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Several methods of inducing experimental allergic encephalomyelitis (EAE) in rats were examined using different (i) rat strains, (ii) combinations of encephalitogen with different adjuvants, and (iii) sites of encephalitogen inoculation. The time course and severity of the ensuing diseases were determined and methods delineated for inducing a disease with limited variability and high incidence. Omitting the mycobacterial component from the adjuvant eliminated the complication of adjuvant arthritis, which may develop after the appearance of EAE. Encephalitogenic emulsions prepared with an equal volume of frozen guinea pig spinal cord (GPSC) and hexadecane or squalene, injected into two inguinal nodes or one foot pad of Lewis rats, provided two quick and easy ways to induce EAE. Emulsions of encephalitogen with Freund's complete adjuvant or hexadecane, injected into the ear, also induced EAE but lengthened the time between the antigen inoculation and clinical symptoms which accompany the onset of EAE disease. However, injection into the ear offers an advantage over the Newbould technique (direct instillation of encaphalitogen in pre-exposed lymph nodes), since the animals can be confidently predosed with drugs which may reduce lymphoid mass. Effects of local inflammation on systemic drug metabolism are also minimized when using the ear route.

Bacterial cell walls from Str. bovis, Str. lactis, Str. mutans, Str. thermophilus, Str. salivarius, and Str. pyogenes were able to produce polyarthritis in rats but Str. faecalis cell walls were nonarthritogenic. S. aureus cell walls produced extremely severe disease. It was also shown that cell walls from S. epidermidis, B. megaterium, and M. lysodeikticus were nonarthritogenic. A close correlation was observed between development of arthritis and the delayed hypersensitivity to bacterial peptidoglycans but not with the PPD hypersensitivity. It was suggested that the adjuvanticity of bacterial cell walls is needed to induce the disease and that arthritogenicity requires a specific antigen in addition to the presence of an adjuvant-inducing agent.