The psoriasis-associated antigen, pso p27, is expressed by tryptase-positive cells in psoriatic lesions.

Abstract

Received: 3 May 1994 Key words Psoriasis 9 pso p 27 9 Antigen 9 Mast cells 9 Inflammation A main feature of psoriasis is an inflammatory reaction in the dermis with deposits of immune complexes and infil- tration of inflammatory cells. Recently, we presented evidence that a major antigen in the immune reactions in psoriasis is expressed by a sub- population of dermal cells [1], and that this antigen is probably identical to the psoriasis-associated antigen, pso p27 [2, 3]. Pso p27 is a protein isolated from psoriatic scale, and we have previously described the presence of complement-activating autoantibodies against it [3, 4]. The biological role of this protein has not been identified, but preliminary analyses show that pso p27 has an N-ter- minal amino acid sequence which differs from known se- quenced human proteins (Iversen et al., unpublished ob- servations). In the present study we attempted to characterize the dermal cells expressing the pso p27 antigen. Punch biopsies (6 mm) were obtained under local anaesthesia from lesions of eight patients suffering from static chronic plaque psoriasis. After fixation in ethanol, the biopsy specimens were embedded in paraffin as de- scribed elsewhere, and ultrathin sections (2-3 ~tm) were then prepared [51. Harvima et al. [6] have demonstrated that the presence of tryptase activity in psoriatic lesions is a specific marker for mast cells. To identify mast cells we used an enzyme- histochemical staining method using Z-Gly-Pro-Arg- MNA (Bachem, Bubendorf, Switzerland) as substrate [6, 7]. The thin sections prepared from the skin specimens were incubated with protease inhibitor LBTI (Sigma) for 30 rain [6], followed by incubation with (0.1 mM) Z-Gly- Pro-Arg-MNA and 0.4 mg/ml Fast Black K salt in 0.1 M Tris HC1 for 15 min at room temperature [7] and finally photographed with a Nikon FX-35WA. O.-J, Iversen (5~). H. Lysvand 9 T. Jacobsen - K. Bergh B. A. Lie Department of Microbiology, University Hospital, N-7006 Trondheim, Norway