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Biomedical subjects

R E Schmidt

Publications and source records attributed to R E Schmidt.

At least 19 recordsLinked to original sources
PubMed1992

Affected paroxysmal nocturnal hemoglobinuria T lymphocytes harbor a common defect in assembly of N-acetyl-D-glucosamine inositol phospholipid corresponding to that in class A Thy-1- murine lymphoma mutants.

Deficient expression of glycoinositol phospholipid (GPI) anchored proteins in affected paroxysmal nocturnal hemoglobinuria (PNH) cells has been traced to a defect in GPI anchor assembly. In a previous study (Schubert, J., Schmidt, R. E., and Medof, M. E. (1993) J. Biol. Chem., in press) we characterized the biosynthesis of putative Man-containing GPI anchor precursors in normal peripheral blood lymphocytes and investigated assembly of these intracellular GPI intermediates in CD48- affected and CD48+ unaffected T and natural killer cell lines of PNH patients. We found that affected T cells from five patients exhibited a uniform defect in which dolichol-phosphoryl-Man was synthesized but no GPI mannolipids were expressed. In this study, membranes of patients' affected T cells were labeled with UDP-[3H]GlcNAc to evaluate earlier steps in GPI synthesis, and intact cells were fused to Thy-1- murine lymphoma mutants harboring different defects in early GPI assembly to test for the presence of corresponding or complementary lesions. In all cases, affected cell membranes failed to assemble GlcNAc-inositol phospholipid, the initial precursor of GPI anchor structures, and the intact cells failed to complement class A mutants while complementing other classes. Affected polymorphonuclear leukocytes from three additional patients of different origin were then labeled with [3H]Man and the labeling patterns found to correspond to those obtained with the T lymphocytes. Taken together the data indicate that the genetic lesion in PNH cells resides in a DNA element which: 1) encodes a product required for the synthesis of GlcNAc-inositol phospholipid, 2) corresponds to that altered in class A Thy-1- murine lymphoma mutants, and 3) is commonly affected in different patients.

Acetylglucosamine↗
PubMed1992

Exogenously-induced, natural killer cell-mediated neuronal killing: a novel pathogenetic mechanism.

Many human neurodegenerative diseases are characterized by the idiopathic death of cells narrowly restricted to a subset of neurons in a specific functional neuroanatomic system. Few in vivo models exist for the analysis of these types of degeneration. This report documents the death of sympathetic neurons resident in the superior cervical ganglia of rats after exposure to an exogenous chemical agent, the drug guanethidine, as being mediated by natural killer (NK) cells. This is the first in vivo model of a disorder of the nervous system in which NK cells appear to be the principal effector cell, and thus could serve a central role in dissecting the normal and pathological function of NK cells. In addition, this pathogenetic mechanism appears to represent a novel type of autoimmune reaction that could have a direct bearing on a number of human illnesses.

Animals↗
PubMed1992

Immunohistochemical characterization of NPY and substance P containing nerve terminals in aged and diabetic human sympathetic ganglia.

To compare the neuropeptide specificity of dystrophic axon formation in aging versus diabetic human sympathetic ganglia we have immunohistochemically characterized neuropeptide Y (NPY) and substance P containing intraganglionic nerve terminals. Prevertebral superior mesenteric but not paravertebral superior cervical ganglia developed markedly swollen NPY containing axonal termini with both aging and diabetes. Substance P containing nerve terminals failed to develop dystrophic changes. Selective loss of classes of nerve terminals may result in discrete functional sequellae.

Aged↗
PubMed1992

CD16- CD56+ natural killer cells after bone marrow transplantation.

Natural killer (NK) cells are phenotypically defined as lymphocytes expressing the antigens CD56 and mostly CD16 (Fc gamma RIII), but lacking CD3. A small CD3- CD16- CD56+ NK cell subset has been described in normal individuals representing less than 2% of peripheral blood lymphocytes. We analyzed here 70 patients for their reconstitution of the immune system during follow-up after autologous or allogeneic bone marrow transplantation. In 35% of these patients, two different NK cell subsets, namely CD56+dim and CD56+bright cells, were observed. The mean duration of these two subsets after transplant was 4 months. Sixty-five percent of the patients exhibited an increased number of NK cells, but only the typical CD16+ CD56+dim population. The CD56+bright subpopulation represented a particular CD3- CD16- NK subset, with posttransplant frequencies up to 70% of all NK cells and 40% of peripheral blood lymphocytes, respectively. In contrast to normal CD56+dim NK cells, CD56+bright cells coexpressed the activation antigens p75 beta-chain of interleukin-2 receptor (IL-2R), CD2R, and CD26, but were negative for CD16. NK and antibody-dependent cellular cytotoxicity activity of CD56+bright cells was low compared with CD56+dim NK cells. But using IL-2 and interferon gamma, their cytotoxicity could be enhanced even more than in CD56+dim lymphocytes. These different subsets may reflect distinct activation or differentiation steps of NK cells during reconstitution of the immune system. Their differential response to IL-2 may be of functional importance for posttransplant cytokine therapy.

