IN-VIVO MRI AND ITS HISTOLOGICAL CORRELATES IN ACUTE ADOPTIVE TRANSFER EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS - QUANTIFICATION OF INFLAMMATION AND EDEMA

In vivo proton MRI was carried out on a 7 Tesla System at 2-3 day inte rvals over 10 days in rats with adoptive transfer experimental allergi c encephalomyelitis (AT-EAE), an animal model of some aspects of multi ple sclerosis. In order to assess the integrity of the blood-brain bar rier (BBB), MRI was performed by acquiring quantitative MR-relaxation time T-1 images of the AT-EAE rat brain before and after i.v. injectio n of gadolinium-diethylene triaminepentaacetic acid (Gd-DTPA) using an ultrafast MRI technique. The MRI findings were compared with the immu nohistochemical stain of T cells, macrophages and albumin and, in addi tion, apoptosis of T cells was assessed using in situ nick translation (ISNT). Prior to injection of Gd-DTPA, an increase of T-1 times in th e brain of the AT-EAE rats was observed, which paralleled the time cou rse of albumin in histological sections. These were MRI findings obser ved well before the onset of major cellular infiltration and before th e onset of clinical signs. After i.v. injection of Gd-DTPA the observe d decrease of T-1 times paralleled macrophage activation, and less clo sely T-cell infiltration. Our results provide evidence that using MRI, it is possible to assess quantitatively the breach of the BBB and to distinguish in vivo between two components of the early phase of the l esion, inflammatory infiltrates and vasogenic oedema.