The interrelationship of α4 integrin and matrix metalloproteinase-2 in the pathogenesis of experimental autoimmune encephalomyelitis

Previous studies have suggested that surface expression of alpha 4 integrin by autoreactive T-cell clones is necessary for the clones to induce experimental autoimmune encephalomyelitis (EAE), a mouse model for human multiple sclerosis. To provide direct evidence for this phenomenon, we have transfected alpha 4 integrin into C19 alpha 4-LO, a myelin basic protein-reactive T-cell clone that does not express alpha 4 integrin and does not induce EAE when adoptively transferred into a susceptible mouse strain. Transfection of alpha 4 integrin converted this clone to an alpha 4 integrin-expressing clone that induced EAE. We then examined potential mechanisms by which alpha 4 integrin may facilitate the disease process. C19 T-cell clones adhered equally to a monolayer of microvascular endothelial cells, regardless of level of alpha 4 integrin expression. However, in contrast to T-cell clones that do not express alpha 4 integrin, T-cell clones that express alpha 4 integrin (endogenously or by transfection) transmigrated through an endothelial cell layer and subendothelial matrix at an enhanced rate and adhered to recombinant vascular cell adhesion molecule-1 (rVCAM-1) and the CS1 fragment of fibronectin, and after adhesion to these ligands, a matrix-degrading metalloproteinase (MMP-2) was induced and activated. The clones were also shown to constitutively express the membrane-type matrix metalloproteinase (MT1-MMP), an enzyme that activates MMP-2. GM6001 and UK-221,316, inhibitors of metalloproteinases, reduced alpha 4 integrin-mediated transmigration and EAE induction by C19 T-cell clones. in addition, we studied a second EAE-inducing T-cell clone, MM4, which constitutively expresses alpha 4 integrin and MMP-2. Engagement of alpha 4 integrin on the MM4 clone up-regulated the expression and activation of MMP-2, without changing the expression of MT1-MMP. MMP inhibitors also reduced transmigration of and EAE induction by the MM4 T-cell clone. These studies demonstrate directly that expression of alpha 4 integrin by autoreactive T-cell clones is required for adoptive transfer of EAE in this model. We also define a role for alpha 4 integrin in the disease process in mediating the induction and coordinate activation of a matrix metalloproteinase (MMP-2), which facilitates T-cell transmigration.