Differential cell surface distribution of adhesion molecules demonstrated by immuno-scanning electron microscopy

Scanning electron microscopy with immuno-gold labeling revealed that epidermal keratinocytes expressed ICAM-1 and HLA-DR molecules on their surfaces in patterns that differed in mycosis fungoides (MF) and lichenoid reaction (LR). ICAM-1 molecules, visualized as deposits of gold particles, were present as clusters adjacent to the junctions interconnecting the keratinocytes of MF lesions. LFA-1 molecules were seen as granules on the surfaces of all infiltrates, most of which also expressed ICAM-1. HLA-DR molecules were seen continuously along the borders of the individual keratinocytes. In LR, ICAM-1 and HLA-DR were expressed only sparsely on the undersurface of the epidermis, whereas the infiltrates expressed LFA-1 molecules on their surfaces. These findings may explain the differing histological features of MF and LR: ICAM-1 molecules present on the intercellular junctions of MF epidermis lead the LFA-1-bearing cells to migrate into the interspaces of the keratinocytes, thus producing "epidermotropism". These cells aggregate by means of co-expressed ICAM-1 to thus produce the appearance of a "microabscess". In LR, on the other hand, the minimal expression of ICAM-1 on the epidermal undersurface leaves most infiltrates within the dermis, thus producing a "band-like infiltrate" beneath the epidermis.