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Effect of topical cis‐urocanic acid on local lymph node activation during contact sensitization in mouse, rat and guinea‐pig

Summary Cis‐urocanic acid (cUCA) has been suggested as a mediator of impairment of contact hypersensitivity induction by ultraviolet B (UVB) irradiation. We ascertained whether topical cUCA influences local lymph node activation during induction of contact hypersensitivity. Topical cUCA or vehicle was applied during the local lymph node assay to oxazolone. Local lymph node weight and cell number were assessed in all animals. Additionally, cell proliferation rate was studied in Hartley guinea‐pigs and CHA/Ca mice, whereas activation of antigen‐presenting cells was quantified in NMRI mice and Wistar rats. Topical cUCA suppressed all parameters of local lymph node activation due to oxazolone application in guinea‐pigs. No effect, with the exception of a suppression of antigen‐presenting cell activity, was seen in mice. No effect was seen in rats. The study shows that topical cUCA may suppress local lymph node activation during contact sensitization and suggests that differences between the effect of cUCA in different animal species may exist.