Polypodium leucotomos inhibits ultraviolet B radiation-induced immunosuppression

Photodermatol Photoimmunol Photomed. 2008 Jun;24(3):134-41. doi: 10.1111/j.1600-0781.2008.00352.x.


Background: An extract of the tropical fern Polypodium leucotomos (PL) administered orally to mice inhibits ultraviolet B (UVB) radiation-induced skin cancer formation. UVB-induced murine skin cancers occur, in part, because of UVB-induced immunosuppression. Thus, we examined whether PL inhibits UVB-suppression of the induction of contact hypersensitivity (CHS) locally or systemically.

Methods: C57BL/6 mice received standard drinking water or water-containing PL. In the local model, mice were shaved on the dorsum and exposed to 3500 J/m(2) of UVB radiation daily for 4 days. Control mice were not irradiated. After the last irradiation they were sensitized to oxazolone topically at the irradiated site. To examine the ability of PL to inhibit systemic UVB-induced immunosuppression, mice were given 10,000 J/m(2) of UVB radiation once and immunized at a non-exposed site 3 days later. Six days after immunization (in both models), mice were challenged on the ears with oxazolone and 24/48 h ear swelling assessed.

Results: PL in drinking water significantly reduced the inhibition of CHS observed with exposure to UVB radiation in both the local and systemic models.

Conclusions: The ability of PL to inhibit UVB radiation-induced immune suppression may explain, in part, its ability to inhibit UVR-induced skin cancer induction in mice.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Dermatitis, Allergic Contact / etiology
  • Dermatitis, Allergic Contact / immunology*
  • Dermatitis, Allergic Contact / pathology
  • Ear / pathology
  • Immune Tolerance / drug effects*
  • Immune Tolerance / radiation effects
  • Mice
  • Mice, Inbred C57BL
  • Oxazolone / administration & dosage
  • Oxazolone / adverse effects
  • Plant Extracts / pharmacology*
  • Plant Leaves*
  • Polypodium*
  • Radiation Dosage
  • Skin / immunology
  • Skin / pathology
  • Ultraviolet Rays / adverse effects*


  • Plant Extracts
  • Oxazolone