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At least 181 records · Page 10Linked to original sources
PubMed1992

Human postnatal thymocytes generate phenotypically immature CD3dim, CD5dim, CD1abright progeny in organ culture.

We previously described an organ culture system that supports the in vitro development of human fetal thymocytes in murine alymphoid thymic rudiments without addition of exogenous factors. This approach to study human T cell precursors is limited by the requirement for fetal tissue. We show that human thymocytes from pediatric sources can be expanded under similar conditions. Organ cultures generated predominantly CD4 CD8 double positive cells, most of which maintained the phenotype CD3dim, CD5dim, and CD1abright, characteristic for double positive thymocytes ex vivo. This culture system should facilitate in vitro studies on human thymocyte development and repertoire selection.

Animals↗
PubMed1989

HIV-1-specific B cell activation. A major constituent of spontaneous B cell activation during HIV-1 infection.

B cell activation is a well known consequence of HIV-1 infection, and seropositive subjects show high numbers of spontaneously activated Ig-secreting cells in circulation. To better define the importance of the HIV-1-specific response in this phenomenon, we first studied whether in vitro spontaneous anti-HIV-1 antibody production was accompanied by reactivation of memory B lymphocytes. Unstimulated PBL from HIV-1-infected individuals with prior history of hepatitis B and/or EBV infection did not consistently show spontaneous in vitro synthesis of anti-hepatitis B core Ag or anti-EBV antibodies; in addition, PWM-induced synthesis of anti-hepatitis B virus and anti-EBV antibodies was decreased compared to HIV-1-seronegative subjects. Moreover, in comparing the frequencies of activated HIV-1-specific B cell precursors and activated Ig-secreting precursors in limiting dilution experiments, a sizable fraction (20 to 40%) of circulating cells spontaneously secreting Ig produced antibody against HIV-1 determinants. The ratio between the two frequencies fitted in very well with the amount of Ig removed from unstimulated culture supernatants after HIV-1-specific antibody absorption with solid-phase HIV-1. These findings indicate that B cell activation during HIV-1 infection is mainly oriented toward a specific response to HIV-1 determinants; the possible relevance of this phenomenon to lymphomagenesis in AIDS patients is discussed.

Absorption↗
PubMed1979

Role of self carriers in the immune response and tolerance. IV. Active T cell suppression in the maintenance of B cell tolerance to a "T-independent" antigen.

Previous studies indicated that T cells are required for tolerance induction by hapten-modified syngeneic spleen cells (TNP-SC) in vivo. The role of T cells in the maintenance of this unresponsive state has been examined herein. By three criteria--limiting dilution precursor analysis, removal of T cells by anti-Thy-1 + C, and direct mixing experiments--we show that T cells are required for the continued suppression of the B cell response to the T-independent antigen, TNP-POL. Suppressor cells can also be induced by TNP-teratoma cells, which lack detectable H-2 antigens. Both anti-Ly-1 + C and anti-Ly-2 + C treatment reversed suppression induced by TNP-SC. These results demonstrate that normal B cell reactivity is present in the spleens of mice rendered tolerant by haptenated self, but that Ly-1,2,3 or Ly-1 + Ly-2,3 suppressor T cells prevent their responsiveness.

Animals↗
PubMed1988

[Treatment of AL amyloidosis without myeloma].

AL amyloidosis is a serious complication of monoclonal gammopathy. The therapeutic strategy in amyloidosis associated with myeloma is to decrease the amyloidogenic precursor synthetised by the monoclonal plasmocytic proliferation. However, when systemic amyloidosis complicates a so called "benign" monoclonal gammopathy, this therapeutic approach is debatable. We report 10 cases of AL amyloidosis without myeloma treated by chemotherapy. Eight patients were initially given alkylating agents (cyclophosphamide or melphalan) which had no effect on the clinical progression of their systemic amyloidosis or on the plasma concentrations of the precursor. A limited open clinical trial including 4 patients was then undertaken based on the Vincristine, Adriamycine, Dexamethasone combination recently proposed for cases of resistant myeloma. A 50% reduction in the serum monoclonal protein was observed in 2 patients with this treatment. However, the mean survival of the 10 patients (25 months) was not longer than that previously reported for patients receiving more conventional treatment. The results of this limited trial indicate the need for further controlled therapeutic trials with larger numbers of patients in order to assess the effect of polychemotherapy in patients with AL amyloidosis.

Adult↗
PubMed1982

Effect of recent antigen exposure on the functional expression of B cell subpopulations.

