CHARACTERIZATION OF BREAST STROMAL FIBROBLASTS - CELL-SURFACE DISTRIBUTION OF COLLAGEN TYPE-IV, LAMININ AND FIBRONECTIN

A number of cells-fibroblasts, chondrocytes and osteoblasts for exampl e-lack the conspicuous cell surface specialisation known as lamina: in stead, they possess subplasmalemmal linear densities (SLDs). These hav e been documented ultrastructurally as having a lamina-like external c omponent but the extent to which they resemble true lamina in terms of protein composition has not been investigated. The relationship of th e external component of the SLD to true lamina was examined in this st udy by light microscope immunostaining, conventional transmission elec tron microscopy and immuno-electronmicroscopy in intralobular stromal fibroblasts. These were studied in normal peri-tumoral breast tissue i n 17 patients undergoing surgery for breast lesions. For ultrastructur al immunostaining the indirect immunoperoxidase procedure was used on cryostat sections followed by embedding in epoxy resin. To varying deg rees, collagen type IV, laminin and fibronectin antibodies stained fib roblasts and macrophages at the light microscope level. Using immuno-e lectronmicroscopy, all three antibodies localised as foci on fibroblas t and macrophage surfaces. These occurred with a frequency comparable to that of SLDs as seen in non-immunostaining ultrathin sections. Thes e observations represent a first attempt to define the protein composi tion of SLDs in fibroblasts in vivo. They provide an opportunity of co mparing these structures with true lamina and form a basis for underst anding how fibroblasts interact with their environment.