IL-17 Expression Negatively Correlates with γδ T-Cell Accumulation in Human Psoriasis Lesions: A Novel Implication for Disease Pathogenesis

Abstract

Psoriasis, an inflammatory autoimmune disease, arises from intricate interactions between the immune system and epithelium. Recent reports have suggested new roles for gamma delta (γδ) T-cells in addition to immune surveillance, however, it remains to be determined whether the mechanisms identified in psoriasis murine models have a similar role in humans. The present study aimed to examine the relationship between IL-17 mRNA level and the γδ T-cell proliferation and to clarify their function in the psoriatic human samples. The study involved 20 patients diagnosed with psoriasis and 16 control subjects. Expression of the IL-17 gene was measured in formalin-fixed paraffin-embedded (FFPE) tissues by qRT-PCR method. TCRγδ⁺ immunofluorescence staining was performed to measure the proliferation and distribution of γδ T-cells in the same samples. In psoriatic lesion biopsies, TCRγδ⁺ T-cell percentage was found higher than the control samples. Additionally, psoriasis patients exhibited elevated levels of IL-17 gene expression. In addition, this study showed a weak negative correlation between γδ T-cell proliferation and IL-17 gene expression in psoriatic skin samples, highlighting the novel effector functions of these cells in psoriasis pathogenesis.