Plasminogen is present in the basal layer of the epidermis

This study was undertaken to determine whether plasminogen was present within the epidermis. Cryostat secretions of normal human skin were incubated with either whole rabbit antihuman plasminogen serum, the IgG fraction thereof, or the immune-specific IgG fraction thereof, purified by affinity chromatography on plasminogen-Sepharose. Standard indirect immunofluorescent techniques using rhodamine-conjugated goat antirabbit IgG were subsequently employed. Fluorescence was localized to the basal layer of the epidermis. Nonimmune serum and immune serum depleted of its specific antiplasminogen IgG by prior affinity chromatography yielded negative results, demonstrating the specificity of staining for plasminogen. Our findings indicate that plasminogen is present within the epidermis, localized on the peripheral intracytoplasmic area of basal keratinocytes. This finding supports the hypothesis that a proteolytic event mediated by plasminogen activator with the subsequent generation of plasmin may be involved in normal keratinocyte physiology.