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Biomedical subjects

B Grubeck-Loebenstein

Publications and source records attributed to B Grubeck-Loebenstein.

At least 19 recordsLinked to original sources
PubMed1999

TNFalpha plus IFNgamma induce the production of Alzheimer beta-amyloid peptides and decrease the secretion of APPs.

The appearance of inflammatory markers associated with amyloid plaques indicates a state of chronic inflammation in Alzheimer's disease (AD). Multiple epidemiological studies also suggest that patients taking anti-inflammatory drugs have a decreased risk of developing AD. Here we present evidence that inflammatory cytokines can alter the metabolism of the beta-amyloid precursor protein (betaAPP). We show that the combination of tumor necrosis factor alpha and interferon gamma triggers the production of beta-amyloid peptides and inhibits the secretion of soluble APPs by human neuronal and extraneuronal cells. The results demonstrate a new mechanism by which inflammatory components can exacerbate the fundamental pathology in AD.

Alzheimer Disease↗
PubMed1998

Sex steroids do not prevent amylin-induced apoptosis in human cells.

Formation of amylin-containing islet amyloid deposits may contribute to the progressive deterioration of beta cell function in non-insulin-dependent diabetes mellitus. As diabetes mellitus occurs in male, but rarely in female transgenic mice expressing human amylin in their pancreatic beta cells, it is of interest to study the influence of estradiol (E2) and testosterone (T) on amylin-induced cytotoxicity in human cells. The insulinoma cell line CM, thyroid epithelial cells (TEC) in primary culture, and nontransformed fibroblast lines were used. The occurrence of apoptotic cell death was assessed by nuclear labeling with propidium iodide. Amylin was cytotoxic on all cell types tested, but had the most pronounced effect on TEC and the weakest on the CM cell line. Although both E2 and T decreased the proportion of apoptotic cells in cultures kept in the absence of amylin, neither of the two hormones was able to counteract amylin-induced cytotoxicity. beta cell death and hyperglycemia can thus presumably not be prevented by the neutralization of amylin effects by sex steroids.

Amyloid↗
PubMed1998

Dendritic cell responsiveness to stimulation with influenza vaccine is unimpaired in old age.

We have previously demonstrated that whole virus influenza vaccine can activate dendritic cells (DC). In the present study we analyzed whether DC activation was affected by the aging process. For this reason the expression of immunoregulatory molecules and the production of cytokines were compared in blood-derived DC from old and young healthy individuals following stimulation with inactivated influenza virus. Unstimulated DC from young and old individuals had a similar surface expression of MHC class II and CD54 and secreted moderate amounts of IL-12 and TNF-alpha. Stimulation with influenza vaccine led to a marked increase in the production of surface molecules and cytokines. These changes were equally pronounced in cells from young and old individuals. Our results demonstrate that DC responsiveness to stimulation with a viral vaccine is unimpaired in old age. DC may, therefore, represent a potent tool for immunotherapy and may increase the efficacy of vaccines in the elderly.

Adult↗
PubMed1998

Whole virus influenza vaccine activates dendritic cells (DC) and stimulates cytokine production by peripheral blood mononuclear cells (PBMC) while subunit vaccines support T cell proliferation.

Three types of trivalent influenza vaccines were analysed for their in vitro stimulatory properties on immune cells from young healthy volunteers. A whole inactivated virus (WV) vaccine, a conventional subunit (c-SU) preparation and a new virosomal subunit (v-SU) vaccine were used. Blood-derived DC up-regulated MHC class II, CD54, CD80 and CD86 after exposure to WV vaccine, indicating their functional maturation, but were only moderately affected by subunit (SU) vaccines. In addition, IL-12 and tumour necrosis factor-alpha (TNF-alpha) secretion by DC were markedly enhanced by WV, but not by SU vaccines. The production of IL-2 and interferon-gamma (IFN-gamma) by PBMC was also strongly stimulated by WV, but much less by SU vaccines, among which the v-SU vaccine was a better stimulator of IL-2 secretion. In contrast to WV vaccine both SU vaccines were powerful stimulators of PBMC proliferation. Our results suggest that the presence of influenza core components leads to the activation of DC and triggers the production of cytokines by PBMC. SU vaccines are in contrast excellent stimulators of T cell growth. A combination of WV and SU vaccines in immunization regimes might allow optimal T cell priming as well as the efficient generation and maintenance of memory cells.

Cell Division↗
PubMed1998

The production of the Alzheimer amyloid precursor protein (APP) in extraneuronal tissue does not increase in old age.

