Partial inhibition of AT-EAE by an antibody to ICAM-1: clinico-histological and MRI studies.

The role of quantitative proton magnetic resonance imaging (MRI) for the evaluation of immunopathological lesions in the CNS was studied in adoptively transferred experimental allergic encephalomyelitis (AT-EAE). We utilized a recently established treatment model, inhibition of the cell adhesion molecule ICAM-1 by the monoclonal antibody 1A-29. The animals were scanned on days 3, 5 and 7 after injection of encephalitogenic T-cells, before and after bolus injection of Gd-DTPA by performing T1-measurements to assess the integrity of the blood-brain barrier (BBB). On day 7, immunohistochemistry was performed looking for T-cells, activated macrophages, and albumin staining. There was clinical evidence of partial inhibition of AT-EAE in rats treated with antibodies against ICAM-1. This finding was in line with a significantly reduced number of T-cells in the medulla. However, the number of activated macrophages and the distribution of albumin did not differ from untreated AT-EAE animals. The histological findings are in agreement with the MRI data before and after Gd-DTPA injection which were similar in treated and untreated AT-EAE rats on day 3 and 5. On day 7 after Gd-DTPA injection there was evidence of a delayed breakdown of the BBB in the treated rats. The observation of a dissociation of clinical and MRI findings, especially evidence of Gd-enhancement despite clinical improvement, may be important in the context of interpreting MRI studies in MS patients in treatment trials.

Some functions of primary auditory cortex in learning and memory formation.

In the primary auditory field AI of gerbil auditory cortex, aversive tone conditioning paradigms reshaped frequency receptive fields of single units and also changed the spatial representation of tones in fluoro-2-deoxyglucose (FDG) experiments. As another aspect of learning-induced plasticity in gerbil AI, antibodies against the immediate early gene product c-Fos identified an unusual spatial pattern of neurons in terms of a "macrocolumn." The pattern resulted from repeated short exposure of the animals to a tone in a new environment. The search for transmitters that may mediate this gene activation is carried out by microdialysis through chronically implanted probes in auditory cortex. So far, dopamine transmission was found to reflect specific aspects of auditory learning in cortex. The results suggest that spectral features of sounds as well as aspects of learned behavioral meaning of the sounds may be represented in AI.

Failure of anti-GM1 IgG or IgM to induce conduction block following intraneural transfer.

In order to confirm the reported pathogenicity of human antibodies to monosialoganglioside GM1, immunoglobulin fractions with high anti-GM1 IgG or IgM titers were prepared from patients with Guillain-Barré syndrome and multifocal motor neuropathy respectively. These fractions were injected intraneurally into rat tibial nerves with fresh human complement. Neither the anti-GM1 IgG nor the anti-GM1 IgM fraction induced significant focal conduction block or slowing compared to a pooled fraction prepared from 5 normal individuals. In contrast, rabbit experimental allergic neuritis serum included as a positive control was highly active. Transverse sections of injected nerve failed to show evidence of demyelination. Staining for human immunoglobulin in cryostat sections showed the presence of injected anti-GM1 antibody bound to nodes of Ranvier up to 6 days following intraneural transfer. These data fail to confirm previous reports of conduction block from intraneural transfer of anti-GM1 serum and suggest that such electrophysiological effects may be the result of factors other than or in addition to anti-GM1 antibodies.

In vivo MRI and its histological correlates in acute adoptive transfer experimental allergic encephalomyelitis. Quantification of inflammation and oedema.

In vivo proton MRI was carried out on a 7 Tesla system at 2-3 day intervals over 10 days in rats with adoptive transfer experimental allergic encephalomyelitis (AT-EAE), an animal model of some aspects of multiple sclerosis. In order to assess the integrity of the blood-brain barrier (BBB), MRI was performed by acquiring quantitative MR-relaxation time T1 images of the AT-EAE rat brain before and after i.v. injection gadolinium-diethylene triaminepentaacetic acid (Gd-DTPA) using an ultrafast MRI technique. The MRI findings were compared with the immunohistochemical stain of T cells, macrophages and albumin and, in addition, apoptosis of T cells was assessed using in situ nick translation (ISNT). Prior to injection of Gd-DTPA, an increase of T1 times in the brain of the AT-EAE rats was observed, which paralleled the time course of albumin in histological sections. These were MRI findings observed well before the onset of major cellular infiltration and before the onset of clinical signs. After i.v. injection of Gd-DTPA the observed decrease of T1 times paralleled macrophage activation, and less closely 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 lesion, inflammatory infiltrates and vasogenic oedema.

Expression and characterization of the chemokine receptors CCR2 and CCR5 in mice.

The chemokine receptors CCR2 and CCR5 play important roles in the recruitment of monocytes/macrophages and T cells. To better understand the role of both receptors in murine models of inflammatory diseases and to recognize potential problems when correlating these data to humans, we have generated mAbs against murine CCR2 and CCR5. In mice CCR2 is homogeneously expressed on monocytes and on 2--15% of T cells, closely resembling the expression pattern in humans. In contrast to humans, murine NK cells are highly CCR5 positive. In addition, CCR5 is expressed on 3--10% of CD4 and 10--40% of CD8-positive T cells and is weakly detectable on monocytes. Using a model of immune complex nephritis, we examined the effects of inflammation on chemokine receptor expression and found a 10-fold enrichment of CCR5(+) and CCR2(+) T cells in the inflamed kidneys. The activity of various chemokines and the antagonistic properties of the mAbs were measured by ligand-induced internalization of CCR2 and CCR5 on primary leukocytes. The Ab MC-21 (anti-CCR2) reduced the activity of murine monocyte chemotactic protein 1 by 95%, whereas the Ab MC-68 (anti-CCR5) blocked over 99% of the macrophage-inflammatory protein 1alpha and RANTES activity. MC-21 and MC-68 efficiently blocked the ligand binding to CCR2 and CCR5 with an IC(50) of 0.09 and 0.6--1.0 microg/ml, respectively. In good correlation to these in vitro data, MC-21 almost completely prevented the influx of monocytes in thioglycollate-induced peritonitis. Therefore, both Abs appear as useful reagents to further study the role of CCR2 and CCR5 in murine disease models.