THE CYTOTOXIC ACTION OF IMMUNE GAMMA GLOBULIN AND COMPLEMENT ON KREBS ASCITES TUMOR CELLS

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Abstract
Krebs ascites tumor cells were studied by phase and electron microscopy after in vitro treatment with rabbit anti-tumor gamma globulin and complement. Cells treated with immune globulin alone displayed agglutination under phase and a distinctive cell membrane alteration when sections were studied by electron microscopy. The cell membrane alteration appeared as a focal, labyrinthine projection and invagination of the cell surface. The change appeared structurally similar to pinocytosis as described in other cell types. The alteration appeared to favor agglutination, as the projections of apposed cells frequently interdigitated. Addition of complement to the above system caused an initial focal outpouching of the cytoplasm, followed by uniform cytoplasmic swelling with a marked lowering of the cytoplasmic refractive index. Cell lysis did not occur under the conditions of incubation. Electron microscopy revealed folded but intact cell membranes, expansion of the cytoplasmic space, and peripheral loss of the free osmiophilic granules of the cytoplasm. Mitochondria and endo-plasmic reticulum were severely swollen. Nuclei were intact except for widening of the nuclear pores. The distinctive cell membrane change suggests that the cell surface is an important site of antigen-antibody complexing The damage to intracytoplasmic organelles after the addition of complement provides a functional basis for the cytotoxic action of antibody and complement.