Suppression of acute and chronic inflammation in tumor-bearing rats.

Both acute and chronic cellular inflammatory reactions were suppressed in rats bearing malignant tumors. Inhibition of the acute inflammatory reactions was demonstrated in immune complex-induced vasculitis and in the accumulation of leukocytes in subcutaneously implanted polyvinyl sponges. Suppression of chronic inflammatory reactions was demonstrated in delayed type hypersensitivity skin reactions. In spite of these suppressed reactions, dermal reactivity to vasopermeability mediators was not diminished. Neither serum complement levels nor numbers of circulating leukocytes were depressed in animals with tumors. Suppression of inflammatory reactions was paralleled by a leukotactic defect which involved both neutrophils and monocytes. This defect could be ascribed to an abnormality in the serum that rendered both cell types leukotactically defective.