We investigated whether the definition of functional B cell subpopulations changes after the exposure of B cells to specific antigen. Recent in vivo priming with fluorescein- (FL) coupled T-independent (TI) antigens leads to an augmentation of the subsequent in vitro responses of B cells to FL-coupled TI antigens, including FL-polymerized flagellin, FL-lipopolysaccharide, and FL-Brucella abortus, as well as a FL-coupled T-dependent (TD) antigen, FL-keyhole limpet hemocyanin (KLH). This effect, which is evident 7 days after priming, is of short duration in that B cells from FL-Ficoll injected mice display normal responsiveness 3 wk after priming. When mice are primed with FL-KLH, the TD antigen, B cells responsive to a subsequent FL-KLH challenge are expanded, but not short-term cross-priming for any of the TI antigen challenges is observed. Limiting dilution precursor analysis shows that B cell populations responding to different FL-coupled TD and TI antigens overlap in unimmunized animals. FL-TI antigen priming induces not only quantitative changes in the responding B cells (increased precursor frequencies) but also results in functional changes in FL-specific B cells. The primed B cells now respond to FL-hapten in a carrier-restricted manner and behave as independent (non-overlapping) subpopulations. We suggest that B cell responses to different forms of the same hapten are influenced in part by their recent "history" of antigenic exposure.

Animals↗
PubMed1994

Relationship of HIV-1 provirus load, CD8+ CD11+ T cells and HIV-1 envelope-specific cytotoxic T lymphocytes in HIV-infected asymptomatic offients.

The course of human immunodeficiency virus (HIV) infection progresses from an acute infection, through a prolonged asymptomatic phase, to an immunocompromised state. Some of the possible mechanisms underlying immune dysfunction include decreased HIV-specific cytotoxic T lymphocyte (CTL) activity, increased suppressor T cells, and/or increased HIV load. However, no study has been carried out to correlate all these factors. In this study, 26 patients showed > 3 log DNA copy number/10(6) CD4+ T cells, and seven patients had < 3 log DNA copy/10(6) CD4+ T cells. Patients with higher virus load had greater than 15% (19-45%) CD8+ CD11+ T cells. HIV-1 envelope-specific, HLA-restricted CTL activity (> 10%) was observed in 11 of 25 asymptomatic patients, and the remaining 14 patients lacked CTL activity (< 10%) in bulk assay. Although CTL activity was undetectable in these individuals, there was no significant difference in the frequency of activated CTL and their precursors in limiting dilution analysis. The patients with undetectable CTL activity had a higher percentage of CD8+ CD11+ T cells and a higher HIV-1 DNA copy number/million CD4+ T cells. Each of these parameters were significantly correlated with CD4+ T-cell numbers. The inverse relationship of CD8+ CD11+ T cells and virus load with HIV-specific CTL activity observed in this study may be one of the underlying factors which determines the course of HIV infection.

CD11 Antigens↗
PubMed1983

Limiting dilution analysis of alloreactive cytotoxic precursor cells in aging mice.

The quantitative minimal estimate of the frequency of alloantigen specific cytotoxic T lymphocyte precursor cells (CTL-p) was determined in young and old C57BL/6 mice by limiting dilution analysis. Supernatant from phorbol myristate acetate-induced EL-4 cells was used as a source of IL 2 in these assays, which therefore were independent of the presence of the Lyt-2-, IL 2-producing cells known to be deficient in aging mice. These studies showed that 24-mo-old mice had approximately 10-fold fewer CTL-p than their young counterparts. Comparison of the limiting dilution assay (LDA) with IL 2-supplemented primary MLC shows that estimates of the frequency of CTL-p do not consistently agree with cytotoxic activity detected in the higher cell density primary MLC, and that the LDA is most likely a better estimate of the effect of age on the development of CTL.

Aging↗
PubMed2006

Templated deposition of MoS2 nanotubules using single source precursor and studies of their optical limiting properties.

We demonstrate a simple way of fabricating bulk quantities of molybdenum disulfide (MoS2) porous nanotubules (NTs) by templated deposition from a single source precursor based on tetrakis(diethylaminodithiocarbomato)molybdate(IV). Bulk quantities of crystalline MoS2 NTs that consist of agglomerates of nested nanocapsules were obtained by this one-step evaporation method. We found that MoS2 NTs show good optical limiting behavior with 532-and 1064-nm nanosecond laser pulses, and the size-effect of the NTs on optical transmission was observed.

Journal Article↗
PubMed2003

Chronic fatigue syndrome: new evidence for a central fatigue disorder.

