Changes in cell mediated immune functions by growing tumor

Abstract

Syngeneic strain 2 guinea pigs and hepatoma line 1 were used to study some features of tumor-host relationship. Three hundred thousand tumor cells were given intramuscularly and 5 days later intradermal immunization with living tumor cells was started. At specific time intervals the antitumor response was demonstrated by measuring tumor growth, delayed hypersensitivity reactions at the site of intradermal immunization, in vitro stimulation of peritoneal exudate cells (PEC) with tumor cells and in vitro PEC-mediated cytoxicity. It was found that animals, developing larger tumors than 1 cm in dia had their imumune response abolished. The specificity of the phenomenon was checked by the ability of the spleen of such animals to produce plaque-forming-cells (PFC) against sheep red blood cells (SRBC). The results are discussed in the light of current hypothesis on tumor mediated immuno-depression.