Three main pieces of evidence suggest the immune system is involved in psoriatic disease. Genes and the immune system go together, working alongside each other all playing a part in the master plan of our bodies.
Your immune system is designed to protect you against disease. It is made up of many white blood cells (T cells) that patrol the body in search of cells and proteins that should not be there. All your cells have special identity tags to help your immune system recognise them. Sometimes, however, the immune system over-reacts or even attacks parts of the body to cause problems.
Evidence suggests that inflammation in the skin and joints is in part directed and maintained by cells of the immune system called T lymphocytes. Under normal circumstances, these cells survey the bloodstream and body tissues for signs of infection and cancer.
If a foreign agent, such as a virus, is found, T lymphocytes destroy the infected cells and send messages into the local area to recruit assistance in clearing the infection. For reasons unknown, T lymphocytes are present in large numbers in the psoriatic skin and inflamed joints of people with psoriatic arthritis.
The activity of these T lymphocytes and the messages that they produce contribute to the thickened epidermis in psoriasis and damage to the joint. Many of the stronger drugs prescribed for psoriatic arthritis such as methotrexate, azathioprine, and steroids serve to reduce the production and/or activity of the cells of the Immune system, including T lymphocytes.
Many of the most potent therapies used to control psoriasis damage the action of immune cells. The drugs attack a wide variety of cells, good and bad.
As more is learned about how immune activity contributes to psoriatic disease, new therapies will be developed that are more specific.
If we can manipulate immune responses more selectively, this could be key to the management of the conditions. Progress is being made and in the future, there is a good chance that psoriatic management will be much simpler.