CD1A-AUTOREACTIVE T cells may sense chronic skin barrier compromise through altered sphingomyelin cycle activity, according to new research examining their potential role in atopic dermatitis. The findings suggest a mechanism through which immune cells may detect persistent disruption of the skin barrier, with implications for understanding the pathogenesis of atopic and related disease.
T cells are frequently enriched at barrier tissues, but their role in detecting changes to barrier integrity remains incompletely understood. The researchers focused on CD1a, a Major Histocompatibility Complex class I-like molecule expressed by Langerhans cells. CD1a forms complexes with lipid antigens, enabling recognition by non-classical CD1a-reactive T cells. Although Langerhans cells are altered in lesional skin from patients with atopic dermatitis, the contribution of CD1a to disease pathogenesis has not been extensively investigated.
The researchers combined human skin allergen challenge with single-cell and spatial transcriptomic approaches and functional immunology to investigate the role of CD1a in atopic dermatitis pathogenesis.
Skin allergen challenge in individuals with atopic dermatitis increased concentrations of CCL17 and CCL22, chemokines that promoted migration of CCR4+ T cells. Proteo-transcriptomic analysis at single-cell resolution identified a persistent population of activated skin CD1a+ dendritic cells as a dominant source of these chemokines within lesional skin.
These activated skin dendritic cells had previously been shown to be transiently enriched in human skin wounds. Spatial tissue analyses further showed that they were predominantly located in lesional subepidermal microcompartment clusters, where they co-localised with distinct Th2 cell subpopulations.
Further functional findings indicated that activated skin dendritic cells expressed neutral sphingomyelinase. This enzyme processed inhibitory long-chain sphingomyelin, driving CD1a autoreactivity in Th2 cells.
Together, the data are consistent with a model in which human CD1a-autoreactive T cells detect chronic skin barrier compromise by responding to altered sphingomyelin cycle activity. This mechanism may help explain how persistent barrier disruption is linked to local immune activation in atopic disease.
The study does not establish clinical applications from these findings. However, the results identify CD1a autoreactivity and altered lipid processing as areas for further investigation into the mechanisms underlying atopic and related skin diseases.
Babu RO et al. CD1a-autoreactive T cell sensing of skin barrier compromise. Br J Dermatol. 2026;DOI:10.1093/bjd/ljag391.
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