Involvement of macrophages in the pathology of toxic epidermal necrolysis

In toxic epidermal necrolysis (TEN), as in the 'epidermal type' of erythema multiforme, the necrotic epidermis is infiltrated with mononuclear cells. We studied the epidermal infiltrate in seven cases of TEN. About half the cells obtained from pieces of cleaved epidermis dissociated by trypsin were non-epithelial. On cytologic analysis, 80% of these foreign cells exhibited markers of macrophages, 15% were granulocytes and only 5% were lymphocytes (almost exclusively OKT8 T lymphocytes). Semi-thin sections of early prenecrotic lesions showed exocytosis of mononuclear cells within the epidermis with features of satellite cell necrosis and formation of colloid bodies. Almost all these mononuclear cells were macrophages as evidenced by endogenous peroxidase-positive granules. These findings suggest that some kind of macrophage-mediated cytotoxicity may play a role in the necrosis of epidermal cells during TEN.