title: Expression of interleukin-12 is increased in psoriatic skin.
abstract: 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.
authors.affiliation: Dermatological Clinic and Institute of Immunology and Allergology, University of Bern, Inselspital, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Yawalkar
authors.forename: S
authors.initials: S
authors.lastname: Karlen
authors.forename: R
authors.initials: R
authors.lastname: Hunger
authors.forename: C U
authors.initials: CU
authors.lastname: Brand
authors.forename: L R
authors.initials: LR
authors.lastname: Braathen
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D003593:Cytoplasm / Q000737:chemistry; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D018664:Interleukin-12 / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D008875:Middle Aged; D011565:Psoriasis / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000737:chemistry* / Q000473:pathology
chemical_list: D012333:RNA, Messenger; D018664:Interleukin-12