MCAM+CD161- Th17 Subset Expressing CD83 Enhances Tc17 Response in Psoriasis

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• Psoriasis pathogenesis involves IL-17-producing CD8+ T cells (Tc17).
• Mechanisms driving Tc17 induction in psoriasis remain largely unknown.
• Identifying pathogenic Th17 subsets is key to understanding Tc17 responses.

Purpose of the Study:

• To elucidate the mechanism by which pathogenic Th17 cells promote Tc17 responses.
• To identify specific cell surface markers and molecular interactions involved in Tc17 induction.
• To investigate the role of these interactions in psoriasis severity.

Main Methods:

• Flow cytometry and gene expression profiling (Serial Analysis of Gene Expression) to characterize Th17 subsets.
• Coculture assays to assess T cell proliferation and cytokine production.
• Analysis of immune cell markers (MCAM, CCR6, CD161, CD83, FOXP3) and cytokine profiles (IL-17A, IL-15).

Main Results:

• A pathogenic Th17 subset, defined as CCR6+MCAM+CD161-CD4+ T cells, abundantly produces IL-17A and is linked to psoriasis severity.
• These CCR6+MCAM+CD161-CD4+ T cells induce CD8+ T cell proliferation and IL-17A production in a CD83-dependent manner.
• CD83 expression on Th17 cells is enhanced by IL-15 and these cells accumulate in psoriatic skin lesions.

Conclusions:

• Pathogenic MCAM+CD161- Th17 cells drive Tc17 responses in psoriasis through IL-17A and CD83-mediated interactions.
• CD83 acts as a critical mediator in the induction of Tc17 cells by pathogenic Th17 cells.
• These findings reveal a novel pathway contributing to psoriasis pathogenesis.