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 TH -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.