Spong aggregation factor (AF), the large glycoprotein complex involved in species specific aggregation is the first aggregation factor to be visualized on the surface of aggregating cells. It apparently functions by a single macromolecule bridging between two cells with some arms extending to one cell and some to another. Many such linkages ligate adhering cells. It is a model of specificity of cellular interactions.
NIH ExPorter
NIH ExPorter