The major known genetic risk factors in multiple sclerosis reside in the major histocompatibility complex (MHC) region. Although there is strong evidence implicating MHC class II alleles and CD4(+) T cells in multiple sclerosis pathogenesis, possible contributions from MHC class I genes and CD8(+) T cells are controversial. We have generated humanized mice expressing the multiple sclerosis-associated MHC class I alleles HLA-A(*)0301 (encoding human leukocyte antigen-A3 (HLA-A3)) and HLA-A(*)0201 (encoding HLA-A2) and a myelin-specific autoreactive T cell receptor (TCR) derived from a CD8(+) T cell clone from an individual with multiple sclerosis to study mechanisms of disease susceptibility. We demonstrate roles for HLA-A3-restricted CD8(+) T cells in induction of multiple sclerosis-like disease and for CD4(+) T cells in its progression, and we also define a possible mechanism for HLA-A(*)0201-mediated protection. To our knowledge, these data provide the first direct evidence incriminating MHC class I genes and CD8(+) T cells in the pathogenesis of human multiple sclerosis and reveal a network of MHC interactions that shape the risk of multiple sclerosis.

Recent studies in this laboratory demonstrated that several sulphated polysaccharides can inhibit metastasis of the rat mammary adenocarcinoma 13762 MAT, probably by preventing the passage of tumour cells through the walls of blood vessels. In order to directly test this possibility, 13762 MAT cells were cultured with (35S)O4(=)-labelled subendothelial extracellular matrices (ECM) and ECM degradation was monitored in either the presence or absence of different sulphated polysaccharides. Degradation products were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis and subsequent autoradiography. The 5 sulphated polysaccharides that had previously been shown to possess anti-metastatic activity were potent inhibitors of the degradation of subendothelial ECM by 13762 MAT cells. In contrast, of the 4 polysaccharides tested that failed to inhibit metastasis, 3 had no effect on ECM breakdown and one (carrageenan-kappa) was substantially less effective at inhibiting ECM degradation than the anti-metastatic preparations. It was also shown that 13762 MAT cells produce a heparan sulphate-specific glycosidase (heparanase) that degrades the heparan sulphate side-chains of the ECM, the action of this enzyme rather than that of other ECM-solubilizing enzymes being inhibited by the antimetastatic sulphated polysaccharides. Additional experiments indicated that the anti-coagulant activity of the polysaccharides probably plays a minor role in their anti-metastatic effects since heparin, almost completely depleted (98-99.5%) of heparin molecules with anti-coagulant activity by passage over an anti-thrombin III column, retained its ability to inhibit 13762 MAT heparanases and was almost as effective as unfractionated heparin at inhibiting tumour-cell metastasis. Collectively, these data suggest that sulphated polysaccharides inhibit the metastasis of 13762 MAT cells by inhibiting tumour-cell-derived heparanases involved in the penetration of the vascular endothelium and its underlying basement membrane by tumour cells.