Considerable evidence points towards a prominent role for central nervous system (CNS) mechanisms in the pathogenesis of chronic fatigue syndrome (CFS), a disorder characterized chiefly by persistent, often debilitating, fatigue. We wished to characterize circulating profiles of putative amino acid modulators of CNS 5-hydroxytryptamine (5-HT; serotoninergic) and dopaminergic function in CFS patients at rest, as well as during symptom-limited exercise and subsequent recovery. Groups of 12 CFS patients and 11 age- and sex-matched sedentary controls, with similar physical activity histories, underwent ramp-incremental exercise to the limit of tolerance. Plasma amino acid concentrations, oxygen uptake and ratings of perceived exertion were measured at rest, and during exercise and recovery. Peak oxygen uptake was significantly lower in the CFS patients compared with controls. Rating of perceived exertion in the patients was higher at all time points measured, including at rest, relative to controls. Levels of free tryptophan (free Trp), the rate-limiting 5-HT precursor, were significantly higher in CFS patients at exhaustion and during recovery, whereas concentrations of branched-chain amino acids (BCAA) and large neutral amino acids (LNAA) were lower in CFS patients at exhaustion, and for LNAA also during recovery. Consequently, the [free Trp]/[BCAA] and [free Trp]/[LNAA] ratios were significantly higher in CFS patients, except at rest. On the other hand, levels of tyrosine, the rate-limiting dopaminergic precursor, were significantly lower at all time points in the CFS patients. The significant differences observed in a number of key putative CNS 5-HT and dopaminergic modulators, coupled with the exacerbated perception of effort, provide further evidence for a potentially significant role for CNS mechanisms in the pathogenesis of CFS.

Adult↗
PubMed1997

Limiting dilution analysis of primary cytotoxic T-cell precursors.

An efficient colorimetric assay has been adapted for limiting dilution analysis of cytotoxic T-cell precursors. Application of this assay in a suitable experimental model of thymic education could be especially useful in identifying factors that shape the CD8 T-cell repertoire. The essential elements of such a model are described here and elsewhere.

Animals↗
PubMed1983

Onset of neurophysin self-association upon neurophysin/neuropeptide hormone precursor biosynthesis.

The potential of the common biosynthetic precursor of neurophysin and neuropeptide hormones to self-associate has been assessed by quantitative affinity chromatographic analysis. The precursor form, with the hormone sequence in the amino terminal region and assumed able to interact intramolecularly with the hormone binding site of the neurophysin domain of the folded precursor, exhibits an affinity for neurophysin-agarose which is intermediate between those of unliganded neurophysin and non-covalently hormone-liganded neurophysin. The results lead to a prediction that neurophysin self-association is established upon precursor synthesis and prior to limited proteolysis of the precursor to release mature neurophysin and hormone components. Such self-association could play a role in packaging of the precursor into secretory granules and in regulating subsequent precursor processing events within the granules.

Animals↗
PubMed2003

Novel precursor substrates for polythioesters (PTE) and limits of PTE biosynthesis in Ralstonia eutropha.

A novel class of biopolymers referred to as polythioesters (PTE) was recently detected when the polyhydroxyalkanoate (PHA) accumulating bacterium Ralstonia eutropha was cultivated in the presence of 3-mercaptopropionic acid (3MP) or 3,3'-thiodipropionic acid (TDP). In this study, 3,3'-dithiodipropionic acid (DTDP) and 3-mercaptovaleric acid (3MV) were identified as two additional precursor carbon sources for in vivo biosynthesis of PTE in R. eutropha. Biosynthesis of copolymers of 3-hydroxybutyrate (3HB) and 3MP, which contributed 19-25% of cell dry matter, was compared referring to the different precursor substrates. Using DTDP as carbon source, which is probably cleaved into two molecules 3MP, yielded an about 2.3-fold higher molar 3MP content of the copolyester than TDP, which is probably cleaved into only one molecule 3MP. Furthermore, cultivation of R. eutropha in the presence of 3MV resulted in biosynthesis of copolymers consisting predominantly of 3HB with low amounts of 3MV and 3-hydroxyvalerate, each contributing less than 5 mol% of the constituents. In contrast, 4-mercaptobutyric acid could be not incorporated into PHAs, although - as documented in this study - five different strategies, various precursor substrates, R. eutropha and also a recombinant strain of Escherichia coli were employed. Therefore, this study not only extended the range of substrates suitable for PTE biosynthesis and also the range of PTE constituents in R. eutropha, it also demonstrates limits for PTE biosynthesis in this bacterium.

3-Mercaptopropionic Acid↗
PubMed1986

Limit dilution analysis of mast cell precursor frequency in the gut epithelium of normal and Trichinella spiralis infected mice.

