Skin-infiltrating, interleukin-22-producing T cells differentiate pediatric psoriasis from adult psoriasis

Background: Evidence from adult psoriasis studies implicates an imbalance between regulatory and effector T cells, particularly T_H-17-producing T cells, in the pathogenesis of psoriasis. Little is known about the immunopathology of psoriasis in children.

Objective: We sought to functionally characterize the inflammatory cell profiles of psoriatic plaques from pediatric patients and compare them with healthy, age-matched controls and adult psoriasis patients.

Methods: Skin samples from pediatric psoriasis patients and healthy controls were analyzed by multiparameter flow cytometry to determine the dominant immune cell subsets present and cytokines produced.

Results: Lesional tissue from pediatric psoriasis patients had significantly increased interleukin (IL) 22 derived from CD4⁺ and CD8⁺ cells compared with the tissues from healthy pediatric controls and adult psoriasis patients. Tissue from pediatric psoriasis patients had significantly less elevation of IL-17 derived from CD4⁺ and CD8⁺ cells compared with the tissue from adult psoriasis patients. In contrast with the lesions from adult patients, lesional skin in pediatric patients with psoriasis did not have increases in regulatory T cells.

Limitations: This is a pilot study, thus the sample size is small.

Conclusion: Significant differences in IL-17 and IL-22 expression were observed in the pediatric psoriasis patients compared with pediatric healthy controls and adult psoriasis patients. IL-22 might be relevant in the pathogenesis of pediatric psoriasis and represents a potential treatment target unique to pediatric psoriasis.