Skin-Resident Memory T Cells: Pathogenesis and Implication for the Treatment of Psoriasis

Tissue-resident memory T cells (T(RM)) stay in the peripheral tissues for long periods of time, do not recirculate, and provide the first line of adaptive immune response in the residing tissues. Although T(RM) originate from circulating T cells, T(RM) are physiologically distinct from circulating T cells with the expression of tissue-residency markers, such as CD69 and CD103, and the characteristic profile of transcription factors. Besides defense against pathogens, the functional skew of skin T(RM) is indicated in chronic skin inflammatory diseases. In psoriasis, IL-17A-producing CD8(+) T(RM) are regarded as one of the pathogenic populations in skin. Although no licensed drugs that directly and specifically inhibit the activity of skin T(RM) are available to date, psoriatic skin T(RM) are affected in the current treatments of psoriasis. Targeting skin T(RM) or using T(RM) as a potential index for disease severity can be an attractive strategy in psoriasis.