Expression of IL-18 in psoriasis.

Area of Science:

• Immunology
• Dermatology
• Cytokine research

Background:

• Interleukin-18 (IL-18) is a key cytokine in T-helper 1 (Th1) immune responses, inducing Interferon-gamma (IFN-gamma) production.
• Keratinocytes, monocytes, and macrophages are primary sources of IL-18, with keratinocyte-derived IL-18 implicated in skin immunity.
• The role and processing of IL-18 in psoriatic lesions remain incompletely understood.

Purpose of the Study:

• To investigate IL-18 expression in psoriatic lesional skin.
• To determine if IL-18 in psoriatic scales is processed into its mature, active form.
• To explore the bioactivity and regulation of IL-18 in the context of psoriasis.

Main Methods:

• Immunohistochemistry and Reverse Transcription-Polymerase Chain Reaction (RT-PCR) to assess IL-18 expression.
• Western blotting and Enzyme-Linked Immunosorbent Assay (ELISA) to analyze IL-18 forms in scale extracts.
• Assays for IL-18 bioactivity and IFN-gamma inducibility in peripheral blood mononuclear cells (PBMCs).

Main Results:

• IL-18 expression was significantly elevated in psoriatic lesional skin compared to normal skin.
• Psoriatic scale extracts contained mature IL-18, but predominantly the precursor form, pro-IL-18.
• No detectable IL-18 bioactivity or IFN-gamma induction was observed in psoriatic scales using human PBMCs.

Conclusions:

• Keratinocyte-derived IL-18 is involved in the development of Th1 responses within psoriatic lesions.
• The bioactivity of IL-18 in psoriatic skin inflammation appears to be tightly regulated.
• Further research into IL-18 processing and regulation may offer therapeutic insights for psoriasis.