Antigen-Induced Immunomodulation in the Pathogenesis of Atherosclerosis

Atherosclerosis is a chronic inflammatory disorder characterised by the accumulation of monocytes/macrophages, smooth muscle cells, and lymphocytes within the arterial wall in response to the release of proinflammatory molecules. Such accumulation results in the formation of the atherosclerotic plaque, which would eventually evolve to complications such as total artery occlusion, rupture, calcification, or aneurysm. Although the molecular mechanism responsible for the development of atherosclerosis is not completely understood, it is clear that the immune system plays a key role in the development of the atherosclerotic plaque and in its complications. There are multiple antigenic stimuli that have been associated with the pathogenesis of atherosclerosis. Most of these stimuli come from modified self-molecules such as oxidised low-density lipoproteins (oxLDLs), beta2glycoprotein1 (β2GP1), lipoprotein a (LP(a)), heat shock proteins (HSPs), and protein components of the extracellular matrix such as collagen and fibrinogen in the form of advanced glycation-end (AGE) products. In addition, several foreign antigens including bacteria such as Porphyromonas gingivalis and Chlamydia pneumoniae and viruses such as enterovirus and cytomegalovirus have been associated with atherosclerosis as potentially causative or bystander participants, adding another level of complexity to the analysis of the pathophysiology of atherosclerosis. The present review summarises the most important scientific findings published within the last two decades on the importance of antigens, antigen stimulation, and adaptive immune responses in the development of atherosclerotic plaques

Immunomodulation of Atherosclerosis Using Dendritic Cells.

Inflammation plays a crucial role in atherosclerotic plaque generation/progression. Dendritic cells (DCs), cellular immune-response components linking innate and adaptive immune systems, have been found in atherosclerotic plaques. In this study, DCs were examined as a possible therapeutic tool to modulate the inflammatory immune response underlying plaque formation. Apolipoprotein (apo) B-100 derived antigens are believed to modulate humoral immune responses to achieve atheroprotection, but their role in cellular immunity remains unclear. Therefore, one objective was to characterise the immunomodulatory effect of apoB-100-derived peptides (P2, P45, P210) on immature DCs (iDCs) and naive T lymphocytes in vitro. iDCs were generated from bone-marrow progenitor-cells of male apoE-/- mice. Peptide up-take and processing was studied by confocal microscopy after 6h, 24h and 48h. Peptide P45 was found in the endolysosomal compartments, co-localising with MHC-I and MHC-II antigen-presenting complexes. The phenotypic and differentiation characteristics of P2, P45 and P210-loaded DCs were studied by flow cytometry, and cytokine and matrix metalloproteinase production by PCR/ELISA after 48h. Proliferation and differentiation of T lymphocytes driven by peptide-loaded DCs was also studied. Peptide-loaded DCs displayed a tolerogenic phenotype similar to that of unloaded, iDCs, and inhibited CD4+ proliferation induced by mature DCs when co-cultured. My results suggest that the protective effect of the peptides could be mediated by DCs presenting them to T cells. A second objective was to examine the effect of vaccination with tolerogenic DCs (tolDCs), generated in vitro through incubation with IL-10 and TGF-B for 6 days, on atherosclerotic progression in apoE-/- mice. This showed that immunisation with tolDCs increased the number of CD8+CD25-FoxP3+ T regulatory cells as well as secretion of IL-10 within the spleen of immunised mice. IL-10 levels were also elevated in the serum, while cholesterol levels were reduced, although plaque size remained unchanged. These results provide new insights for treatment and prevention of atherosclerosis through vaccination. FUNDING: British Heart Foundation and the University of Surrey

Immunomodulation of Atherosclerosis Using Dendritic Cells.

Inflammation plays a crucial role in atherosclerotic plaque generation/progression. Dendritic cells (DCs), cellular immune-response components linking innate and adaptive immune systems, have been found in atherosclerotic plaques. In this study, DCs were examined as a possible therapeutic tool to modulate the inflammatory immune response underlying plaque formation. Apolipoprotein (apo) B-100 derived antigens are believed to modulate humoral immune responses to achieve atheroprotection, but their role in cellular immunity remains unclear. Therefore, one objective was to characterise the immunomodulatory effect of apoB-100-derived peptides (P2, P45, P210) on immature DCs (iDCs) and naive T lymphocytes in vitro. iDCs were generated from bone-marrow progenitor-cells of male apoE-/- mice. Peptide up-take and processing was studied by confocal microscopy after 6h, 24h and 48h. Peptide P45 was found in the endolysosomal compartments, co-localising with MHC-I and MHC-II antigen-presenting complexes. The phenotypic and differentiation characteristics of P2, P45 and P210-loaded DCs were studied by flow cytometry, and cytokine and matrix metalloproteinase production by PCR/ELISA after 48h. Proliferation and differentiation of T lymphocytes driven by peptide-loaded DCs was also studied. Peptide-loaded DCs displayed a tolerogenic phenotype similar to that of unloaded, iDCs, and inhibited CD4+ proliferation induced by mature DCs when co-cultured. My results suggest that the protective effect of the peptides could be mediated by DCs presenting them to T cells. A second objective was to examine the effect of vaccination with tolerogenic DCs (tolDCs), generated in vitro through incubation with IL-10 and TGF-B for 6 days, on atherosclerotic progression in apoE-/- mice. This showed that immunisation with tolDCs increased the number of CD8+CD25-FoxP3+ T regulatory cells as well as secretion of IL-10 within the spleen of immunised mice. IL-10 levels were also elevated in the serum, while cholesterol levels were reduced, although plaque size remained unchanged. These results provide new insights for treatment and prevention of atherosclerosis through vaccination. FUNDING: British Heart Foundation and the University of Surrey