Dogs

The function of the immune system is to recognize and destroy invading microbes and renegade body cells that have become cancerous. If the immune system is oversensitive or fails to switch off properly, this results in allergies or autoimmune diseases; these conditions are being diagnosed with increasing frequency in dogs. Dogs bred for purpose rather than conformity(working shepeherds, sled dogs etc) tend to have less problems with sensistive immune systems, and infirmity is bred out.

Antibodies and immunity
Antibodies are proteins manufactured by specialized white blood cells. They act like markers or tags, identifying bacterial proteins (antigens), chemicals, and cells to be dealt with by other parts of the immune system. Mothers pass antibodies to their young in the first milk the pups consume (colostrum) as temporary protection . These maternal antibodies drop to low levels by the time a pup is 10-12 weeks old.

Managing the immune system
lets manipulate the immune system in wo different ways. By administering vaccines to a dog, they can stimulate he immune system to produce new antibodies, protecting the dog against a specific germ. Vets can also suppress a dog's immune system when it becomes overactive, such as in autoimmune conditions or allergic reactions.

Autoimmune disorders
Autoimmune or "immune-mediated" problems occur when a dog's immune system malfunctions, losing the ability to differentiate between dangerous particles, such as invading bacteria, and the normal cells in a dog's body; the immune system then targets and destroys these cells or tissues. For example, underactive thyroid problems in dogs can be caused by the immune system attacking the thyroid glands. Autoimmune haemolytic anaemia (AIHA), a rare blood disease, is caused when the immune system destroys red blood cells.

Immune complex diseases
Antibodies sometimes combine with antigens producing "antibody - antigen complexes". These are also known as "immune complexes", and are normally filtered out of the general blood circulation. However, they are sometimes deposited and build up in joint capsules, in kidneys, or in the walls of blood vessels, where they attract the attention of other parts of the immune system, leading to local inflammation and tissue damage. The most common form of immune complex disease is immune-mediated arthritis in joints.

Diagnosing and Treating allergy
Vets identify allergies by examining breeding history, using skin and blood tests, implementing altered or novel diets, or by temporarily removing a dog from its normal environment. Yet finding specific causes for allergies is frustratingly difficult. For immediate relief from the symptoms, vets will prescribe drugs such as antihistamines, and may recommend essential fatty acid (EFA) supplements.