Cutaneous barrier leakage and gut inflammation drive skin disease in Omenn Syndrome.

BACKGROUND: Severe early-onset erythroderma and gut inflammation, with massive tissue infiltration of oligoclonal activated T cells are the hallmark of Omenn Syndrome (OS).

OBJECTIVE: The impact of altered gut homeostasis in the cutaneous manifestations of OS remains to be clarified.

METHODS: We analyzed a cohort of 15 patients with OS and the Rag2R229Q mouse model. Homing phenotype of circulating lymphocytes were analyzed by flow cytometry. Inflammatory cytokines and chemokines were examined in the sera by ELISA and in skin biopsies by immunohistochemistry and in situ RNA hybridization. Experimental colitis was induced in mice by dextran sulfate sodium salt (DSS).

RESULTS: We show that memory/activated T cells from OS patients and from the Rag2R229Q mouse model of OS abundantly express the skin homing receptors Cutaneous Lymphocyte Associated Antigen (CLA) and CCR4, associated with high levels of CCL17 and CCL22 chemokines. Serum levels of LPS are also elevated. A broad Th1/Th2/Th17 inflammatory signature is detected in the periphery and in the skin. Increased Tlr4 expression in the skin of Rag2R229Q mice is associated with enhanced cutaneous inflammation upon local and systemic administration of LPS. Likewise, boosting colitis in Rag2R229Q mice results in increased frequency of CCR4+ splenic T cells and worsening of skin inflammation, as indicated by epidermal thickening, enhanced epithelial cell activation and dermal infiltration by Th1 effector T cells.

CONCLUSIONS: These results support the existence of an interplay between gut and skin that can sustain skin inflammation in OS.