PD-1 Expression Defines Epidermal CD8+CD103+ T Cells Preferentially Producing IL-17A and Using Skewed TCR Repertoire in Psoriasis

In psoriasis, CD8(+) CD103(+) memory T cells residing in the epidermis represent an effector population capable of maintaining the condition and driving a recurrence of the disease. Tissue-infiltrating CD8(+) T cells expressing PD-1 are regarded as antigen-primed effector cells in others chronic inflammatory diseases. However, the expression and significance of PD-1 on skin-infiltrating CD8(+) T cells in human psoriasis is not known. By analyzing skin-infiltrating T cells from human psoriasis, we found that active psoriatic epidermis contained PD-1 expressing CD8(+) CD103(+) T cells that correlated with the disease severity and histopathology. PD-1(+) CD8(+) CD103(+) T cells possessed a canonical psoriasis-specific resident memory phenotype with IL-23R expression and produced IL-17A, whereas PD-1(-) CD8(+) CD103(+) T cells preferentially produced IFN-gamma. The diversity of skin-infiltrating T cells was dominated by CD4(+) T cells, while CD8(+) T cells, especially CD8(+) CD103(+) T cells, represented an oligoclonal population in active psoriasis. In addition, PD-1(+) CD8(+) CD103(+) T cells used different TCR V beta s from PD-1(-) CD8(+) CD103(+) T cells counterpart. In the early resolved lesion, the composition and functional status of PD-1(+) CD8(+) CD103(+) T cells were markedly altered, while PD-1(-) CD8(+) CD103(+) T cells population was minimally changed. Collectively, PD-1 expression delineates a putative pathogenic subset of epidermal CD8(+) CD103(+) T cells, which possibly play a role in psoriasis pathogenesis.

Automated summary

In human psoriasis, PD-1 expressing CD8(+) CD103(+) T cells in the skin are associated with disease severity and histopathology, indicating a potential pathogenic subset that may play a role in psoriasis pathogenesis.