Multiple sclerosis (MS), a chronic demyelinating disease, is thought to be initiated by pathogenic T cells that transmigrate the vascular endothelium and enter the brain through vascular and parenchymal basement membranes (BM). Vaccination with T-cell lines reactive with myelin basic protein (MBP) and myelin oligodendrocytic glycoprotein (MOG) epitopes, expanded with interleukin-2 (IL-2), and attenuated by ionizing radiation is currently being evaluated as a therapeutic modality for this disease. We examined mechanisms potentially involved in pathogenic cell migration into the central nervous system (CNS) and the influence of irradiation on these processes. Seven of 7 autoantigen-responsive T-cell lines from MS patients adhered to collagen IV, the major collagenous constituent of BMs. This adhesion was inhibited almost completely by monoclonal antibody (MAb) to very late antigen (VLA)-1 and partially by anti-VLA-2. T-cell lines from healthy donors adhered more variably to collagen IV. Furthermore, patient derived T cells actively transmigrated through a collagen IV gel toward medium containing TNF-a, in a process that was inhibited by MAbs to VLA-1. Ionizing radiation at the dose used in vaccine preparation, inhibited morphological polarization associated with migratory capability, induced integrin clustering on the cell membrane, and abrogated adhesion to collagen IV. These findings may have important implications for understanding the pathogenesis of MS and how irradiation of potentially pathogenic T cells produces a reagent with possible therapeutic effects in T-cell vaccination (TCV).