EXPRESSION OF ENDOGLIN IN THE TRANSITION BETWEEN PSORIATIC UNINVOLVEDAND INVOLVED SKIN

Endoglin is a glycoprotein which is predominantly expressed on endothe lial cells. It is upregulated under inflammatory conditions as well as in skin lesions where endothelial cell proliferation occurs. Endoglin has the capacity to bind transforming growth factor beta (TGF-beta) a nd can reduce the bioavailability of TGF-beta. TGF-beta has a growth-i nhibiting effect on keratinocytes and a restraining influence on the e xtravasation of peripheral white blood cells. In order to find out how endoglin is expressed in the margin zone of psoriatic plaques and how it correlates with the appearance of an inflammatory infiltrate, punc h biopsies were taken from the margin zone of actively spreading psori atic plaques in 8 patients. Indirect immunoperoxidase staining was per formed using PAL-E (vascular endothelium), PN-E2 (anti-endoglin) and T 11 (T-lymphocytes). In all patients it was found that the appearance o f parakeratosis correlated with a clear increase of PN-E2 expression. PAL-E and PN-E2 expression was assessed, using a 5-point scale. Thus a tendency to decreased PN-E2 expression in uninvolved skin compared to PAL-E expression was found within the margin zone (1.6+/-0.4 and 2.2/-0.4, respectively), whereas in involved skin PN-E2 expression and PA L-E expression mere in agreement (2.6+/-0.5 and 2.6+/-0.5 respectively ), suggesting that in the overt plaque all endothelium is in a so-call ed activated state. Also correlating with PN-E2 expression was the app earance of a huge dermal lymphocytic infiltrate and epidermal T-lympho cytic expression. The present study lends further support for a permis sive role of endoglin expression in the development of the psoriatic l esion.