The kinetics of mononuclear phagocyte infiltration in neoplasms: Reactions to nonspecific stimuli in a rat fibrosarcoma

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Abstract
The kinetics of macrophage infiltration into a transplantable rat fibrosarcoma were investigated. Monocytes obtained from normal rats and labelled with 51Cr were injected into normal or fibrosarcoma‐bearing rats which had previously been implanted with cotton pellets impregnated with BCG, B. pertussis carrageenan or levan. The subcutaneous tissues of normal and fibrosarcoma‐bearing rats as well as the neoplasm itself were the sites for pellet implantation. The various additives induced an enhancement of macrophage infiltration into cotton pellets implanted for 1 week into subcutaneous tissues of normal rats. No significant effect was found in pellets implanted for 3 or 14 days. Macrophage infiltration into pellets in the neoplasm was consistently reduced when compared with controls. This occurred regardless of the length of time of implantation, the type of substance added to the pellet or (in the case of BCG or B. pertussis) whether the rats were pre‐sensitised to the pellet additive or not. Pellets removed from the subcutaneous tissues of fibrosarcoma‐bearing rats were either similar to or more often higher in radioactivity than those implanted into the neoplasm itself. The results indicate that the capacity of macrophages to respond to inflammatory stimuli is reduced in fibrosarcoma‐bearing rats, but especially in the stroma of the neoplasm.