Bacterial genomic DNA, plasmid DNA (pDNA) and synthetic oligodeoxynucleotides (ODN) containing immunostimulatory DNA sequences (ISS) have been proposed to foster a Th1 response via the release of type 1 cytokines from macrophages, dendritic cells, NK cells and B cells. In this study, we show that ISS-enriched DNA up-regulates a distinct profile of cell surface molecules on macrophages and B cells in vitro and in vivo. ISS-ODN and ISS-containing pDNA enhanced the expression of antigen presentation molecules (MHC class I and II), co-stimulatory molecules (B7-1, B7-2 and CD40), cytokine receptors (IFN-gamma receptor and IL-2 receptor), an adhesion molecule (ICAM-1) and an Fc receptor (Fcgamma receptor) on murine B cells or bone marrow-derived macrophages. The increased expression of these surface molecules is seen in purified cell populations and is largely independent of the effects of type 1 cytokines. Splenic antigen-presenting cells stimulated with ISS-ODN in vivo efficiently activate naive T cells and bias their differentiation toward a Th1 phenotype in vitro. Thus, the induction of both type 1 cytokines and a distinct profile of cell surface molecules contributes to the potent immunostimulatory effects of ISS-containing DNA on innate and adaptive immunity.

In order to delineate the neuroprotective role of the low density lipoprotein receptor-related protein (LRP) against amyloid ␤-protein toxicity, studies were performed in C6 cells challenged with amyloid ␤-protein in the presence or absence of activated ␣ 2 -macroglobulin. Toxicity was assessed via two cell viability assays. We found that this endocytic receptor conferred protection against amyloid ␤-protein toxicity in the presence of activated ␣ 2 -macroglobulin and its down-regulation via inhibition by receptor-associated protein or transfection of cells with presenilin 1, increased susceptibility to amyloid ␤-protein toxicity. Increased surface LRP immunoreactivity in response to amyloid ␤-protein challenge was associated with increased translocation of LRP from the endoplasmic reticulum to the surface, rather than from increased mRNA or protein expression. Furthermore, this translocation of LRP to the surface was mediated by a calcium/calmodulin protein kinase II-dependent signaling pathway. These studies provide evidence for a protective role of LRP against amyloid ␤-protein toxicity and may explain the aggressive nature of presenilin-1 mutation in familial Alzheimer's disease. Low density lipoprotein (LDL)1 receptor-related protein (LRP) is a multifunctional endocytic receptor that binds a variety of ligands including apolipoprotein E (apoE)-containing lipoproteins (1, 2), activated ␣ 2 -macroglobulin (*␣ 2 m) complexes, and proteins containing Kunitz-type protease inhibitor domains such as secreted amyloid precursor protein (3). Recent studies have suggested that altered LRP regulation may be an integral component of Alzheimer's disease (AD) pathogenesis (4, 5). Importantly, LRP and its ligands, APP, apoE, and ␣ 2 m, have all been genetically linked to AD (6 -9), and colocalize in senile plaques, a hallmark of AD (4, 10). In addition, patients with probable AD have increased serum levels of LRP ligands including apoE, ␣ 1 -antichymotrypsin, plasmin, and urokinase (11-13), suggesting that LRP expression (or function) may be deficient in these patients. Furthermore, we have previously shown that overexpression of or mutations in the presenilin 1 (PS1) gene, which has been closely linked to the majority of early onset familial AD cases, results in significant down-regulation of LRP (5). Taken together, these data indicate that LRP plays a central role in AD pathogenesis.Although the mechanisms through which LRP might be involved in AD remain unclear, a recent study has suggested a role for LRP in clearance of amyloid ␤-protein (A␤) (14). Specifically, A␤ is internalized by LRP when bound to apoE or *␣ 2 m (14 -18). Whether this effect is toxic or protective is not completely known. Thus, the main objective of the present study was to determine if addition of an A␤-binding LRP ligand prevents A␤ toxicity. The results suggest that LRP mediates protection against A␤ toxicity in the presence of *␣ 2 m and that LRP surface expression is preferentially up-regulated in response to A␤ challenge via a calcium/calmod...

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