Alzheimer's disease (AD) is characterized by the cerebral deposition of beta-amyloid (A beta). A beta plaques also occur in the brains of healthy aged individuals, and A beta concentrations are increased in the cerebrospinal fluid (CSF) in old age. Based on results from an in vitro senescence model on human fibroblasts, it was proposed that the production of the beta-amyloid precursor protein (APP) was increased during aging. No information was available as to whether APP production was also augmented in aged humans. It was therefore the aim of the present study to analyze APP in connective tissue, skeletal muscle, peripheral blood mononuclear cells, and serum samples from young and aged healthy individuals. APP production was assessed by Northern and Western blotting. The expression of the different APP isoforms was studied by reverse transcription-polymerase chain reaction (RT-PCR) technique. The results demonstrate that APP messenger ribonucleic acid (mRNA) and protein concentrations were identical in blood and tissue samples from young and aged individuals and that there were no age-dependent changes in the APP isoform production pattern. Thus, our data strongly argue against the possibility of an altered production of APP during healthy aging and underline the point that in vitro aging models may not accurately reflect the in vivo situation.

Adult↗
PubMed1997

Tumor necrosis factor alpha augments amyloid beta protein (25-35) induced apoptosis in human cells.

No information is yet available on the effect of tumor necrosis factor alpha (TNFalpha) on amyloid beta protein (Abeta)-induced cytotoxicity in human cells. For this reason the induction of apoptosis by TNFalpha and Abeta (25-35) was studied in primary cultures of human thyroid and kidney cells as well as in the neuroblastoma line SK-N-SH and in DU-145 cells. Apoptosis occurred in all cell types after Abeta (25-35) treatment, but was markedly enhanced when TNFalpha was additionally present. This effect was less pronounced in transformed cell lines than in primary cultures, in which TNFalpha on its own was not cytotoxic. Apoptosis was still more prevalent under serum free culture conditions. The results demonstrate that TNFalpha may support the occurrence of Abeta-mediated cell death and thus contribute to the development of pathological changes in Alzheimer's disease (AD).

Amyloid beta-Peptides↗
PubMed1997

[Immune reaction to tetanus in the elderly: what is the duration of vaccine protection?].

Infectious diseases represent one of the most frequent causes of morbidity and mortality in the elderly. Little information is yet available on the state of immunization against well-known antigens such as tetanus toxoid (TT) in old age. It was, therefore, the aim of this study to analyze antibody titres and peripheral blood mononuclear cell (PBMC) reactivity to TT in healthy SENIEUR compatible young (< 30 years, n = 25) and old (> 65 years, n = 32) blood donors. TT-specific antibodies were measured by the ELISA technique; PBMC proliferation was assessed by 3H-thymidine incorporation analysis. In the young group TT antibody titres were detectable in all but two individuals, whereas 60% of the old persons had no detectable TT antibodies. This seemed partly to be due to a shortened immunological memory in old age, since 32% of the aged persons without TT antibodies had been vaccinated within the past 10 years, 21% even 3 to 6 years prior to investigation. TT antibody concentrations were normal in aged individuals vaccinated within the past two years. Peripheral blood lymphocytes from all but two persons without antibody titres did not proliferate when stimulated with TT in vitro, indicating that no memory T cells were available to reinduce an efficient immune response. Our results suggest that the tetanus vaccination strategy practised in Austria does not guarantee full protection in the elderly.

Adult↗
PubMed1997

Amyloid beta-protein(25-35) increases cellular APP and inhibits the secretion of APPs in human extraneuronal cells.

Amyloid beta-protein (A beta) is the core component of the senile plaques occurring during Alzheimer's disease and in its aggregated form is cytotoxic for neuronal and extraneuronal cells. In this study, the influence of the spontaneously aggregating fragment A beta(25-35) on the expression and metabolism of beta-amyloid precursor protein (APP) was investigated in human extraneuronal cells. Cellular extracts and conditioned supernatants were analyzed by immunoblotting. A beta(25-35) strongly increased the cellular content of APP in cultured epithelial cells from thyroid glands and kidneys as well as in the promyelogranulocytotic cell line HL-60. At the same time A beta reduced the secretion of soluble APPs to less than one-third of its control value, but did not alter the secretion of fibronectin, which was used as a control protein. Despite these changes, APP transcription was not changed following A beta(25-35) treatment. These results demonstrate that A beta(25-35) strongly increases the APP content of extraneuronal cells by inhibiting its secretory processing. This may result in a deviation of APP metabolism towards an internal, potentially amyloidogenic pathway.

Adult↗
PubMed1997

Changes in the aging immune system.

