Binding of concanavalin-A to critical-point-dried and freeze-dried human lymphocytes

When human lymphocytes are treated with concanavalin-A (con A) and hemocyanin, the hemocyanin marker, which demonstrates con A binding sites, can be visualized by scanning (SEM) and transmission electron microscopy (TEM) on both critical-point-dried and freeze-dried cells. The ability to visualize the hemocyanin marker by SEM, its quantity and distribution, were all similar in lymphocytes prepared by both drying procedures. By TEM, hemocyanin was seen adjacent to the plasma membrane on critical-point-dried lymphocytes. In contrast, freeze-dried cells showed hemocyanin labeling at some distance from the plasma membrane (40-70 nm) as well as adjacent to it. The distribution of hemocyanin corresponded to the thickness of the amorphous coat seen on fixed, freeze-dried cells. Therefore, the extracellular coat on freeze-dried lymphocytes is a carbohydrate-containing glycocalyx.