HISTOPATHOLOGICAL CHARACTERIZATION OF MAGNETIC-RESONANCE IMAGING-DETECTABLE BRAIN WHITE-MATTER LESIONS IN A PRIMATE MODEL OF MULTIPLE-SCLEROSIS - A CORRELATIVE STUDY IN THE EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS MODEL IN COMMON MARMOSETS (CALLITHRIX-JACCHUS)

Experimental autoimmune encephalomyelitis in the common marmoset, a no nhuman primate species (Callithrix jacchus), is a new model for multip le sclerosis, Given the close immunological relationship between marmo sets and humans, it is an attractive model for investigating immunopat hological pathways relevant to multiple sclerosis and to evaluate new treatments for the disease. Unlike in the originally documented model, experimental autoimmune encephalomyelitis induced without the use of Bordetella pertussis led to a chronic disease of moderate severity. Th e clinical course of experimental autoimmune encephalomyelitis in the present model was mainly chronic and progressive, but periods of incom plete remission did occur, At the chronic stage of the disease, active ly demyelinating lesions were found together with inactive demyelinate d and remyelinated (shadow) plaques. Before immunization and during cl inically active experimental autoimmune encephalomyelitis, T1- and T2- weighted magnetic resonance brain images were obtained. Correlation of the data from the magnetic resonance images and the neuropathology an alysis revealed that the hyperintense regions in T2-weighted images re presented both active and inactive remyelinating lesions. Quantificati on showed that the number of lesions in T2-weighted magnetic resonance images equalled those found by pathological examination, and thus T2- weighted magnetic resonance imaging can be used to discern the total l esion load. Extravasation of gadolinium-diethylenetriamine-penta-aceti c acid (triple dose) was found only in lesions, which by histopatholog y were shown to be engaged in the process of active demyelination.