Want to get a clear picture of how the immune system in dogs works to protect your pooch? Healthy Dogma is here to make it all clear and simple.

You'll learn what the immune system is, where its different parts are located in your dog, and how it all works to keep them healthy. We'll also talk about its main role and some common health problems that can affect it.

What is the Immune System in Dogs?

The immune system in dogs is a dedicated team of cells, tissues, and organs, all working together. Their main job is to protect your dog's body against parasites, bacteria, and viruses. The dog's immune system has two main parts: the innate immune system and the adaptive immune system.

The innate immune system:

The innate immune system is like the first responders on the scene. It gives quick, general protection. This includes the body's first physical lines of protection, like your dog's skin and the moist linings in their nose and gut (called mucous membranes). The skin keeps many harmful particles from getting in, while those mucous membranes make a thick substance (mucus) that traps anything unwanted before it can go deeper. 

Special cells in this first-line defense, such as neutrophils and macrophages, can also spot and remove these harmful intruders by basically “eating” them, a process known as phagocytosis.

The adaptive immune system:

The adaptive immune system is a more specialized unit, and it has a great memory for past threats. When it recognizes a specific harmful particle it has encountered before, it launches a very targeted attack to neutralize it. This part of the immune system in dogs relies on white blood cells, particularly lymphocytes, and special proteins called antibodies that are made to fight a particular invader. 

Lymphocytes are star players here and come in two main types: B cells and T cells. B cells create antibodies that can latch onto and neutralize specific germs. T cells have a couple of roles: they can directly destroy cells that have been infected, or they can help other immune cells do their roles better.

What Else Does the Immune System in Dogs Do?

The dog’s immune system is constantly on the lookout for and destroying abnormal cells, including those that could turn into cancer. This process, known as immune surveillance, involves finding and eliminating cells that aren't growing correctly. A strong immune system can therefore help lower the risk of tumors developing or getting worse.

The immune system is also a key player when it comes to healing after an injury or surgery. It helps protect the wound from infection by clearing out any harmful particles that try to get in. It also helps tissues repair themselves by releasing special growth factors and sending immune cells to the area. A healthy immune system means faster healing and fewer problems along the way.

Finally, a properly balanced immune system in dogs prevents itself from overreacting and attacking the body's healthy tissues and cells, which is what happens in autoimmune diseases. Good regulation within the immune system helps it tell the difference between “self” and “foreign”, avoiding these harmful internal attacks.

Where is the Dog's Immune System Found?

The immune system in dogs isn't all found in one single spot. Its different parts are actually spread throughout your dog's entire body, and these specific areas are often called lymphoid organs. They're called lymphoid organs because they are the main places where very important white blood cells, known as lymphocytes, grow, develop, and get ready to work. All these lymphocytes play an indispensable role in helping the immune system in dogs do its job correctly. 

You'll find important parts of the dog’s immune system in areas like the blood, the liver, the thymus (a small gland in the chest), the spleen, lymph nodes (often called glands), bone marrow, the lungs, and the intestines. 

If an infection begins in a part of the body that doesn't have many immune system parts, like the skin, the body sends out signals. These signals act like a call for backup, bringing large numbers of immune cells to the infected area to fight off the trouble.

Common Health Issues Affecting the Immune System in Dogs

Problems with the immune system in dogs are generally grouped into three main types: situations where the immune system is too weak (immune deficiencies), conditions where the immune system mistakenly attacks the body (immune-mediated diseases), and cancers that affect the immune system.

Immune deficiencies:

Immune deficiencies mean the immune system in dogs isn't strong enough. A dog can be born with this kind of weakness, or it can develop later in life. When a dog is born with an immune deficiency, it often means their white blood cells don't work right, they can't make enough white blood cells, or they can't produce the necessary antibodies to fight infections. 

Sometimes, the thymus, an important immune organ, doesn't develop properly from birth. Immune deficiencies that appear later can be linked to other widespread health problems, like diabetes (sugar diabetes), the body making too much of a hormone called cortisone (a condition known as hyperadrenocorticism), or cancer.

Immune-mediated diseases:

Immune-mediated diseases happen when the body's immune reaction becomes harmful, or when the immune system in dogs incorrectly targets and attacks the dog's tissues and organs. Examples of these include allergic reactions to food, medications, vaccines, or insect bites. A very severe and life-threatening allergic reaction is called anaphylaxis. 

Another common issue is atopy, which is an allergic skin disease caused by breathing in allergens. Sometimes, the body attacks its own red blood cells, leading to immune-mediated hemolytic anemia. Lupus erythematosus is an inflammatory condition where the body creates “autoantibodies” (antibodies that attack parts of the body itself) that affect the kidneys, joints, skin, and other tissues. 

The pemphigus complex is a group of immune-driven skin and mucous membrane diseases that cause blisters and sores. In immune-mediated thrombocytopenia, the immune system attacks the body's platelets, which are needed for blood clotting. Lastly, immune-mediated polyarthritis causes inflammation in the joints.

Cancer:

Cancer of the immune system in dogs typically involves the body producing too many immune cells. This can also cause an overproduction of immunoglobulins, which are types of antibodies. This kind of cancer can show up as a solid lump (a tumor), as leukemia, where cancerous white blood cells circulate in the blood, or as a tumor in immune system organs like the lymph nodes, thymus, spleen, or bone marrow.

Can I Improve My Dog's Immunity?

Many dog owners wonder if they can help improve their dog's ability to fight off illness. The good news is that there are ways to support the immune system in dogs.

We've prepared a helpful guide focusing on natural ways to improve your dog's immunity, and you can find all the details in our dedicated article on that topic. “Easy Ways to Improve Your Dog’s Immunity”.