CD26/dipeptidyl-peptidase IV in psoriatic skin: upregulation and topographical changes

• Published in: British journal of dermatology (1951) Vol. 158; no. 6; pp. 1264 - 1272
• Main Authors: Van Lingen, R.G., Van De Kerkhof, P.C.M., Seyger, M.M.B., De Jong, E.M.G.J., Van Rens, D.W.A., Poll, M.K.P., Zeeuwen, P.L.J.M., Van Erp, P.E.J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2008; Blackwell
• Subjects: Adult; Aged; Biological and medical sciences; Biomarkers - metabolism; CD26; Dermatology; Dipeptidyl Peptidase 4 - immunology; Dipeptidyl Peptidase 4 - metabolism; dipeptidyl-peptidase IV; DPP-IV; Humans; Immunohistochemistry - methods; Medical sciences; Middle Aged; Polymerase Chain Reaction - methods; psoriasis; Psoriasis - enzymology; Psoriasis - immunology; Psoriasis. Parapsoriasis. Lichen; Skin - enzymology; T-Lymphocytes - enzymology; T-Lymphocytes - immunology; Up-Regulation - immunology; Dipeptidyl-peptidase IV; Peptidases; Skin disease; DPP-IV; Psoriasis; Enzyme; Dermatology; Hydrolases; Skin; CD26
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1111/j.1365-2133.2008.08515.x

Summary 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. Objectives  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.