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PubMed1991

Induction of Fc epsilon RII/CD23 on phytohemagglutinin-activated human peripheral blood T lymphocytes. I. Enhancement by IL-2 and IL-4.

Despite evidence for the expression of low affinity Fc receptor for IgE (Fc epsilon RII)/CD23 in T cell lines and pathologic T cells, Fc epsilon RII/CD23 in normal human T cells is still unclear. We studied the expression of Fc epsilon RII/CD23 on T cells in short-term culture of normal human PBMC stimulated with 15 micrograms/ml PHA. PHA stimulation also resulted in the release of soluble Fc epsilon RII/CD23 (IgE binding factor). Using two-dimensional flow cytometry, more than 10% of the Fc epsilon RII/CD23+ cells were found to co-express CD3 Ag. Both CD4+ and CD8+ T cells expressed Fc epsilon RII/CD23. The induction of Fc epsilon RII/CD23 on PHA-activated T cells was enhanced by IL-2 as well as IL-4. Both IL-2 and IL-4 also augmented PHA-induced production of soluble Fc epsilon RII/CD23. The enhanced expression of Fc epsilon RII/CD23 on T cells by both lymphokines was suppressed by rabbit anti-IL-4 antiserum, suggesting the involvement of an IL-4-dependent process even in the IL-2-dependent Fc epsilon RII/CD23 expression on T cells. The expression of mRNA for Fc epsilon RII/CD23 on PHA and IL-4-stimulated PBMC was examined by Northern blot analysis. Fc epsilon RII/CD23 mRNA was detected in RNA prepared from the T cell fraction depleted of B cells and macrophages (Fc epsilon RII+CD3+ = 6.2%, Fc epsilon RII+CD3- = 0.8%). The expression of the mRNA for Fc epsilon RII/CD23 on CD3+ T cells was also confirmed by in situ hybridization with Fc epsilon RII/CD23 cDNA combined with CD3 rosette formation at the single cell level.

Antibodies, Monoclonal↗

PubMed1991

Isolation and molecular characterization of PosF21, an Arabidopsis thaliana gene which shows characteristics of a b-Zip class transcription factor.

We have isolated a putative transcription factor gene, PosF21, from Arabidopsis thaliana using an indirect cross-hybridization approach. cDNA clones were isolated which encode single repeating amino acids. Such sequences may function as activation domains in transcription factors and may be indicative for such proteins. The clone PosF21 encodes a region very rich in glutamines. Besides this putative activation domain it encodes a protein sequence which shows all the characteristics of a basic-domain/leucine zipper type of DNA-binding domain. PosF21 is expressed constitutively at a low level in young seedlings and in roots, stems and leaves of mature Arabidopsis plants. A genomic clone of PosF21 was isolated and the gene structure was analyzed. Related sequences in Arabidopsis and a wide range of other plants were detected using the putative DNA-binding domain as a probe in cross-hybridization experiments. Transient transformations in tobacco protoplasts were performed using the beta-glucuronidase (GUS) gene as reporter gene. Approximately 400 bp of the 5' genomic region of PosF21 promote expression of the GUS gene in tobacco protoplasts. Evidence for a regulatory function of PosF21 was obtained since co-expression of the full PosF21 protein or its DNA-binding region alone specifically stimulated GUS gene expression directed from the PosF21 promoter by 6-8-fold.

Amino Acid Sequence↗

PubMed1991

mos-induced inhibition of glucocorticoid receptor function is mediated by Fos.

Activation of glucocorticoid hormone-dependent transcription involves the binding of the glucocorticoid hormone to its receptor followed by a specific interaction of the hormone/receptor complex with glucocorticoid responsive elements in the promoter region of hormone-inducible genes. In stably transfected NIH3T3 cells expressing the oncogene product of v-mos or fos, the expression from two glucocorticoid responsive promoters, MMTV LTR and metallothionein IIA (MtIIA), was shown to be impaired and was only transient. Cadmium-dependent MtIIA gene expression was not affected by the expression of v-mos in the cells. In transiently transfected NIH3T3 cells constitutive fos expression also inhibited glucocorticoid hormone-induced expression from the MMTV LTR. However, co-expression of antisense fos (here referred to as sof) inhibited the down-regulatory effect of Fos on glucocorticoid induced gene expression. v-mos expression in NIH3T3 cells induces fos mRNA and functional fos product (Fos) as reflected by its ability to induce expression of a transiently transfected AP-1 dependent reporter plasmid. We show that sof expression inhibits the down-regulatory effect of mos on expression of a transiently transfected pMMTV LTR-CAT. Our findings, thus, strongly suggest that the inhibition of glucocorticoid receptor function in cells expressing the v-mos oncogene is mediated by Fos.

Animals↗

PubMed1991

Novel 150- and 180-kDa glycoproteins that bind transforming growth factor (TGF)-beta 1 but not TGF-beta 2 are present in several cell lines.

