VLA-4 expression on peripheral blood lymphocytes is downregulated after treatment of multiple sclerosis with interferon beta zy P.A. Calabresi, MD; C.M. Pelfrey, PhD; L.R. Tranquill, MS; H. Maloni, RN; and H.F. McFarland, MD Article abstract-Adhesion molecules are likely to play a critical role in the immunopathogenesis of multiple sclerosis (MS). The interaction of vascular cell adhesion molecule-1 (VCAM-1) with its lymphocyte ligand very late antigen-4 (VLA-4)may mediate migration of lymphocytes into the CNS. We have previously demonstrated that MS patients treated with interferon beta (IFN-P) have a significant increase in soluble VCAM-1 (sVCAM-1) soon after the initiation of treatment, and this effect correlated with the resolution of contrast-enhancing MRI lesions. We studied the cell surface expression of VLA-4 by flow cytometry in 10 MS patients before and during IFN-p treatment. We found a significant decrease in mean VLA-4 fluorescence of MS patients' lymphocytes on treatment and no change in untreated controls. In vitro treatment of lymphocytes with IFN-P did not reproduce this effect, but the addition of sVCAM-1 did result in a decrease in VLA-4 expression. These data indicate that the previously identified increase in sVCAM-1 may lead to a decrease in VLA-4 expression and that this effect may partially explain the mechanism of action of IFN-P. NEUROLOGY 1997;49:1111-1116 Multiple sclerosis (MS) is an immune-mediated de- myelinating disease of the CNS.l Several lines of evidence suggest that activated T cells in the periph- ery migrate into the CNS, where they mediate the inflammatory re~ponse.~*~ The process by which T cells cross the cerebral vascular endothelium is just beginning to be elucidated and likely involves nu- merous cytokines and adhesion m01ecules.~-~ The cy- tokines tumor necrosis factor alpha (TNFa) and in- terferon gamma (IFN-y) induce expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion mol- ecule (VCAM-l) on the surface of the e n d ~ t h e l i u m . ~ ~ ~ The respective ligands of these molecules, lympho- cyte function antigen-1 (LFA-1) and very late antigen-4 (VLA-41, are present on most lymphocytes and other mononuclear cells. The interaction be- tween the immunoglobulin superfamily members (ICAM-1 and VCAM-1) on the vascular endothelium and the integrins (LFA-1 and VLA-4) on the lympho- cytes allows firm adhesion of cells to cerebral vascu- lar endothelium and ultimately migration into the CNS.g.'o It has been recently hypothesized that these molecules may play a critical role in the immuno- pathogenesis of the MS Magnetic resonance imaging with contrast en- hancement is an excellent clinical tool for measuring the extent of blood-brain barrier (BBB) permeability in MS patient^.'^ Focal areas of BBB breakdown can be quantified on contrast-enhanced MRIs and have been shown to correlate with clinical disease activity and early path~logy.'~-l~ Contrast-enhanced MRI is now used as a measure of drug efficacy in clinical trials.I7 Interferon beta (IFN-P) modestly reduces the severity and frequency of clinical exacerbations and markedly diminishes T2-weighted and contrast- enhanced MRI activity.18-20 The mechanism by which BBB integrity is restored remains unknown, but the effect likely involves modification of cytokines or ad- hesion molecules, or both. We recently demonstrated that MS patients treated with IFN-p have a significant elevation of soluble VCAM-1 (sVCAM-1)in the serum, which cor- related with the reduction in contrast-enhanced MRI lesions.21 The mechanism for this elevation is un- clear but may involve direct cleavage of cerebral vas- cular endothelial cell surface VCAM-1 into the se- rum or may occur secondary to a decrease in VLA-4 expression leading to an increased pool of sVCAM-1. We now report a downregulation of VLA-4 expres- sion on CD3+ peripheral blood mononuclear cells (PBMCs) after treatment with IFN-P in vivo, but not in vitro. In vitro treatment of PBMCs with recombi- nant sVCAM-1 (rsVCAM-1) reproduced the down- regulation of VLA-4 seen in vivo, which suggests a From the Neuroimmunology Branch (Dr. Calahresi, L. Tranquill, H. Maloni, and Dr. McFarland), National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD; and the Department of Pathology (Dr. Pelfrey), Case Western Reserve University, Cleveland, OH. H.F.M. has received honoraria as an unconditional educational grant from Berlex. None of the investigators has any pertinent financial interest in Berlex. Received November 25, 1996. Accepted in final form April 24, 1997. Address correspondence and reprint requests to Dr. P.A. Calahresi, Neuroimmunology Branch, NINDS, National Institutes of Health, Building 10, Room 5b-16, 10 Center Drive MSC-1400, Bethesda, MD 20892-1400. Copyright zyxwvu 0 1997 by the American Academy of Neurology zy 1111