What Is the Role of Immune System in Psoriasis?

Immune system is composed of defence cells to protect body against diseases. By functional disruption of those cells, certain diseases occur. In psoriasis, abnormal function of the to immune cells leads to a stimulation and rapid proliferation process in the skin cells. 

Yet, it is not clear that causes of the abnormal function of immune system and the stimulation for skin cells, certain triggering factors are already known to have a role in that process.