IMMUNE CYTOLYSIS: ELECTRON MICROSCOPIC LOCALIZATION OF CELLULAR ANTIGENS WITH FERRITIN-ANTIBODY CONJUGATES

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Abstract
Immune gamma globulin from the serum of rabbits immunized against whole Krebs ascites tumor cells was coupled to ferritin by the diiso-cyanate method of Singer. The conjugates were incubated in vitro with ascites cells, and the location of the ferritin determined by electron microscopy of the thin-sectioned material. The conjugates were shown to localize specifically on antigens of the cell membrane but did not pass directly through the cell membrane into the cytoplasmic matrix, unless complement was added to the system. In broken cell preparations incubated with the conjugates, antibody was shown to combine with amorphous material and with structures derived from the cell membrane and smooth membranes of the endoplasmic reticulum. The data are consistent with the view that cytotoxic antibodies fix primarily to surface antigens of the cell membrane. The subsequent action of complement establishes the permeability defect that induces osmotic lysis of the cell and permits antibody to pass into the cell where it may act in a similar fashion on intracellular organelles.