The most commonly used model for the disease is the Imiquimod-induced skin inflammation model (IMQ-model). In the IMQ model, Aldara cream (containing 5% IMQ) is applied topically to the ear and shaved back skin on mice daily. IMQ is a potent immune activator and a Toll-like receptor (TLR7/8) agonist that elicits erythema, scaling, keratinocyte proliferation and differentiation as well as dermal T cell infiltrations upon administration. The resulting inflammation shows similarities with the human disease and a cytokine pathway mirroring the one seen in the human Ps, with a dependency of Th17 cells and the IL-23 /IL-17 axis.
Onset of skin inflammation is most often observed a few days after initiation of the application of Aldara cream (5% IMQ). The mice develop an acute inflammation in the skin of the ears and back where the cream has been applied, which is enhanced throughout the experiment (termination day 7). Disease development is also accompanied with increased spleen size. Histology of skin resembles human Ps with infiltrating cells and thickening of the epidermis.