Adult↗
PubMed1992

Differences in activation of normal and glycosylphosphatidylinositol-negative lymphocytes derived from patients with paroxysmal nocturnal hemoglobinuria.

In these studies, the role of glycosylphosphatidylinositol (GPI)-anchored surface molecules during T cell activation was investigated in fresh T cells and T cell lines obtained from patients with paroxysmal nocturnal hemoglobinuria. For control, GPI-expressing T cells of the same patients were used. Unstimulated GPI- T cells exhibited significantly reduced surface expression of the activation Ag CD45R0, compared with GPI+ T cells. In addition, in measurements of proliferation, IFN-gamma production, and induction of second messengers such as cytoplasmic Ca2+, CD48- lymphocytes showed a similar response to TCR-specific stimulation, compared with CD48+ lymphocytes. In contrast, stimulation with the lectin PHA produced a decreased response of CD48- lymphocytes in these functions. In addition, stimulation with cross-linked CD59 mAb increased the proliferation of GPI-molecule expressing CD48+ T cell lines only. From these data, it can be concluded that GPI-anchored surface molecules play an important role in T lymphocyte activation.

Antigens, CD↗
PubMed1992

The glycosylphosphatidylinositol-linked Fc gamma receptor III represents the dominant receptor structure for immune complex activation of neutrophils.

Polymorphonuclear neutrophils (PMN) express constitutively two low-affinity Fc gamma receptors, Fc gamma RII and Fc gamma RIII. Fc gamma RII is a transmembrane molecule, and Fc gamma RIII is linked via a glycosylphosphatidylinositol (GPI) anchor to the membrane. The role of each of these receptors in activation of PMN is still unclear. We used specific cross-linking of Fc gamma RII via Fab fragments of IV.3 (anti-Fc gamma RII, CDw32) and of Fc gamma RIII using F(ab')2 fragments of 3G8 (anti-Fc gamma RIII, CD16) to activate PMN. Stimulation of Fc gamma RIII was significantly more effective in inducing a respiratory burst than cross-linking of Fc gamma RII. A synergistic effect was observed after simultaneous activation of Fc gamma RIII. We could demonstrate that both Fc gamma R mobilize calcium as intracellular signal in spite of their different membrane linkage. The kinetic of calcium mobilization after Fc gamma R stimulation is delayed in comparison to formyl-methionyl-leucyl-phenylalanine activation. In addition Fc gamma R-induced increase of cytoplasmic calcium is pertussis toxin insensitive. When monoclonal IgG1 kappa complexes were used for stimulation calcium mobilization and hydrogen peroxide (H2O2) production could also be demonstrated. Inhibition studies of this activation using monoclonal antibodies suggested that this immune complex activation was predominantly mediated via Fc gamma RIII. Only in Fc gamma RIII-deficient PMN from paroxysmal nocturnal hemoglobinuria patients could a decreased H2O2 production be demonstrated to be Fc gamma RII dependent. In normal PMN the GPI-anchored Fc gamma RIII structure is the predominant receptor.

Antigen-Antibody Complex↗
PubMed1992

Fc gamma RIII activation is different in CD16+ cytotoxic T lymphocytes and natural killer cells.

The transmembrane protein CD16 (Fc gamma RIII) is detected on activated macrophages, natural killer (NK) cells and a small subset of T lymphocytes. From CD3-CD56+ CD16+bright NK cells and CD3+ CD56+ CD16+dim non-major histocompatibility complex (MHC)-restricted cytotoxic T lymphocyte (CTL) clones were generated reflecting the stable, but different, CD16 expression of the respective peripheral blood subpopulations. To compare the role of CD16 on NK cells and non-MHC-restricted CTL, Fc gamma RIII activation and its mechanisms were investigated using monoclonal antibodies (mAb). Cross-linking of CD16 induced Ca2+ influx in CD16+bright NK clones. In contrast, there was no Ca2+ mobilization after CD16 activation in CD16+dim CTL, which revealed a good response to cross-linking of CD3 antigen. Pretreatment with CD16 mAb alone or cross-linked CD16 mAb did not block the CD3 response of CD16+dim CTL. Again, CD16 cross-linking induced more interferon-gamma transcription in NK cell clones than in non-MHC-restricted CTL clones. Also a higher tumor necrosis factor-alpha production of NK clones after CD16 cross-linking compared to CD16+dim CTL could be observed. These data suggest that after CD16 activation CD16+dim CTL and CD16+bright NK cells use different second messengers. In addition, signal transduction via CD3 and CD16 appears to function independently in CD16+dim non-MHC-restricted CTL.