The functional capacity of the immune system gradually declines with age. T lymphocytes are more severely affected than B cells or antigen-presenting cells. This is mainly due to the involution of the thymus which is almost complete at the age of 60. The host is then dependent on the T cell pool generated in earlier life. Continuous activation, clonal expansion and elimination of T cells of various specificities eventually leads to changes in the T cell repertoire. CD45RA+ "naive" cells are replaced by CD45RA- "memory" cells and a T cell receptor oligoclonality develops. At the same time, T cells with signal transduction defects accumulate. Age-related T cell alterations lead to a decreased clonal expansion and a reduced efficiency of T cell effector functions such as cytotoxicity or B cell help. Decreased antibody production and a shortened immunological memory are the consequence. Changes in the aging immune system represent a permissive factor for the frequent occurrence and the severity of disease. Efficient protection of elderly individuals by suitable vaccination strategies is therefore a matter of great importance.

Aging↗
PubMed1997

Peripheral blood dendritic cells reinduce proliferation in in vitro aged T cell populations.

Dendritic cells (DC) are professional antigen presenting cells which are essential for the initiation of an immune response. Recently we demonstrated that DC, which had been propagated from the peripheral blood of healthy elderly people, were morphologically and functionally intact. It was the aim of the present study to analyze how DC from young and old healthy individuals could affect T cell responsiveness to antigen in an in vitro senescence model. Tetanus toxoid (TT)-specific T cell lines were derived from 3 young (< 30 years) and 3 old (> 65 years) individuals and were kept in long term culture. T cell proliferation in response to stimulation with antigen presented by either autologous peripheral blood mononuclear cells (PBMC) or DC was assessed at three different time points, once soon after the initiation of the cultures and twice after 20 to 30 population doublings at a stage when growth, was slow and programmed cell death imminent. Antigen presentation by DC enhanced T cell proliferation at each time point and reinduced proliferation in in vitro aged T cell populations which had stopped dividing. Terminal apoptosis was thus prevented. DC from old individuals were as effective as cells from young donors. Our results demonstrate that DC stimulate the clonal expansion and postpone the clonal elimination of antigen-specific T cell populations. As a consequence they may increase immunoreactivity, prolong immunological memory and be of particular importance for the maintenance of the T cell repertoire in old age.

Adult↗
PubMed1997

Interactions of the Alzheimer beta amyloid fragment (25-35) with peripheral blood dendritic cells.

We have previously demonstrated that soluble amyloid beta protein (A beta) induces IL-2 receptor expression and proliferation in peripheral T cells from young and old healthy individuals, but not from patients with Alzheimer's disease (AD). It seemed of interest to examine how the immune system would react upon stimulation with A beta in its aggregated form. It was the aim of this study to define interactions between the spontaneously aggregating A beta (25-35) and antigen-presenting cells. Human dendritic cells (DC), propagated from the peripheral blood of young healthy individuals, were incubated with A beta (25-35) and its effects on DC survival, cytokine release, and surface marker expression were monitored. The question whether DC could present amyloid to T cells was also addressed. We demonstrated that A beta (25-35) does not induce DC apoptosis or necrosis. This was shown by electron microscopy as well as by nuclear staining with propidium iodide. Some peptide aggregates were found in intracellular vacuoles of DC. This process did not increase production of TNF alpha and did not change the surface expression of CD18, CD11a or CD11b. A decreased surface expression of MHC class II molecules was, however, noted. DC pulsed with A beta aggregates were unable to stimulate T cells in an autologous coculture system. The results demonstrate that amyloid may escape immune recognition by its failure to activate antigen-presenting cells and by inhibiting MHC class II surface expression.

Adult↗
PubMed1997

Primary and secondary alterations of immune reactivity in the elderly: impact of dietary factors and disease.

The function of the immune system declines with age. It is the aim of the present review to demonstrate that it makes sense to distinguish between primary and secondary alterations of immune reactivity in the elderly. Primary changes occur as the result of an age-dependent intrinsic decline of immune responsiveness. They also occur in healthy persons, i.e. persons selected according to the criteria of the SENIEUR protocol of the European Community's Concerted Action Program on Aging (EURAGE). T lymphocytes are hereby more severely affected than B cells or antigen presenting cells, possibly due to the involution of the thymus, which is almost complete at the age of 60. Secondary immunological changes occur as the result of environmental factors including diet, drug intake, physical activity etc. or are alternatively due to underlying diseases. In this article, the effects of high lipid intake as well as the impact of diseases, such as for instance Alzheimer's disease and atherosclerosis, will be addressed. The results underline the complexity of immunological alterations to be expected in old age. Changes in the aging immune system represent an opportunity for increased frequency and severity of disease and endanger the protective effect of vaccination.

Aged↗
PubMed1997

Cytokine production in response to stimulation with tetanus toxoid, Mycobacterium tuberculosis and influenza antigens in peripheral blood mononuclear cells and T cell lines from healthy elderlies.

