Guinea pigs prepared with various bacteria and their components to induce a necrotic reaction provoked with muramyldipeptide

Abstract Guinea pigs were given a preparatory injection of heat-killed Mycobacterium tuberculosis in a water-in-mineral oil emulsion. A provocative injection of muramyldipeptide given 3–8 weeks later into the footpads, caused severe inflammation, with hemorrhage and necrosis. In this study, we determined the features of the preparatory injection required to prepare the necrotic reaction. Most mycobacteria-related and Gram-negative bacteria were capable of preparing guinea pigs for the necrotic reaction upon provoactive injection with muramyldipeptide, whereas Gram-positive bacteria did not. Boivin- and Morrison-type lipopolysaccharides, which have a high content of bacterial protein, induced the susceptibility, whereas Westphal-type lipopolysaccharide, which has a low level of the protein, did not. Moreover, the latter adjuvant-active lipopolysaccharide and muramyldipeptide together with ovalbumin also exerted the activity. The development of delayed-type hypersensitivity to the protein antigen seemed to be important for inducing the necrotic reaction. Mice, rats, rabbits and monkeys were injected in the same way as the guinea pigs. The necrotic reaction occurred in the flanks of the monkeys, but not in the other animals. A similar necrotic reaction also occurred in the flanks of guinea pigs given live BCG cells in phosphate-buffed saline as well as the heat-killed M. tuberculosis in water-in-mineral oil emulsion upon provoactive injection with muramyldipeptide. These findings suggested that the induction is associated with the development of delayed-type hypersensitivity to the protein antigen administered in the preparatory injection.