In K/BxN T cell receptor-transgenic mice, spontaneous inflammatory arthritis exhibiting many of the features of human rheumatoid arthritis (RA) is initiated by T cells, but is almost entirely sustained by antibodies to the self-antigen glucose-6-phosphate isomerase (GPI). The relevance of these observations to human disease has been questioned. Here we show that 64% of humans with RA, but not controls, had increased concentrations of anti-GPI immunoglobulin G (IgG) in serum and synovial fluid. In addition, the concentrations of soluble GPI in the sera and synovial fluids of RA patients were also elevated, which led to immune complex formation. Using phage-display methods, we cloned a panel of specific high-affinity human monoclonal anti-GPI IgGs from a patient with RA. These antibodies were highly somatically mutated, which was indicative of an affinity-matured response that was antigen driven. Immunohistochemistry of RA synovium showed high concentrations of GPI on the surface of the synovial lining and on the endothelial cell surface of arterioles; this indicated a mechanism by which antibodies to GPI may precipitate joint disease. The results indicate that the immunological events that lead to the development of autoimmune disease in the K/BxN mouse model may also occur in human RA. This data may be used to develop new strategies for therapeutic intervention.

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Direct interaction between endogenous cellular prion protein (PrP C ) and misfolded, disease-associated (PrP Sc ) conformers is a key event in prion propagation, which precedes templated conversion of PrP C into nascent PrP Sc and prion infectivity. Although almost none of the molecular details of this pivotal process are understood, the persistence of individual prion strains suggests that assembly of the prion replicative complex is mechanistically precise. To systematically map defined regions of PrP C sequence that bind tightly to PrP Sc , we have generated a

Transmissible spongiform encephalopathies, including variant-Creutzfeldt-Jakob disease (vCJD) in humans and bovine spongiform encephalopathies in cattle, are fatal neurodegenerative disorders characterized by protein misfolding of the host cellular prion protein (PrPC) to the infectious scrapie form (PrPSc). However, the mechanism that exogenous PrPSc infects cells and where pathologic conversion of PrPC to the PrPSc form occurs remains uncertain. Here we report that similar to the mechanism of HIV-1 TAT-mediated peptide transduction, processed mature, full length PrP contains a conserved N-terminal cationic domain that stimulates cellular uptake by lipid raft-dependent, macropinocytosis. Inhibition of macropinocytosis by three independent means prevented cellular uptake of recombinant PrP; however, it did not affect recombinant PrP cell surface association. In addition, fusion of the cationic N-terminal PrP domain to a Cre recombinase reporter protein was sufficient to promote both cellular uptake and escape from the macropinosomes into the cytoplasm. Inhibition of macropinocytosis was sufficient to prevent conversion of PrPC to the pathologic PrPSc form in N2a cells exposed to strain RML PrPSc infected brain homogenates, suggesting that a critical determinant of PrPC conversion occurs following macropinocytotic internalization and not through mere membrane association. Taken together, these observations provide a cellular mechanism that exogenous pathological PrPSc infects cells by lipid raft dependent, macropinocytosis.

We identified a major linear epitope of C1q that is the target of anti-C1q in SLE. The ELISA using this peptide was more specific and more sensitive than a conventional anti-C1q assay for the detection of active nephritis in SLE patients.