[Immunohistochemical study for the localization of apolipoprotein AI, B100, and E in normal and psoriatic skin]

Recently many new knowledge about the LDL receptors and LDL-receptor mediated endocytosis of cholesterol have been reported (Goldstein et al. 1979). This phenomenon is also observed in keratinocyte. The use of low density lipoprotein-gold (LDL-gold) technique in electron microscopy demonstrated a reciprocal correlation between cell differentiation and LDL-receptor expression in normal and psoriatic skin which is characterized by keratotic disorder and epidermal hyperproliferation. (Mommaas-Kienhuis et al. 1987). In order to study the interaction between normal skin and lipid, and the affect of lipid to psoriatic skin, we investigated the localization of apolipoprotein AI, B100 and E in epidermis. Six normal skins, ten psoriatic skins and three skins of seborrheic dermatitis were obtained. In normal epidermis, apolipoprotein B100 was markedly detected intercellularly, and apolipoprotein E was observed intracellularly. In contrast, apolipoprotein AI was not detected in epidermis. This result showed that keratinocytes expressed B and E receptors on their surface membrane, connecting with apolipoprotein B100 and apolipoprotein E respectively. But this finding that positive reaction sites were found in all layer of epidermis also suggested that anti-apolipoprotein B100 antibody reacted extracellular cholesterol excreted outside from keratinocytes. In psoriatic skin, the basement membrane of dermo-epidermal junction, the vascular walls and perivascular regions in papillary dermis were stained positively by anti-apolipoprotein AI antibody. But the localization of apolipoprotein B100 and E were similar to normal skin, and they were also detected in the parakeratotic regions in horny layer. These results did not show the relationship between cell differentiation and B, E receptor expression on keratinocyte. And it is suggested that cholesterol metabolism in keratinocyte affected the pathogenesis of psoriasis.