The immune effects of Elliptinium (2-methyl-9-hydroxyellipticinium, 9-HME), a chemical recently shown to possess clinical antineoplastic activity, were investigated in mice. Primary antibody responses to T-dependent and T-independent antigens, DTH reactivity and responsiveness to mitogens were significantly depressed only by post treatment with single drug doses of at least 5, mg/kg i.v., i.e. doses clearly above those known to exert full antitumoral effectiveness and to induce lymphoid cell depletion in the same species. Only drug doses in the LD50 range (i.e. 10 mg/kg) reduced the capacity of NK cells and of activated macrophages to express non-specific cytotoxicity towards tumor target cells. When repeated dose regimens were used, significant immune depression was again seen at doses above those displaying chemotherapeutic activity. Data obtained suggest that at chemotherapeutically effective dosages 9-HME possesses in mice a comparatively low immunodepressive potential and that immune cells mediating natural host defence mechanisms appear especially resistant to this drug.
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