Susceptibility of two colonies of Wistar rats to inflammation, with particular reference to delayed hypersensitivity

Two colonies of Wistar rats were tested for their abilities to produce delayed hypersensitivity reactions and other forms of inflammation. Tuck rats, which respond to dextran with an anaphylactoid reaction, produced delayed reactions to tuberculin protein and to ovalbumin in Freund's incomplete adjuvant. On the other hand, NELP rats which do not respond to dextran also produced delayed reactions to tuberculin protein, but only to ovalbumin when this was contained in Freund's complete adjuvant. Rats of both colonies responded to cotton pellet-induced inflammation, but the adult NELP rats showed resistance both to adjuvant-induced and to collagen-induced arthritis, as well as to the production of experimental allergic encephalomyelitis. NELP rats also showed a much greater reticulo-endothelial system phagocytic activity although antibody titres to sheep red blood cells and the mitogenic activity of concanavalin A and of lipopolysaccharide on spleen cells were similar in the two colonies of rats.