Review paper
The role of the subpopulations of dendritic cells in psoriasis

One of the characteristic features of psoriasis is an increase in the amount of dendritic cells (DC) present in the skin and disturbances in their functions. Three pathological subpopulations of DCs can be distinguished in psoriatic skin: lymphoidal DCs, inflammatory dendritic epidermal cells (IDEC) and TNF/iNOS-producing dendritic cells (TIP DC). Lymphoidal DCs are capable of producing significant amounts of IFN-αand can be a major factor causing psoriatic changes. By producing IL-12 and IL-23 IDEC cells stimulate lymphocytes to Th1/Tc1 and Th17 differentiation. TIP DC, by production of TNF-α, induce and sustain inflammation of the skin. Impaired migration of Langerhans cells (LC) is also one of the characteristics of psoriasis. This dysfunction causes LC retention in the skin and leads to activation of effector T and NK/NKT lymphocytes. DC activation is caused by substances produced by microorganisms or heat shock proteins – produced by keratinocytes after heat, chemical and mechanical lesions of the skin. DCs recognize these substances utilizing specific receptors. Deviation of regulatory DC function can play a role in suppressor lymphocyte function aberration, which is observed in psoriasis.