IMMUNO-HISTOLOGIC FEATURES OF NORMAL AND PATHOLOGICAL SCARS - POSSIBLE CLUES TO THE PATHOGENESIS

Keloids and hypertrophic scars are characterized by the presence of a cellular infiltrate much heavier than in normal scars. little is known , however, about the immunophenotypic features of this infiltrate. The aim of this study was to characterize, by Immunohistochemistry, the a ntigenic profile and distribution of immune cells, and to investigate whether differences among keloids hypertrophic and normal scars do exi st. in order to identify possible clues to the pathogenesis of abnorma l scarring. All scars are characterized by the presence of a perivascu lar infiltrate of functionally activated CD4(+) T-lymphocytes (HLA-DR( +), LFA-1(+)) associated with dentritic cells (HLA-DR(+), ICAM-1(+)). This infiltrate, indicative of a delayed-type immune reaction, is heav ier in pathologic scars and shows clear differences compared to normal lesions. The cellular infiltrate is sparse throughout the whole dermi s in normal scars, whereas it is mainly located in the papillary dermi s in hypertrophic scars and keloids. CD36(+) dendritic cells and CD68( +) macrophages are found in large numbers in normal scars, in low numb ers in hypertrophic scars and lower still in keloids, possibly indicat ing defective down-regulatory circuits and scar remodeling processes i n pathologic scars. The results of this study suggest that in situ imm une mechanisms play an important role both in normal wound healing and in the pathogenesis of abnormal scars, and stimulate further investig ations aimed at delineating possible targets for immunomodulating trea tment.