The atheroprotective effect of 17beta-estradiol depends on complex interactions in adaptive immunity

Estradiol prevents fatty streak formation in chow-fed atherosclerosis-prone apolipoprotein E (ApoE)-deficient mice. We previously reported that fatty streak development of immunodeficient ApoE(-/-)/recombination activating gene 2 (RAG-2(-/-)) double-deficient mice was insensitive to estradiol. In the present work, we demonstrate that the reconstitution of ApoE(-/-)/RAG-2(-/-) with bone marrow from immunocompetent ApoE(-/-)/RAG-2(+/+) mice restores the protective effect of estradiol on fatty streak constitution. We extended this demonstration to the model of low-density lipoprotein receptor-deficient mice, establishing the obligatory role of mature lymphocytes in this process. We then investigated whether the protective effect of estradiol was mediated by a specific lymphocyte subpopulation by studying the hormonal effect on fatty streak constitution in recently developed models of ApoE(-/-) mice deficient in selective T-lymphocyte subsets (either TCRalphabeta+, CD4+, CD8+, or TCRgammadelta+ lymphocytes) or B lymphocytes. In all these specifically immunodeficient mice, estradiol administration to ovariectomized mice conferred protection as in immunocompetent ApoE(-/-) mice, clearly demonstrating that no single lymphocyte subpopulation was specifically required for this effect. These results point to additional lymphocyte-dependent mechanisms such as modulating the interactions among lymphocytes and between lymphocytes and endothelial and/or antigen-presenting cells.     

Innate immunity, macrophage activation, and atherosclerosis

Summary:  Inflammation underpins the development of atherosclerosis. Initiation and progression of vascular inflammation involves a complex cellular network, with macrophages as major contributors. Activated macrophages produce proinflammatory mediators, bridge innate and adaptive immunity, regulate lipid retention, and participate directly in vascular repair and remodeling. Recent efforts to elucidate molecular mechanisms involved in the regulation of vascular inflammation in atherosclerosis have implicated several families of innate immune recognition receptors in inflammatory activation during the course of this disease. This article reviews our current understanding of innate immune recognition receptors, signaling pathways, and putative ligands implicated in activation of macrophages in the disease. In its final section, we propose a model for the role of macrophages in bridging inflammation and atherosclerosis from the perspective of innate immune recognition and activation.     

Construction and characterization of affibody-Fc chimeras produced in Escherichia coli

Affibody-Fc chimeras were constructed by genetic fusion between different affibody affinity proteins with prescribed specificities and an Fc fragment derived from human IgG. Using affibody ligands previously selected for binding to respiratory syncytial virus (RSV) surface protein G and Thermus aquaticus (Taq) DNA polymerase, respectively, affibody-Fc fusion proteins showing spontaneous Fc fragment-mediated homodimerization via disulfide bridges were produced in Escherichia coli and affinity purified on protein A Sepharose from bacterial periplasms at yields ranging between 1 and 6 mg/l culture. Further characterization of the chimeras using biosensor technology showed that the affibody moieties have retained high selectivities for their respective targets after fusion to the Fc fragment. Avidity effects in the target binding were observed for the affibody-Fc chimeras compared to monovalent affibody fusion proteins, indicating that both affibody moieties in the chimeras were accessible and contributed in the binding. Fusion of a head-to-tail dimeric affibody moiety to the Fc fragment resulted in tetravalent affibody constructs which showed even more pronounced avidity effects. In addition, the Fc moiety of the chimeras was demonstrated to be specifically recognized by anti-human IgG antibody enzyme conjugates. One application for this class of "artificial antibodies" was demonstrated in a western blotting experiment in which one of the anti-RSV surface protein G affibody-Fc chimeras was demonstrated to be useful for specific detection of the target protein in a complex background consisting of a total E. coli lysate. The results show that through the replacement of the Fab portion of an antibody for an alternative binding domain based on a less complicated structure, chimeric proteins compatible with bacterial production routes containing both antigen recognition domains and Fc domains can be constructed. Such "artificial antibodies" should be interesting alternatives to, for example, whole antibodies or scFv-Fc fusions as detection devices and in diagnostic or therapeutic applications.     

