title: CD26/dipeptidyl-peptidase IV in psoriatic skin: upregulation and topographical changes.
abstract: BACKGROUND
  Psoriasis is known to affect 2-3% of the population and can be considered an organ-specific autoimmune disease. CD26/dipeptidyl-peptidase IV (DPP-IV) is a membrane-bound protease with diverse properties. In theory, the expression of CD26/DPP-IV has common grounds with three principal key players of the psoriatic pathogenesis: keratinocytes, T cells and cytokines.
  
  
  OBJECTIVE
  To assess CD26/DPP-IV expression in psoriasis in order to expand on the search for complementary biomarkers related to inflammation and proliferation in psoriasis.
  
  
  METHODS
  The pattern of expression of CD26/DPP-IV was investigated on the mRNA-, protein- and enzyme-functionality level using immunohistochemical, immunofluorescent and enzyme activity labelling techniques.
  
  
  RESULTS
  An 11-fold significant increase of CD26/DPP-IV on the mRNA level was demonstrated in psoriatic epidermal sheets compared with normal skin. Immunohistochemistry on psoriatic sections showed a distinct patchy honeycomb-like CD26/DPP-IV staining in the suprapapillary layers. Moreover, a clearly distinguishable column-like staining pattern throughout the suprabasal compartment along the rete ridges was seen, whereas in normal skin these patterns were absent. Strikingly, CD26/DPP-IV enzyme activity correlated with this immunohistochemical reactivity pattern for the CD26/DPP-IV protein. The T-cell bound expression of CD26/DPP-IV in psoriatic skin was explicitly present, albeit in small quantities.
  
  
  CONCLUSIONS
  Our data provide clear evidence for a versatile upregulation of CD26/DPP-IV expression in psoriatic (epi)dermis. Although the exact functional contribution remains speculative, the topographical distribution of this complex multifunctional protein suggests a suitable role as a complementary biomarker in psoriasis.
authors.affiliation: Department of Dermatology, Radboud University Medical Centre Nijmegen, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands. R.vanlingen@derma.umcn.nl
authors.forename: R G
authors.initials: RG
authors.lastname: van Lingen
authors.forename: P C M
authors.initials: PC
authors.lastname: van de Kerkhof
authors.forename: M M B
authors.initials: MM
authors.lastname: Seyger
authors.forename: E M G J
authors.initials: EM
authors.lastname: de Jong
authors.forename: D W A
authors.initials: DW
authors.lastname: van Rens
authors.forename: M K P
authors.initials: MK
authors.lastname: Poll
authors.forename: P L J M
authors.initials: PL
authors.lastname: Zeeuwen
authors.forename: P E J
authors.initials: PE
authors.lastname: van Erp
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000379:methods; D011565:Psoriasis / Q000201:enzymology* / Q000276:immunology; D012867:Skin / Q000201:enzymology; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology; D015854:Up-Regulation / Q000276:immunology
chemical_list: D015415:Biomarkers; D018819:Dipeptidyl Peptidase 4