Changes in the distribution of laminin α1 chain in psoriatic skin: immunohistochemical study using confocal laser scanning microscopy

Summary Background  Recent studies have demonstrated the presence in psoriatic skin of ultrastructural and molecular alterations in the basement membrane and an altered polarized distribution of the integrins. Previous studies have demonstrated the existence of some epithelial cell lines synthesizing only laminin β and γ chains that, in the absence of the laminin α chain, do not form a distinct basal lamina. Objectives  To investigate a possible reduction/absence of the laminin α1 chain in keratinocytes in psoriatic skin and to correlate this with fibronectin distribution. Methods  Using monoclonal antibodies against the laminin α1 chain or human plasma fibronectin and using confocal laser scanning microscopy, we evaluated the immunohistochemical expression of these two proteins in cutaneous biopsies from involved and uninvolved skin of the sacral region of 12 men with extensive chronic plaque psoriasis. Site‐matched biopsies of normal skin from four men without psoriasis were used as controls. Results  In normal skin antilaminin α1 chain antibodies stained the dermal–epidermal junction in a regular and continuous manner. In involved and uninvolved psoriatic skin large regions of discontinuous immunostaining were observed, mainly at the apex of the dermal papillae; in the same regions, clusters of keratinocytes appeared markedly reactive and fibronectin was overexpressed in the papillary dermis under the interruptions of the basement membrane. Conclusions  The present study defines the location of the laminin α1 chain in involved and uninvolved psoriatic skin and suggests a possible role of the alteration of this chain, together with T‐cell lymphokines and fibronectin, in the dysregulation of cell morphological processes.