Expression of interleukin-12 is increased in psoriatic skin

J Invest Dermatol. 1998 Dec;111(6):1053-7. doi: 10.1046/j.1523-1747.1998.00446.x.


Although the precise underlying pathomechanisms of psoriasis have not been fully elucidated, previous reports suggest that T helper 1-type cytokines are critically involved in the pathogenesis of this disease. Interleukin-12 (IL-12), a heterodimeric cytokine, has been suggested to play a major role in the development of T helper 1 cell responses. In this study, the presence of IL-12 mRNA and protein was investigated in normal human skin as well as nonlesional and lesional psoriatic skin. Messenger RNA levels were determined in biopsy specimens by a standard and a nested reverse transcriptase-polymerase chain reaction method. Additionally, IL-12 protein expression was analyzed in situ by immunohistochemistry using an antibody recognizing IL-12 p70. Whereas specific transcripts for IL-12 p35 were reproducibly detected without any significant differences in all samples, enhanced IL-12 p40 mRNA signals were only found in lesional psoriatic skin as compared with normal and nonlesional psoriatic skin. Furthermore, immunoreactivity for IL-12 p70 was markedly increased in the psoriatic skin lesions and was predominantly expressed on mononuclear cells in the dermis. In conclusion, our data suggest a critical role for IL-12 in promoting and maintaining T cell activation and inducing T helper 1-type cytokines such as interferon-gamma in psoriasis. We speculate that IL-12 might be a key cytokine in the pathogenesis of psoriasis.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Biopsy
  • Cytoplasm / chemistry
  • Female
  • Gene Expression
  • Humans
  • Immunohistochemistry
  • Interleukin-12 / biosynthesis*
  • Interleukin-12 / genetics
  • Male
  • Middle Aged
  • Psoriasis / metabolism*
  • Psoriasis / pathology
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Skin / chemistry*
  • Skin / pathology


  • RNA, Messenger
  • Interleukin-12