An Overactive Immune System

The helper T-cells activate and deactivate parts of the immune system, but sometimes they the misinterpret the instructions.

They may activate the immune system when the cat's body is not being threatened by dangerous microbes or cancer cells, but when it is simply in cont with normally innocuous substances, such as foods, flea saliva, house dust, or plant pollens.

These substances can trigger an allergic reaction, which may appear as anything from itchy skin, watery eyes, sneezing, or asthma to vomiting or diarrhea.

Problems can also arise with immune responses if the suppressor T-cells do not carry out their "turning off duties effectively.

In this case, the immune system remains in overdrive, and it may erroneously start attacking a specific part of the cat's own body - for example, the red blood cells. When this self-destructive reaction occurs, it is called autoimmune disease.

Renal amyloidosis, a type of kidney failure seen in cats, is one specific example of an autoimmune disease. Veterinarians are increasingly diagnosing both allergies and autoimmune diseases in cats.

While this may be due in part to improved diagnostic methods, many veterinarians feel that both of these problems are increasing in frequency among cats. The corticosteroid group of drugs are used to suppress an over active immune system.