Previous studies have established that the gut nematode Trichinella spiralis induces a dramatic thymus dependent intestinal mastocytosis which peaks within 6 to 12 days after primary oral infection. It is not known, however, if the increase in gut mast cells results from the influx of mast cells or their precursors, or from the expansion and differentiation of mast cell precursors (MCP) that are normally present in the small intestinal epithelium. In the present study, the number of mucosal MCP in the intraepithelial lymphocyte (IEL) population and in bone marrow (BM) cells from normal and 4 day T. spiralis infected mice was compared by culturing the cells at limiting dilutions in medium containing interleukin-3 (IL-3). While the MCP frequency in IEL from infected mice was found to be significantly increased in comparison with that found in normal mice, the numbers of MCP in BM from the two groups were equivalent. Resident intraepithelial mucosal MCP therefore undergo a local expansion before the occurrence of an overt T dependent intestinal mastocytosis. This finding lends support to the view that local mucosal T cells are involved in regulating mast cell numbers in response to intestinal helminth infection.

Animals↗
PubMed1996

A cell-saving non-radioactive limiting dilution analysis-assay for the combined determination of helper and cytotoxic T lymphocyte precursor frequencies.

We have developed a limiting dilution analysis-assay which makes the determination of both helper and cytotoxic T lymphocyte precursor frequencies possible. The way in which T helper precursor frequencies are determined in this combined assay is essentially the same as the method published previously. Experimental conditions for the combined assay have been optimized to obtain cytotoxic T lymphocyte precursor frequencies that are comparable to those determined in the assay routinely used in our laboratory. For all situations where the amount of available cell material is a limiting factor, it will be an advantage that with the same number of cells needed for a standard cytotoxic T lymphocyte precursor frequency determination, in the combined assay both helper and cytotoxic T lymphocyte precursor frequencies can be determined. This is especially convenient in the case of bone marrow transplantation, where evidence is accumulating that low or negative cytotoxic T lymphocyte and/or T helper precursor frequencies may be a prerequisite for a successful transplantation with a minimal risk of graft-versus-host disease.

Hematopoietic Stem Cells↗
PubMed1991

Limiting dilution analysis of cytotoxic T lymphocytes to human immunodeficiency virus gag antigens in infected persons: in vitro quantitation of effector cell populations with p17 and p24 specificities.

The presence of cytotoxic T lymphocytes (CTL) to the gag antigens of human immunodeficiency virus (HIV) has been described in infected populations. We found that the majority of this immune response as measured in bulk CTL assays of unstimulated peripheral blood mononuclear cells (PBMC) is directed against the p24 component of the p55 gag precursor protein. Using limiting dilution analysis of this effector cell population we confirm that the majority of activated gag-specific CTL circulating in the PBMC of infected hemophilic patients are directed at p24 determinants and are present at frequencies of 1/36,000 to 1/86,000 lymphocytes. By performing in vitro stimulation after limiting dilution, the precursor population of gag-specific CTL are characterized and quantitated. HIV gag-specific CTL precursors are identified at frequencies of 1/1700 to 1/17,000 lymphocytes and are made up of cells with both p17 and p24 specificities. No HIV gag-specific CTL precursor cells are identified in the PBMC of HIV-uninfected individuals. These studies demonstrate that CTL directed at both p17 and p24 determinants make up the cellular immune repertoire in HIV-infected individuals but that only the p24-specific CTL are routinely found in an activated state in the circulation.

CD8 Antigens↗
PubMed1999

A limited antibody panel can distinguish B-precursor acute lymphoblastic leukemia from normal B precursors with four color flow cytometry: implications for residual disease detection.

Multiparameter flow cytometry may be used to detect minimal residual disease in acute leukemia because leukemic cells often display aberrant phenotypes when compared to normal cells. One limitation of this approach in B-precursor ALL is that leukemic phenotypes are often qualitatively similar to normal marrow B progenitors, though it has long been recognized that the latter show a predictable pattern of antigen expression with differentiation. In this study we used four-color flow cytometry to define precisely the patterns of normal antigen expression on a series of normal bone marrows using two different four-color combinations of antibodies: CD19-APC/CD45-perCP/CD20-PE/CD10-FITC; and CD19-APC/CD45-perCP/CD9-PE/CD34-FITC. A series of dual parameter displays were created in which normal B precursors occupied predictable regions. We then tested these antibody combinations on a series of 82 cases of B-precursor ALL and found that in 76/82 cases (93%) the first combination demonstrated an abnormal population on at least one of the dual parameter displays, and that 72/77 cases tested (94%) showed an abnormality with the second combination. When taken together, 81/82 cases (99%) showed an abnormality. When purified blasts were serially diluted into normal marrows we found a sensitivity of detection of 1 cell in 10(4) normal marrow cells provided sufficient CD19+ cells were acquired to visualize the abnormal population as a discrete cluster. Because the pattern of antigen expression in normals is very reproducible, it is possible to create a fixed set of geometrical regions to define the normal; this makes analysis of an unknown sample very straightforward. We conclude that our approach could be employed as a simple method for the detection of minimal residual disease in B-precursor ALL, and unlike many other methods should prove applicable to virtually all cases of this malignancy.

Antibodies, Monoclonal↗