Why is it thought that the immune system plays a part in causing psoriasis?

There are several reasons why the immune system is felt to be important in causing psoriasis. Some immuno-suppressive drugs (which damp down some parts of the body s immune reaction) work well in treating psoriasis. It is also a life-long disease, and this is taken as a sign that there is some memory in the immune system that produces the typical rash of psoriasis in response to certain triggers. This memory is part of the way our immune system works in recognising foreign bacteria and fighting them, and explains why immunisation prevents us developing certain diseases.

The way the disease can also clear up without treatment and then flare up again is also typical of a long-term immune response. Finally, some of the genes identified are known to be linked to the way our immune system works.