Psoriasis is a common chronic, recurring skin disease that is characterised by typical macroscopic and microscopic skin alterations. It is widely accepted that the immune system plays an important role in the pathogenesis of this disorder. Since the early 1990s, the dominant role of a subpopulation of T cells, so-called T1 cells, and their prominent cytokine IFN-γ has been assumed in the pathogenesis of psoriasis. Surprisingly, the comparison of the therapeutic success of treatments with recombinant proteins directed against defined immunological structures shows that those that directly affect T cells (alefacept, efalizumab, Hu-max-CD4, OKTcdr4a) were clearly less effective than those targeting TNF-α (etanercept, adalimumab, infliximab). For this reason, the authors critically re-evaluated the view of psoriasis pathogenesis and postulate that in the majority of patients the T1 cells do not play a dominant role in the clinical, visible stage of this disease.