Antibodies, Monoclonal↗
PubMed1992

Ti gamma A + delta TCS1+ T cells in human thymus. Analysis of the T cell receptor.

TcR1+ T cells in peripheral blood have been shown to express in an exclusive fashion either the Ti gamma A or the delta TCS1 epitope. Here, we characterize a subset of TcR1+ T cells in fresh thymus co-expressing the Ti gamma A and delta TCS1 epitopes. TcR1dim and TcR1bright clones can be distinguished. Biochemical and molecular studies on both types of clones generated from these thymocytes reveal a unique T cell receptor structure characterized by the use of a V gamma 9/C gamma 2-encoded 55-kDa gamma chain nondisulfide linked to a V delta 1-encoded delta chain.

Cell Line↗
PubMed1992

Fine structure of presynaptic axonal terminals in sympathetic autonomic ganglia of aging and diabetic human subjects.

The neuropathologic changes that may underlie autonomic nervous system dysfunction in nondiabetic elderly human subjects or as a complication of diabetes have been systematically examined in sympathetic ganglia of a series of autopsied human subjects. As in animal models of aging and diabetes, enormously swollen terminal axons were found closely apposed to the perikarya of principal sympathetic neurons in prevertebral superior mesenteric sympathetic ganglia of aged and diabetic human subjects. Dystrophic axons consisted of two stereotyped forms: the first was composed of large numbers of misaligned aggregates of neurofilaments surrounded by variable numbers of small dense core vesicles; the second was characterized by large numbers of mitochondria, vacuoles, and dense and multivesicular bodies. The fine structural characteristics of neuroaxonal dystrophy, its predilection for prevertebral rather than paravertebral sympathetic ganglia, and the tendency for multiple dystrophic axons to cluster preferentially around selected neurons were identical in aged and diabetic human ganglia and were similar to changes seen in animal models of aging and diabetes. Neither diabetic nor aging ganglia demonstrated evidence of neuronal degeneration. Such structural changes may represent a degenerative influence of diabetes and aging on the normal remodeling of nerve terminals in autonomic ganglia, i.e., the continually ongoing process of turnover and replacement of axonal terminals. Similarity of lesions in human diabetes and aging suggests the possibility of pathogenetic mechanisms that are common to diabetes and the aging process. The substantial parallels between humans and animal models provide support for the validity of testing some proposed pathogenetic mechanisms directly in animal models.

Adolescent↗
PubMed1992

Analysis of CD16+dim and CD16+bright lymphocytes--comparison of peripheral and clonal non-MHC-restricted T cells and NK cells.

The Fc gamma RIII receptor (CD16) has been described on natural killer cells and a small subset of T lymphocytes. CD16+bright lymphocytes represent the typical population of peripheral blood CD3- NK cells. In these studies in addition to CD16+bright NK cells Fc gamma RIII expressing cytotoxic T lymphocytes in peripheral blood from one healthy individual are characterized as CD16+dim non-MHC-restricted CTLs either expressing the alpha/beta (80%) or the gamma/delta T cell receptor (20%). Both CD16+ subsets are clearly distinct in their functional capacity performing NK and ADCC activity. Freshly isolated CD16+dim T cells exert higher ADCC, CD16+bright NK cells higher NK activity. They are also differentially activated by interleukin-2 since CD16+bright NK cells reveal a bright expression of the p75 IL-2 receptor beta-chain in contrast to the very low p75 expression on CD16+dim T cells. This activation leads to a gradual increase of ADCC by NK cells. Finally the CD16 expression pattern with low and bright intensity represents a stable phenotype expressed by clones generated from these different subpopulations. On a clonal level CD16+dim non-MHC-restricted T cells can be distinguished from CD16+bright NK cells by their lower capacity in NK killing, but they are equally potent in ADCC. Finally these CD3+CD16+dim clones provide the basis for studies of Fc gamma RIII and TcR interaction.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1992

Enhancement of nasal delivery of a renin inhibitor in the rat using emulsion formulations.

