CD56 highCD16 - NK cell involvement in cutaneous lichen planus

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• Lichen planus is an inflammatory skin and mucous membrane disease.
• It involves basal keratinocyte vacuolization and lymphocyte infiltration.
• T lymphocytes are implicated in basal keratinocyte damage via cytotoxic attack.

Purpose of the Study:

• To investigate the characteristics and functional properties of NK lymphocytes in lichen planus.
• To determine the role of NK cells in the pathogenesis of lichen planus.

Main Methods:

• Double staining immunohistochemistry to identify NK cells (CD3-CD56+) in early lichen planus lesions.
• Phenotypic analysis of isolated skin NK cells, including cytotoxicity markers (perforin), natural cytotoxic receptors (NKG2D, NKp44), KIRs, and chemokine receptors (CCR6, CXCR3, CCR5, ChemR23).
• Cytokine release profiling (IFN-γ, TNF-α, IL-22, IL-17, IL-4) from skin NK cells.

Main Results:

• A significant population of NK cells (6.42 ± 2.2%) was found in early lichen planus lesions, primarily at the epidermal-dermal junction.
• Skin NK cells belonged to the CD56highCD16- subset, expressing perforin, NKG2D, NKp44, and specific chemokine receptors for inflamed skin homing.
• These NK cells secreted pro-inflammatory cytokines IFN-γ and TNF-α, with minimal IL-22, IL-17, and IL-4 release.

Conclusions:

• NK cells are present in early lichen planus lesions and exhibit a distinct pro-inflammatory phenotype.
• The identified NK cell subset possesses cytotoxic potential and homing capabilities for inflamed skin.
• These findings suggest a significant pro-inflammatory role for NK lymphocytes in the pathogenesis of lichen planus.