[Presentation of a mixed local area network with Apple Macintosh computers, MS-Dos compatible PC's and/or a Sun workstation].
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Computer Systems↗
Biomedical subjects
L A Huber
Publications and source records attributed to L A Huber.
[The immunology of aging: immunoregulatory role of lipoproteins].
This report deals with immunoregulation by lipoproteins and with age-related changes in immune function. It was investigated whether a diminished immune response during ageing could be caused by a disturbed interaction of lipoproteins with cells of the immune system. The aim of these investigations was to show whether changes in the immune response in the elderly were really age-related, or attributable to other factors (i.e. medication, life style) not related to ageing per se. Therefore, admission criteria for blood donors to take part in these studies of the ageing human immune system were set up by using the Senieur protocol (EURAGE). An immunoregulatory influence of lipoproteins from different density fractions-Low Density Lipoproteins (LDL), High Density Lipoproteins (HDL) and Very Low Density Lipoproteins (VLDL) on the in vitro mitogen response of human peripheral blood lymphocytes (PBL) was shown. Lymphocytes can take up lipoproteins by receptor-mediated (specific binding) and non receptor-mediated (receptor-independent exchange) mechanisms. In this context a HDL-binding site/receptor was demonstrated and characterised here for the first time on human T-cells. Furthermore, interactions of lipoproteins with lymphocytes were investigated in the elderly and compared with young control groups. The increased LDL uptake during ageing was found to correlate with an increased HDL uptake. The age-related diminished immune response correlated with a decrease in plasma membrane fluidity of human PBL, but not with an enhanced lipoprotein uptake. The Senieur protocol in this present form, used for classifying blood donors, had no influence on distribution and statistical processing of the obtained sets of data, indicating that this protocol needs further modifications.
Adult↗
Promotion of lymphocyte growth by high density lipoproteins (HDL). Physiological significance of the HDL binding site.
The characteristics and physiological relevance of the high density lipoprotein (HDL) binding site on unstimulated and mitogen activated human peripheral blood lymphocytes have been investigated. At 37 degrees C, specific binding/uptake of fluorescent (dioctadecylin-docarbocyanine, DiI) HDL was observed by cells from healthy donors as well as by those from low density lipoprotein receptor-defective patients; mitogen activated T-blasts exhibited a markedly elevated DiI-HDL uptake compared to resting T-cells. Binding was saturable at 37 degrees C and of high affinity, with a Kd of 5 x 10(-8) M. It was blocked by anti-apoAI polyclonal antibodies (F(ab)2 fraction), but not by anti-apolipoprotein (apo)E, anti-apoAII, or anti-apoB, and was inhibited competitively by HDL apoproteins and an apoAI-protein A fusion protein. T-cell associated DiI-HDL was increased by trypsin treatment (of the cells) and decreased by activation in the presence of HDL or low density lipoprotein. Comparison of the concentration dependencies of growth promotion and specific cell association of HDL indicated that two mechanisms of lipid exchange may be in operation: one a binding-dependent mechanism of cholesterol exchange, with maximal effect in the HDL concentration range (20-200 micrograms/ml) in which specific binding increases rapidly, and the other a binding-independent exchange of lipids effective at concentrations in which specific binding is saturated (300-5000 micrograms/ml).
Adult↗
Use of a FACS III for fluorescence depolarization with DPH.
We have previously demonstrated age-related differences in human lymphocyte membrane fluidity, by use of steady-state polarization measurements on bulk cell suspensions with the fluorescence probe DPH. However, for exact analysis of the possible functional importance of these changes, single-cell measurements were deemed of interest. We have now used an analog division device to measure fluorescence depolarization "p" of DPH in real time with a FACS III flow cytometer. The measurements are reliable, as we have been able to confirm the differences in DPH "p" between monocytes and lymphocytes previously shown in bulk suspension and to demonstrate the expected differences in fluidity of lipid-modulated cells. We also found significant differences in DPH "p" between lymphocytes of young and elderly blood donors. Lymphocyte subsets did not differ in polarization values but did differ in fluorescence intensity with Th less than Ts less than B = NK cells.
Adult↗
Immunodeficiency in old age.
Aging is a multi-facetted process, but the deterioration of the immune function seems to play a central role in this context. Paradoxically, immune reactivity against exogenous antigens declines during aging while autoimmune reactivity increases. One of the aims of our investigations on the function of the senescent immune system was to define immune parameters of 'normal' aging, i.e. those not dependent on underlying diseases. Specifically, our interest was focused on the possible role of an altered lipid metabolism of cells of the immune system during aging. The known decrease of plasma membrane fluidity of lymphoid cells and monocytes in higher age may be one of the factors responsible for the nonoptimal functioning of the immune system. This property, in turn, seems to be based on an altered lipid metabolism. Specifically, we have evidence that the finely tuned balance between the transport of cholesterol to and from lymphoid cells via the environment and the intracellular cholesterol biosynthesis seems to be disturbed with increasing age. This conclusion is drawn from experiments where low-density lipoprotein (LDL) and high-density lipoprotein (HDL) receptor activity is assessed using fluorescently labeled lipoproteins in fluorescence-activated cell sorter (FACS) analyses. LDL receptor uptake is unexpectedly increased in the elderly, but LDL receptor regulation, and serum LDL composition itself seem to be normal. Preliminary data point out the possibility that the efflux of cholesterol via HDL may be insufficient. Attempts to modulate plasma membrane fluidity by means of the phospholipid mixture 'active lipid 721' (AL 721) showed that this drug, in contrast to literature reports, is not a 'membrane fluidizer' but rather exerts this effect as a nutrient for lymphocytes and monocytes.
Aging↗
Approach to define "normal aging" in man. Immune function, serum lipids, lipoproteins and neopterin levels.
In 53 healthy women with mean age 25.1 years (age range 21-34 years) and in 51 healthy women with mean age 82.1 years (age range 75-91 years), a panel of immunological and biochemical tests was performed. These tests, comprising lymphocyte mitogen responsiveness, phenotyping of lymphocytes, uptake of low density lipoprotein by T cells, serum levels of neopterin, lipids and lipoproteins, as well as routine blood chemistry, were investigated for a possible effect of age and of the classification according to the SENIEUR Protocol of admission criteria by the European Economic Community's Concerted Action Program on Aging (EURAGE). A highly significant effect of age on serum levels of neopterin, lipids and lipoproteins was found. No clear effects, however, of SENIEUR status on these variables was detected. As expected, age had a significant impact on mitogen responsiveness of T cells. Proportional numbers of helper/inducer and cytotoxic/suppressor T cells (as well as antigen density on these cells) were not influenced by age. SENIEUR classification did not affect these immunologic variables. Thus, most of the tested variables that are not included in the SENIEUR admission criteria appear to present information not yet covered by the SENIEUR variables. Various ways for a possible revision or extension of the SENIEUR Protocol are discussed.
Adult↗
Two-dimensional gel mapping of small GTPases reveals transformation-specific changes during oncogenesis.
Epithelial cells transformed by oncogenes in vitro change their gene expression program, thereby losing features of cell polarity and cell adhesion. Using ras-transformed mammary epithelial cells, we have investigated the expression of other small GTP-binding proteins by high-resolution two-dimensional gel electrophoresis and direct GTP ligand binding after renaturing transfer onto nitrocellulose. Ras-transformed cells lost the expression of one epithelial-specific GTP-binding protein (21-22 kDa, pI 4.5-4.8) and instead expressed a fibroblast GTP-binding protein (21-22 kDa, pI 4.8-5.0).
Animals↗