Improvements for Consistently Inducing Experimental Allergic Encephalomyelitis (EAE) in Rats: I. Without Using Mycobacterium. II. Inoculating Encephalitogen into the Ear

Abstract

Summary

Several methods of inducing experimental allergic encephalomyelitis (EAE) in rats were examined using different (i) rat strains, (ii) combinations of ence-phalitogen 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. En-cephalitogenic 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 encephalitogen 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.

The studies were supported by the U.S. Public Health Service through Grant No. 15759. We are much indebted to Drs. Osamu Kohashi and Brian Newbould for helpful discussions, to Jack Fitzgerald and Rosemary Stremel for assistance in handling the animals, and to Mrs. Sheryl Lumas for preparing the manuscript.