Phenotype identification of CD8αα+T cells infiltrating psoriatic skin lesions

Abstract

Objective To identify the phenotype of CD8αα+T cells locally infiltrating psoriatic skin lesions, and to investigate their role in the occurrence of psoriasis. Methods Skin lesions were obtained from 8 patients with confirmed plaque psoriasis in the progressive stage, who visited the Department of Dermatology in Xijing Hospital affiliated to the Fourth Military Medical University from January to December in 2017. Of the 8 patients, 4 were male and 4 were female, with ages ranging from 24 to 50 years. Normal skin tissues were obtained from discarded skin tissues of 8 healthy controls in plastic surgery. Of the 8 healthy controls, 4 were male and 4 were female, with ages ranged from 23 to 46 years. Immunofluorescence technique was used to investigate the distribution of CD8αα+T cells, determine the proportion of CD8αα+T cell subsets, identify the immunological phenotype of CD8αα+T cells and measure the expression of interleukin-17A (IL-17A) . Results Infiltration of CD8 +T cells was observed in the dermis and epidermis of the 8 psoriatic skin lesions, and the proportion of CD8αα+T cells was 88.48% ± 7.39%. However, only a few CD8+T cells locally infiltrated the control skin tissues, and the proportion of CD8αα+T cells was 14.43% ± 13.14%. There was a significant difference in the proportion of CD8αα+T cells between the psoriatic skin lesions and control skin tissues (t = 11.5, P < 0.01) . CD8αα+T cells in the psoriatic epidermis expressed CD103 (a marker of tissue-resident cells) , while CD8αα+T cells in the psoriatic dermis did not express CD103. CD8αα+T cells in the psoriatic lesions were identified as CD45RA- CCR7- effector T cells, and did not express Foxp3, CD25 and CD122 (markers of CD8+ regulatory T cells) . The proportion of CD8αα+T cells producing IL-17A in the psoriatic lesions was 24.85% ± 4.25%, while CD8αα+T cells in the control skin tissues did not produce IL-17A. There was a significant difference in the proportion of CD8αα+T cells producing IL-17A between the psoriatic skin lesions and control skin tissues (t=5.853, P < 0.01) . Conclusion CD8αα+T cells infiltrating psoriatic lesions are effector memory T cells, and may contribute to the occurrence and development of psoriasis by producing IL-17A. Key words: Psoriasis; CD8-positive T-lymphocytes; Immunophenotyping; Interleukin-17; Fluore- scent antibody technique