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Urocanic acid suppresses induction of immunity in human skin
Author(s) -
Dahl Mark V.,
McEwen Gerald N.,
Katz H. Irving
Publication year - 2010
Publication title -
photodermatology, photoimmunology and photomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.736
H-Index - 60
eISSN - 1600-0781
pISSN - 0905-4383
DOI - 10.1111/j.1600-0781.2010.00550.x
Subject(s) - urocanic acid , sensitization , erythema , immunity , human skin , in vivo , medicine , immune system , immunology , cellular immunity , in vitro , chemistry , biology , biochemistry , enzyme , microbiology and biotechnology , genetics , histidine
Background/Purpose:Trans ‐urocanic acid is isomerized to cis ‐urocanic acid (C‐UCA) by ultraviolet radiation. C‐UCA suppresses immunity in vitro and in vivo in animals; its effect on human skin is unknown. We sought to determine whether its topical application to normal skin suppresses induction of immunity to dinitrochlorobenzene (DNCB). Methods: Forty subjects applied C‐UCA (0%, 0.02%, 0.2%, or 2%) for 17 days. A 40‐mcg dose of DNCB was then applied to induce immunity. Subjects were challenged for immunity at 6‐week follow‐up by occluding doses of DNCB (0, 3.125, 6.25, or 12.5 mcg) on untreated normal skin. Induced immunity was measured by area of erythema and induration 2 and 4 days postchallenge. Results: No significant differences were found in incidence of sensitization by C‐UCA concentration ( P =.59). DNCB sensitization developed in all 10 subjects induced through 0% C‐UCA (placebo); only 23 of 30 patients were sensitized through skin treated with C‐UCA. Mean areas of erythema and induration induced through C‐UCA‐treated skin were less than those in controls ( P <0.05). The number of Langerhans cells in C‐UCA‐treated skin was unaffected. Laboratory tests of immune function and lymphocyte numbers were unchanged. Conclusion: Topically applied C‐UCA blunts normal induction responses to a cutaneous sensitizer.