Background and Objective:Psoriasis is a common chronic inflammatory, recurrent, immune mediated disease of the skin and joints. Various cells which have been suggested to play a key role in the pathogenesis are T cells, antigen presenting cells (APC's), keratinocytes, Langerhans' cells, macrophages, natural killer cells and plasmacytoid DCs (pDCs), through activation of their TLRs. PDCs are important cell population in psoriasis as they are 16% of the total dermal infiltrate in psoriatic skin lesions.Toll-like receptors are pattern recognition receptors for conserved molecular patterns of pathogenic microorganisms. When TLRs are activated by ligands exposure, series of actions take place and end by modulating the expression of many immune response genes.Under certain circumstances, self nucleic acids can trigger TLR 7 and TLR 9, which can lead to autoimmune diseases such as psoriasis.Patients & Methods:The study included 15 psoriatic patients (plaque type) and 15 controls, patients received 36 sessions of phototherapy (NB-UVB). Skin biopsies were taken from all the patients (before & after NB-UVB) and controls and were assessed for TLR 7 & TLR 9 by PCR.Results:Showed significant difference between patients and controls as regards TLR 7 & TLR 9. In addition a significant decrease in thier levels in patients after phototherapy with NB-UVB.Conclusion:TLR 7 and TLR 9 may play a role in the pathogenesis of poriasis. Decrease in their levels after NB-UVB may be one of the therapeutic mechanisms of NB-UVB in psoriasis.