{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,18]],"date-time":"2026-10-18T06:01:13Z","timestamp":1792303273870,"version":"4.4.0"},"reference-count":39,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,11,28]],"date-time":"2025-11-28T00:00:00Z","timestamp":1764288000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Allergic contact dermatitis (ACD) is a cutaneous inflammatory disorder mediated by allergen-specific memory T cells. Methylisothiazolinone (MI), a preservative widely used in industrial and cosmetic products and a component of Kathon CG, has led to a substantial rise in ACD cases. Despite increasing sensitization rates, the innate immune mechanisms and transcriptional responses induced by MI in the skin remain poorly understood.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Individuals with positive patch tests exclusively to MI were recruited at the Contact Dermatitis Clinic of Hospital das Cl\u00ednicas (S\u00e3o Paulo). Participants were re-exposed to MI or saline, and skin biopsies were collected 48 hours later. Healthy MI-negative controls were also exposed to MI and saline. Histopathology and RNA-sequencing were performed. Differentially expressed genes (DEGs) were analyzed, and key findings were validated by qPCR and protein expression of IL-9 and IL-24.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Two distinct MI-responsive groups emerged among ACD patients:ACD-A (high responders): pronounced histopathology (spongiosis, microvesicles). ACD-B (low responders): milder reactions with absence of spongiosis. In ACD-A, MI exposure resulted in 1,588 upregulated and 2,090 downregulated genes compared to ACD-B. DEGs were enriched for innate immune and inflammatory pathways, including IL-24, IL-9, IL-13, and NTRK1 (upregulated), while IL-37 and IL-18 were downregulated. Compared to MI-negative ACD controls, ACD-A showed 1,169 upregulated and 321 downregulated genes. qPCR confirmed increased NTRK1 and IL-9 expression and reduced IL-18 levels. IL-9 and IL-24 protein levels were higher in the dermal layer of ACD-A.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion and Conclusion<\/jats:title>\n                    <jats:p>MI-sensitized individuals exhibit heterogeneous innate immune responses despite uniformly positive patch tests. IL-9, IL-24, and NTRK1 appear to play important roles in the heightened inflammatory response observed in high-responder individuals, while downregulation of IL-18 and IL-37 may contribute to impaired regulatory pathways. These findings highlight previously undescribed heterogeneity in MI-induced ACD and identify potential targets for better understanding disease pathogenesis.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2025.1685396","type":"journal-article","created":{"date-parts":[[2025,11,28]],"date-time":"2025-11-28T06:29:57Z","timestamp":1764311397000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["IL-9 and IL-24 biomarkers in the transcriptional signature of contact dermatitis to methylisothiazolinone"],"prefix":"10.3389","volume":"16","author":[{"given":"Taynah Cohen","family":"de Melo","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mirian Nacagami","family":"Sotto","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Iara 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