Nasal absorption of O-(N-morpholino-carbonyl-3-L-phenylaspartyl-L-leucinamide of (2S,3R,4S)-2-amino-1-cyclohexyl-3,4-dihydroxy-6-methylheptane (I), a renin inhibitor, was evaluated in two rat nasal models, one involving surgery and the other requiring no surgical intervention. Oleic acid/monoolein emulsion formulations were tested along with a control PEG 400 solution. The percent absolute bioavailability of the compound was enhanced from 3-6% (PEG 400 solution) to 15-27% when the emulsion formulations were used. The different nasal model techniques (with and without surgery) did not produce any statistical difference in the absolute bioavailability values for I. Emulsion formulations did not produce appreciable damage as assessed morphologically. It is suggested that emulsion formulations containing membrane adjuvants such as oleic acid and monoolein can be used to enhanced the nasal delivery of low-bioavailable, lipid-soluble drugs.

Administration, Intranasal↗
PubMed1992

Non-MHC-restricted T-cell interaction with B cells: role of the T-cell receptor.

Non-specific antibody production usually accompanies the T-cell-regulated B-cell response. In this paper the mechanisms involved in non-MHC-restricted T-B-cell interaction were studied. As previously shown for NK cells, activated B cells induce IFN-gamma and TNF alpha production in non-MHC-restricted cytotoxic T lymphocytes (NrCTL). Using an in vitro model system, we demonstrate that direct cell-cell interactions are required to induce these cytokines in NrCTL. Receptor ligand systems involved are leucocyte function antigen-1/intercellular adhesion molecule-1 (LFA-1/ICAM-1)(CD11a, CD18/CD54), T11/LFA-3 (CD2/CD58), and the clonotypic T-cell receptor (TCR) structure NKTa of JT9/JT10 with its non-MHC-related target antigen TNKtar (4F2). Cytokine production can be induced by activating monoclonal antibodies against CD2R. Antibodies against the clonotypic TCR (NKTa) or CD3 had no cytokine-inducing effect on NrCTL cultured alone, but were able to retrieve the effect of blocking the target antigen on co-cultured B cells. We could further demonstrate that the inhibition of the TCR/target antigen interaction could be overcome by close cell-cell contact culture conditions. From these findings it is concluded that the role of the TCR in non-MHC-restricted cell-cell interaction is to facilitate LFA-1/ICAM-1-mediated effector target adhesion in a specific way rather than to mediate direct activating signals upon lymphokine production or cytotoxicity.

B-Lymphocytes↗
PubMed1992

[Shedding of soluble intercellular adhesion molecule 1 (ICAM-1) from melanoma cells and the effect on cellular cytotoxicity].

ICAM-1-mediated cell-cell adhesion is essential for various immunologic functions, including non-MHC-restricted cytotoxicity. Shedding of ICAM-1 occurred after stimulation of melanoma cells with TNF alpha and IFN gamma. Soluble forms of ICAM-1 inhibited the conjugate formation of NK clones with K562 and of LAK cells with melanoma cells. Furthermore, the non-MHC-restricted cytotoxicity mediated by NK clones or LAK cells could be abrogated by soluble ICAM-1.

Cell Adhesion↗
PubMed1992

[Fc gamma receptors: structure, function, and clinical significance].

Fc gamma receptors are a group of three different receptors with several subtypes. They are widely distributed on many cells of the immune system and contribute to the pathogenesis of immune complex- and autoantibody-mediated diseases such as vasculitis, rheumatoid arthritis, idiopathic thrombocytopenic purpura or autoimmune neutropenia. This review focuses on the structure, distribution and function in Fc gamma receptors and their subtypes.

Antigen-Antibody Complex↗
PubMed1992

[The GPI-anchored Fc gamma receptor III in the activation of granulocytes].

PMN express primary two Fc gamma receptors for IgG immune complexes. Fc gamma RII is a transmembraneous molecule in contrast to Fc gamma RIII on PMN which is GPI-linked. In spite of the different membrane linkage both Fc gamma R use calcium as an intracellular signal. Cross-linking of Fc gamma RIII is more effective for induction of H2O2 production than Fc gamma RII. Monoclonal IgG1x cryoglobulin complexes activate PMN via Fc gamma RIII as shown by calcium mobilization and H2O2 production.

Antigens, Differentiation↗