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Disorders Involving Cell-mediated Immunity (Type IV Reactions) in Dogs


Ian Rodney Tizard

, BVMS, BSc, PhD, DSc (Hons), DACVM, Department of Veterinary Pathobiology, College of Veterinary and Biomedical Sciences, Texas A&M University

Reviewed/Revised Jun 2018 | Modified Oct 2022

This type of reaction occurs when specific types of white blood cells (called T helper cells) respond to antigens and release toxic and inflammatory substances that can damage tissues. Cell-mediated immune reactions can occur in any organ. Treatment usually involves eliminating the offending antigen (if possible) and the use of anti-inflammatory drugs and drugs that suppress the immune system, either alone or in combination.

Granulomatous Reactions

Granulomatous reactions are masses of scar tissue and white blood cells that accumulate around an area of persistent infection. They are triggered by certain types of bacteria or fungi. Although cell-mediated immune responses effectively fight off these infections in most individuals, in a few animals the immune response is only partially effective and results in a mass at the site of infection.

Old Dog Encephalitis

Old dog encephalitis refers to a chronic brain inflammation that can occur in a dog that had distemper Canine Distemper (Hardpad Disease) Canine distemper is a highly contagious, whole body, viral disease of dogs. It is characterized by fever, loss of white blood cells, nasal discharge, digestive signs, and inflammation of the... read more many years earlier. In dogs that have an undetectable infection with the virus, cell-mediated immune reactions may target cells that have been infected by the virus for years.

Contact Hypersensitivity

Contact hypersensitivity results from chemicals reacting with and changing normal skin proteins. These modified skin proteins are perceived as foreign invaders. The body then produces a cell-mediated immune response against them that causes skin damage. This hypersensitivity usually occurs as a result of contact with sensitizing chemicals incorporated into plastic food dishes, plastic collars, and drugs placed on the skin.

Autoimmune Thyroiditis

Autoimmune thyroiditis is an immune-mediated disease that destroys the thyroid gland. The disease is particularly prevalent in Doberman Pinschers, Beagles, Golden Retrievers, and Akitas. Hypothyroidism (decreased production of thyroid hormones) may be the only detectable sign; however, this condition may occur as part of a broader immune disorder, such as lupus ( see Disorders Involving Immune Complexes (Type III Reactions) in Dogs Disorders Involving Immune Complexes (Type III Reactions) in Dogs When antibodies bind to persistent antigens, they can create immune complexes. These antigen-antibody complexes can get lodged in small blood vessels and stimulate inappropriate inflammation... read more ).

Autoimmune Adrenalitis

Autoimmune adrenalitis is caused by infiltration of immune cells into the adrenal glands (located next to each kidney). This causes the destruction of the glands and may lead to Addison disease Addison Disease The adrenal glands are located just in front of the kidneys. The adrenal gland has 2 parts—the cortex and the medulla. The adrenal cortex is subdivided into 3 layers, and each layer produces... read more . Signs of Addison disease include weakness, loss of weight and appetite, diarrhea, and vomiting. Addison disease is most common in young, adult female dogs.

Dry Eye (Keratoconjunctivitis Sicca, Keratitis Sicca)

Dry eye, or keratoconjunctivitis sicca Dry Eye (Keratoconjunctivitis Sicca, or KCS) The lacrimal or tear gland, located at the top outer edge of the eye, produces the watery portion of tears. Nasolacrimal ducts allow tears to drain from each eye into the nose. Disorders of... read more , is caused by an immune reaction that destroys the tear gland. It occurs in dogs, with a genetic predisposition in Cocker Spaniels. Keratoconjunctivitis sicca can also follow a viral infection, trauma, or the use of certain antibiotics. The disease is treated by giving prescription eye drops that contain cyclosporine or other drugs that inhibit the immune response that causes the disorder. Artificial tears and other eye drops may also be indicated. Dogs with dry eye often require life-long treatment.

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