Document Type


Subject Area(s)

Animals; Cytokines (genetics, metabolism); Dermatitis (genetics, metabolism, pathology); Disease Models, Animal; Imiquimod (adverse effects, pharmacology); Inflammation (chemically induced, genetics, metabolism, pathology); Membrane Glycoproteins (analysis, genetics, metabolism); Membrane Transport Proteins (genetics, metabolism); Mice; Mice, Transgenic; Psoriasis (chemically induced, genetics, metabolism, pathology); Skin (metabolism, pathology); Toll-Like Receptor 7 (analysis, genetics, metabolism)


There is competing evidence that plasmacytoid dendritic cells (pDC), the most potent source of IFN-I, may initiate psoriasis. We targeted pDC function using the slc15a4 loss-of-function mouse whose pDC are unresponsive to TLR agonists. slc15a4 treated with the topical TLR7-agonist imiquimod (IMQ) demonstrated decreased epidermal thickening 24 hours post-treatment which was more pronounced by day 5 as compared to wildtype mice. These findings were specific to the acute IMQ model and not the protracted IL23 model that drives inflammation downstream of TLR activation. Systemically, slc15a4 was required for IMQ-induced weight loss and cutaneous accumulation of CD4+ and Siglec H+, but not CD11b+ cells. Consistent with this phenotype and the function of slc15a4, induction of IFN-I was virtually absent systemically and via cutaneous gene expression. Induction of other inflammatory cytokines (cytokine storm) was modestly blunted in slc15a4 except for inflammasome-associated genes consistent with slc15a4 being required for TLR7-mediated (but not inflammasome-mediated) inflammation downstream of IMQ. Surprisingly, only IFN-I gene expression was suppressed within IMQ-treated skin. Other genes including conserved psoriasiform trademark gene expression were augmented in slc15a4 versus littermate controls. Taken together, we have identified a role for slc15a4 but not canonical psoriasiform genes in the imiquimod model of psoriasiform dermatitis.

Digital Object Identifier (DOI)


© The Author(s) 2018 This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit

APA Citation

Griffith, A., Zaidi, A., Pietro, A., Hadiono, M., Yang, J., Davis, R., & Popkin, D. (2018). A requirement for slc15a4 in imiquimod-induced systemic inflammation and psoriasiform inflammation in mice. Scientific Reports, 8(1).