Introduction of a new hepatitis agent in retrospect: genetic studies of Swedish hepatitis D virus strains.

The supposedly first outbreak of hepatitis D virus (HDV) infection in Sweden occurred among intravenous drug addicts in the Malmö area in the mid-1970s. Stored sera from this outbreak were used for viral RNA extraction and analysis. By sequence comparisons, the HDV genomes from those Swedish patients fell into two separate clusters, within which the RNA sequences were closely related. These two HDV groups genetically resembled the French and US-1 isolates of genotype I, respectively, indicating that there had been at least two separate sources of HDV infection. The genetic alterations of the HDV RNA were investigated by sequence analysis of nine annually drawn serum samples from one patient and paired samples collected between 2 and more than 10 years apart from six patients with chronic HDV infection. Only mutational changes were observed, and no insertion or deletion appeared throughout the periods observed. It was found that the Swedish HDV isolates mutationally evolved at an average rate of 1.1 x 10(-3) substitutions per nucleotide per year over a long time course of chronic HDV infection, which is of the same magnitude as that of other RNA viruses.     

Effects of subacute treatment with toluene on cerebrocortical alpha- and beta-adrenergic receptors in the rat. Evidence for an increased number and a reduced affinity of beta-adrenergic receptors

Subacute treatment with toluene (80-1500 p.p.m.) produces a dose-dependent reduction of affinity and increase in density of the beta-adrenergic antagonist [3H]dihydroalprenolol binding sites in the frontoparietal cortex of the male rat, while the binding characteristics of alpha 1-adrenergic ([3H]WB 4101) and alpha 2-adrenergic ([3H]p-aminoclonidine) binding sites in the same region is unaffected by this treatment as evaluated in vitro. Therefore, it is suggested that the cortical beta-adrenergic receptors are particularly vulnerable to the action of toluene in vivo. It is speculated that as a result cortical beta-adrenergic neurotransmission may be altered following exposure to low concentrations of toluene, possibly related to the physico-chemical properties of toluene, leading to changes in membrane fluidity.     

Transforming growth factor-beta (TGF-beta) and tissue transglutaminase expression in the small intestine in children with coeliac disease

The production of cytokines from T cells and macrophages is of potential importance for the histological changes apparent in coeliac disease (CoD). Small intestinal biopsy specimens from children with CoD and disease control subjects were investigated for their content of cytokines and tissue transglutaminase (tTG). The transforming growth factor-beta1 (TGF-beta1) expression was increased in the lamina propria of children with villous atrophy. In contrast, TGF-beta3 was expressed at a higher level in the epithelium and the lamina propria of the disease control subjects. The tTG expression was increased in the small intestine of CoD patients as compared with that in subjects. Interleukin-4 (IL-4) was detected in the lamina propria of both CoD patients and controls, and some of the investigated biopsy specimens also showed IL-4 expression in the epithelium. We conclude that children with active CoD could have an altered expression of TGF-beta and tTG in the small intestine and that a disturbed regulation of TGF-beta may be of importance in the immune pathogenesis of CoD.     

Ultrastructural studies on the localization of IgG in the aortic endothelium and subendothelial intima of atherosclerotic and nonatherosclerotic rabbits

Immunoelectron microscopy with peroxidase-conjugated Fab fragments of anti-IgG was used for studying the localization of IgG in the aortic endothelium and subendothelial intima of atherosclerotic and nonatherosclerotic rabbits. Small amounts of IgG were found in the cell coat, in caveolae and vesicles, and also in intercellular clefts of endothelial cells from normocholesterolemic rabbits. Injured endothelial cells exhibited prominent accumulations of IgG in the cytoplasmic matrix, possibly due to leakage through plasma membrane defects. In atherosclerotic lesions from hypercholesterolemic rabbits, there was a striking increase in the amount of IgG-reactive material in the cell coat and vesicles of intact endothelial cells. Also in these animals, injured endothelial cells were characterized by a cytoplasmic IgG accumulation. There were prominent IgG depositions in the subendothelial zone of the lesions. IgG was adhering to collagen fibers, and also coating the surfaces of subendothelial foam cells. The pathophysiological significance of an interaction between such intimal IgG and phagocytes is discussed.