Little is known about the type 1/type 2 T cell dichotomy in old age. Peripheral blood mononuclear cells (PBMC) and T cell lines from old and young healthy individuals were therefore analyzed for their production of interferon gamma (IFN-gamma) and interleukin 4 (IL-4). Tetanus toxoid (TT), purified protein derivative of Mycobacterium tuberculosis, inactivated influenza virus and OKT-3 were used as stimuli. RT-PCR and ELISA determinations were performed. When stimulated with TT, PBMC from young and old individuals expressed IL-4, but produced little IFN-gamma. All other stimuli induced a pronounced IFN-gamma production, while little or no IL-4 was expressed. T cell lines, regardless of their specificity or the donor age, produced IFN-gamma and IL-4. The quantities of cytokines produced did not significantly differ between the age groups. The capacity of the immune system to trigger type 1 and type 2 T cell responses is thus well preserved in old age.

Adult↗
PubMed1996

T cells from rejected human kidney allografts respond to heat shock protein 72.

The immune response to heat shock proteins (hsps) is gaining more and more interest. Members of the 65 and the 70 kDa hsp families have been shown to be target molecules of the immune system in autoimmune diseases, in cancer immunity and recently in the rejection of rat heart allografts. It was therefore the aim of the present study to investigate whether T cells propagated from two rejected human renal allografts also recognised hsps. In vivo activated interleukin-2 (IL-2) receptor positive T cells were expanded from renal allografts, which had been removed because of irreversible rejection, by 1 week of culture in IL-2 only, followed by stimulation with OKT-3 in combination with IL-2. One T cell line was obtained from each graft. FACS analysis of the lines demonstrated that 51% and 53% of the cells were CD4+ and 45% and 42% CD8+; 4% and 5% were gamma delta + T cells. Both lines had a significant proliferative response when stimulated with recombinant human hsp 72. In contrast, hsp 65 did not induce stimulation. The lines also showed a proliferative response upon stimulation with epithelial kidney cells, purified and cultured from the respective rejected kidneys. These results demonstrate that T cells propagated from rejected human kidney allografts recognize hsp 72. This suggests that hsp-specific T cells may play a role in the rejection process of allograft kidneys.

Cell Line↗
PubMed1996

Morphologically and functionally intact dendritic cells can be derived from the peripheral blood of aged individuals.

Dendritic cells are antigen-presenting cells (APC), which are crucial for the initiation of an immune response. In spite of the well known decline of immune function in old age, no information is yet available on whether dendritic cells are also affected by the ageing process. It was therefore the aim of this study to compare peripheral blood dendritic cells (DC) from old and young healthy individuals. Using granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4, DC were propagated from peripheral blood mononuclear cells (PBMC). The obtained cell populations had a typical dendritic morphology and expressed HLA class I and class II, CD23, CD32, CD40, CD44 and CD54, but not CD3 and CD19. Larger numbers of DC were obtained from old individuals than from young ones in spite of a similar expression pattern of surface molecules. DC from aged persons also survived better under in vitro culture conditions. When tested for their antigen-presenting capacity, DC from young and old individuals were equally effective in inducing the proliferation of tetanus toxoid-specific T cell clones after antigenic stimulation. Peripheral blood DC from aged individuals may thus still function as powerful APC. They may represent useful tools for immunotherapy in the aged.

Adolescent↗
PubMed1996

Retrobulbar fibroblasts from patients with Graves' ophthalmopathy induce downregulation of APO-1 in T lymphocytes and protect T cells from apoptosis during coculture.

Retrobulbar fibroblasts are a main target of the immune process in Graves' ophthalmopathy (GO) and have been shown to have unique metabolic qualities. The aim of our study was to analyze the immunoregulatory properties of retrobulbar fibroblasts and particularly whether fibroblasts were able to protect T cells from apoptosis. Retrobulbar fibroblasts from patients with GO spontaneously expressed higher concentrations of HLA class I and HLA class II (p<0.05) than control cells, whereas basal CD54 expression was unimpaired. Stimulation with IFN gamma led to a more pronounced increase in HLA class I, class II and CD54 in autoimmune fibroblasts than in control cells (p<0.05). Fibroblasts from both groups had the capacity to prevent apoptosis in preactivated peripheral T cells during coculture. T cell survival was, however, more pronounced after coculture with retrobulbar fibroblasts than with control cells (p<0.05). Prevention of T cell death was associated with a decreased expression of APO-1 on the T cell surface, whereas the bcl-2 expression of the T cells remained unchanged. Our results suggest that the increased expression of immunoregulatory molecules combined with a pronounced capacity of autoimmune fibroblasts to protect infiltrating T cells from apoptosis might at least partly explain the site selectivity as well as the perpetuation of the extrathyroidal manifestation of Graves' disease.

Apoptosis↗