it will be attacked using cytotoxic granules and destroyed. Your own immune system uses the very same cells, incidentally — they’re something you have in common with all mammals, including your cat.

My kitty’s absolute lymphocyte value is high. What does that mean?

An abnormally high lymphocyte count indicates that something has stimulated your pet’s immune system and triggered the production of extra lymphocytes. This often happens in the case of an infection and is not necessarily a cause for concern; it can simply be a sign that your cat has recently fought off an illness and is already on the mend. A high lymphocyte count can be a sign that your cat was under some stress when the blood for the sample was drawn.

If your pet really hates going in a carrier, being taken to the vet or is afraid of needles and blood tests, this stress alone can be enough to cause a higher-than-normal lymphocyte count. Lymphocyte levels will drop back to normal once she starts to relax again. Conversely, a happy and excited cat may have a higher-than-expected lymphocyte count. If your kitty is the rare kind who thoroughly enjoys a bit of an outing and appreciates the extra attention that a good vet lavishes on a patient, the excitement this produces can also cause her lymphocytes to rise. Your vet will look at other possible causes, including injuries, infections and immune conditions that could be causing the absolute lymphocyte count to be higher than expected. If your kitty was on some kind of steroid medication for any length of time and has recently stopped, this can make the lymphocyte count spike as your pet’s immune system bounces back from the medicine.

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Another possibility is that your cat is still very young — kittens often have a higher number of lymphocytes than you’d expect in an older cat. Sadly, there are also a number of more serious conditions that can raise the absolute lymphocyte count. These include autoimmune disorders, severe infections, as well as certain cancers and types of leukaemia.

The absolute lymphocyte value on my cat’s blood test was lower than expected. What does this signify?

If your cat is currently on a corticosteroid medication (often given for arthritis or other inflammatory conditions in cats), this can lower her lymphocyte count significantly. Your pet’s lymphocyte count may also go down if her cortisol levels are elevated due to over-production by the adrenal glands, as in Cushing’s Disease. Confusingly enough, while a short period of stress may cause your cat’s lymphocyte count to rise, a prolonged period of stress may cause it to drop below the expected levels. You might see a lower-than-usual count in a recently rescued animal, for example, if her background was a troubled one.

While it’s common for infections to cause the lymphocyte count to rise, there are various infections that could cause your cat’s lymphocytes to drop. One of these is Feline Distemper (Panleukopenia). This is rare nowadays thanks to the development of an effective vaccine; it sometimes appears in kittens before vaccination and in feral or recently rescued animals. Feline Infectious Peritonitis (FIP) is a fatal infection that affects the cat’s abdominal lining and can cause a lowered lymphocyte count, along with fever. Kidney disease is another cause of lowered lymphocytes.

One of the most common reasons for a lowered lymphocyte count in humans is simply old age; while research into the effects of feline ageing on their absolute lymphocyte value is scanty, many vets are of the opinion that lower numbers of lymphocytes in an older pet are likely to be down to her age. Whether your cat’s absolute lymphocyte count is low or high, however, it’s important not to panic. There’s often a simple explanation and while an “abnormal” test may be unnerving it’s usually nothing to worry about.

Article by Barbara Read
Barbara read
Barbara Read is the heart and soul behind CatBeep.com. From her early love for cats to her current trio of feline companions, Barbara's experiences shape her site's tales and tips. While not a vet, her work with shelters offers a unique perspective on cat care and adoption.