ADHESION MOLECULES ON THE PLASMA-MEMBRANE OF EPIDERMAL-CELLS .2. THE INTERCELLULAR-ADHESION MOLECULE-1 IS CONSTITUTIVELY PRESENT ON THE CELL-SURFACE OF HUMAN RESTING LANGERHANS CELLS

The intercellular adhesion molecule-1 (ICAM-1), which is a member of the immunoglobulin superfamily, is expressed on many cell types, including a variety of cells showing accessory/antigen-presenting capacities and belonging to the monocyte/macrophage or dendritic lineages. Here it is shown that human freshly isolated Langerhans cells (LC) constitutively express ICAM-1, as expected. It seems likely that the amounts of ICAM-1 moieties expressed on the plasma membrane of resting LC are only limited, since they virtually escaped detection by conventional immunofluorescence procedures on epidermal sheets. However, all the observed Birbeck granule-bearing LC showed their clear, although relatively weak, ICAM-1 positivity when more sensitive techniques were employed, such as colloidal goldimmunoelectronmicroscopy using gold particles 15 nm in size and, to an even higher extent, using gold particles 5 nm in size. Because ICAM-1 is a ligand for the adhesive molecule LFA-1, which is expressed on the surface of leukocytes and, especially, lymphocytes, the ICAM-1 (LC)/LFA-1 (T-lymphocytes) interactions might, enabling these cells to adhere together, deliver activation signals to T cells, thus constituting the initial event in the generation of a cutaneous immune response. © 1990.