When a foreign substance, also known as an antigen, is present, it activates a specific type of white blood cell called a T-cell. These cells, considered by many to be the “generals” of the immune system, are in charge of coordinating the immune response which will neutralize a foreign substance.
One part of this response includes the release of interleukins, which are types of cytokines or nonantibody proteins that the immune system uses to communicate messages. One of these cytokines is TNF-alpha.
A healthy immune system can clear itself of TNF-alpha, but in psoriatic arthritis, something happens to activate the T-cells to work overtime. As a result, they begin acting as if they are fighting off an infection, which in turn, signals the production of an excess amount of TNF-alpha. As TNF-alpha builds up, the messages it communicates create a cascade of events, which send more and more T-cells to the affected area.
In psoriasis, the result is the rapid growth of skin cells. Skin cells can grow up to 10 times faster than normal in people with psoriasis. When this occurs, the cells pile up at the skin's surface and lesions form. In psoriatic arthritis, the overproduction of TNF-alpha and the mixed messages it communicates results in joint inflammation, which usually produces joint pain and stiffness, tissue damage and other symptoms associated with psoriatic arthritis.