The stimulatory effects of bearing primary methylcholanthrene‐induced tumors upon the murine lymphoreticular system

These studies explore mechanisms involved in the apparent immunodeficiency associated with the development of primary tumors. Methylcholanthrene fibrosarcomas were induced in five inbred strains of mice, and the cellular parameters of spleen‐cell immunologic function were measured either after the tumors reached a constant size or following a specific period of growth. T‐cell numbers, as indicated by the subpopulation susceptible to anti‐θ and complement cytotoxicity, and T‐cell functions including PHA mitogenicity, primary alloantigen recognition, and T cooperation were decreased proportionately, although they remained unchanged or were increased absolutely. Susceptibility to LPS mitogenicity, an apparent B‐cell function, was increased relatively and absolutely. The B‐cell function of anti‐SRBC production was also increased. Colonyforming units increased in number, but they were insufficient to account for significant proportions of the spleen cell population. It was concluded that the animal bearing a primary MCA tumor is deficient in neither T nor B cells and that the effect of the tumor upon immune function is stimulatory.