Intracellular localization of certain membrane glycoproteins in mouse T‐lymphoma cells using immunoferrtin staining of ultrathin frozen sections

Comparative studies on the cellular morphology of cultured mouse T‐lymphoma cells (with particular emphasis on organelles and membrane‐associated materials) were conducted using both frozen thin sections and epon thin sections. Due to the fact that the frozen thin sectioning technique allows antigenicity to be retained and also permits good accessbility of the external macromolecular reagents to the interior of the cell, we have been able to explore the intracellular localization of some membrane glycoproteins such as Con A‐binding sites and viral membrane glycoprotein, gp 69/71. Our data indicate that most of the membranous cellular structures (e.g., rough endoplamic reticulum, vesicles, Golgi and nuclear envelope) contain the Con A‐specific sugars, mannose, and glucose. In addition, we have found that intracellular gp 69/71 molecules exist in an aggregated form at the terminal region of cisternae of rough endoplasmic reticulum and in vesicles of two size ranges (0.1 to 0.15 μ and 0.3 to 0.4μm) as wells as in the cytoplasm close to the plasma membrane. These findings have not only confirmed close some of the previous biochemical data but have also provided new information concening the biochemical nature of intracellular membrane components and the possible biosynthetic fate of membrane precursor molecules.