BEHAVIOR OF LAMININ-1 AND TYPE-IV COLLAGEN IN UNINVOLVED PSORIATIC SKIN - IMMUNOHISTOCHEMICAL STUDY USING CONFOCAL LASER-SCANNING MICROSCOPY

Previous studies have demonstrated the presence in psoriatic lesions o f ultrastructural and molecular alterations of the basement membrane a nd an altered polarized distribution of the integrins; this latter alt eration has also been observed in uninvolved skin. The aim of the pres ent study was to determine, by means of immunolocalization with monocl onal antibodies directed against laminin 1 and type IV collagen and us ing confocal scanning laser microscopy, whether there are also alterat ions of the main components of the basement membrane in uninvolved ski n, The findings showed a discontinuous and fragmented staining of lami nin 1 and a normal distribution of type TV collagen, Taking into accou nt both these results and the results of studies on epithelial cell li nes, the authors hypothesize the existence of a functional deficit in psoriatic keratinocytes affecting the synthesis of the al subunit of l aminin, This deficit would explain: (1) the incapacity to produce matu re trimeric laminin; (2) the altered assembly into a distinct basal la mina; (3) the loss of keratinocyte adhesion to the basement membrane; (4) alterations in the polarized distribution of the integrins; and (5 ) the consequent total or partial block of the cell signals regulating the processes of cytomorphosis. Already present in uninvolved skin, a nd enhanced by various irritative stimuli, this situation could be dec isive for the appearance of psoriatic lesions.