Comparative study of Langerhans cells in normal and pathological human scars. I. Atrophic scars.

In the present study, we investigated Langerhans cells (LCs) in the epidermal component of human atrophic scars, comparing them with those in control skin and normotrophic scars. A preliminary analysis of the histological features was first carried out on vertical serial sections, stained with hematoxylin and eosin. The total epidermal thickness and the thickness of the single epidermal layers were then measured, by means of a digitizing tablet and a morphometric program run on an Apple IIe computer. These parameters were found to be significantly lower (40%) in atrophic scars, if compared to control skin and normotrophic scars (p less than 0.05). CDla-positive and HLA-DR-positive LCs were marked by indirect immunofluorescence. Their position among the epidermal layers, their dimensions, their density and their morphology were examined. In atrophic scars, LCs were densely and evenly distributed in all the epidermal layers. Their density was increased (about 1200 cells/mm2 of epidermal area), if compared to control skin and normotrophic scars (both 300-400 cells/mm2 of epidermal area; p less than 0.001). The CDla-positive definite cell bodies, exhibiting an unstained nucleus, were as large as those evidentiated in the normotrophic scars and twice as much the control skin values (p less than 0.001). The present results provide morphological data that distinguish atrophic scars from control skin and normotrophic scars, and suggest an involvement of the Langerhans cells in this particular case of pathological scarring.