Immunotherapy models in experimental animals

Tumor-host cell interactions in rats bearing Shay chloroma--ultrastructural observations in animals receiving specific and nonspecific cancer immunotherapy

Tumors of the rats bearing Shay chloroma treated with specific (polymerised tumor particles) and nonspecific (PPD tuberculin) cancer immunotherapy were assessed on electron microscopy with special emphasis on the interactions between the host's effector cells and the tumor targets. Attempt was made to cast light on the differences previously found in the effects of these two immunotherapy models on this particular tumor. Lymphocytes were found apposited to the tumor cells in all animals, but the nature of this contact varied from intimate in series B and C (animals receiving PPD) to extremely loose in series A (specific mode of therapy instituted). The same was true with the cells of the MPS (mononuclear phagocyte system), which sometimes seemed to wrap the tumor cells by their slender cytoplasmic processes. A prominent hypertrophy and orientation of the Golgi complex of a small lymphocyte, recently shown to be characteristic of cytolytic T-cells in vitro, was visualized in one case of series C. The observations were interpreted to lend support to the idea that blocking activity due to the polymerised strong tumor antigens could be responsible for the adverse effects of the active specific cancer immunotherapy in this particular system.