We identified transforming growth factor-beta (TGF-beta)-binding proteins which are distinct from previously described TGF-beta receptors or TGF-beta-binding proteins. These TGF-beta-binding proteins migrate as 150- and 180-kDa 125I-TGF-beta 1 affinity-labeled complexes which are consistently co-expressed in A549, Mv1Lu, MG-63, and BS-C-1 cells. They differ from the types I, II, and III TGF-beta receptors in their electrophoretic mobilities, their lack of binding to TGF-beta 2, and their failure to undergo the marked down-regulation seen with types I, II, and III receptors following a 16-h incubation with TGF-beta 1. The 150- and 180-kDa TGF-beta-binding proteins also are distinct from the recently described disulfide-linked TGF-beta 1-binding proteins which are present in rat glomeruli. In contrast to the glomerular TGF-beta 1-binding proteins, the electrophoretic mobilities of the 150- and 180-kDa binding proteins are unchanged following reduction. In addition, the 150- and 180-kDa TGF-beta-binding proteins are present in the detergent-rich phase during Triton X-114 phase separation, whereas the glomerular TGF-beta-binding proteins partition exclusively into the detergent-poor phase.

Affinity Labels↗

PubMed1991

Characterization of an adult muscle acetylcholine receptor subunit by expression in fibroblasts.

To study the functional and structural roles of the epsilon subunit in adult muscle acetylcholine receptor (AChR), we have co-expressed the alpha and epsilon subunits of the mouse receptor in transfected fibroblasts. Ligand binding studies suggest that association of epsilon with alpha subunit results in a lower association rate constant for 125I-labeled alpha-bungarotoxin binding than that of the unassembled alpha subunit, approaching that for toxin binding to the AChR. Furthermore, alpha epsilon complexes contain high affinity binding sites for competitive antagonists and agonists not present in the unassembled alpha subunit, but similar to one of the two nonequivalent binding sites in the adult AChR. Structural analysis of alpha epsilon complexes by sucrose gradient velocity centrifugation suggests that some of the complexes formed are trimers or tetramers of alpha and epsilon subunits. Comparison of these data with those previously obtained for alpha gamma complexes suggests that gamma and epsilon have homologous functional roles and identical structural positions in the fetal and adult AChRs, respectively.

Acetylcholine↗

PubMed1991

Construction of reshaped human antibodies with HIV-neutralizing activity.

Mouse monoclonal antibody (mAb) 0.5 beta binds to the envelope protein gp120 of human immunodeficiency virus (HIV) and neutralizes infection by HIV in vitro. Mouse mAb 0.5 beta, therefore, has potential as a therapeutic agent for the prevention and treatment of acquired immunodeficiency syndrome (AIDS). Since mouse mAbs are highly immunogenic in humans, efforts are being made to humanize mouse mAbs that are being considered for use in humans. This report describes the design, construction, and expression of reshaped human 0.5 beta antibodies. In these antibodies, the entire constant (C) regions were derived from human sequences. The variable (V) regions were derived from human framework regions (FRs) and mouse 0.5 beta complementarity determining regions (CDRs). One version of reshaped human 0.5 beta light (L) chain and six versions of reshaped human 0.5 beta heavy (H) chain were made and tested. Following transient expression in cos cells, all of the constructions were capable of producing humanlike antibody. Three of the H chain constructions (RHc, RHe, and RHf), when co-expressed with the L chain construction (RL), produced reshaped human antibody capable of binding to the epitope on gp120 recognized by mouse 0.5 beta mAb. The best version (RL + RHe) of reshaped human 0.5 beta antibody had both binding affinity and neutralizing activity that were within twofold that of the mouse or chimeric 0.5 beta antibody.

Amino Acid Sequence↗

PubMed1991

Functional expression of furin demonstrating its intracellular localization and endoprotease activity for processing of proalbumin and complement pro-C3.

We have cloned a rat cDNA encoding furin which is structurally related to yeast Kex2 protease. Products of 88 and 94 kDa were obtained by in vitro transcription/translation of the cDNA in the absence and presence of microsomes. When the cDNA was transfected into COS-1 cells, furin was expressed as a major glycosylated form of 94 kDa, accompanied by a minor proteolytic form of 86 kDa, and found to be localized in the Golgi complex. Proalbumin and complement pro-C3 are intracellularly processed into their mature forms by cleavage at the dibasic residues Arg-Arg, a common cleavage signal found in many pro-type precursors. In cells transfected with the cDNA of C3 or albumin alone, only about half of each proform expressed was processed by an endogenous activity of the cells. When furin was coexpressed, the proforms of both C3 and albumin were completely processed into their mature forms. In addition, co-expression of rat alpha 1-protease inhibitor mutant (Met352----Arg) resulted in inhibition of the endogenous and exogenous processing activities, as observed for the naturally occurring mutant Pittsburgh which has been identified as a specific inhibitor for the processing enzyme. Taken together, these results indicate that furin is an endoprotease localized to the Golgi complex and capable of processing proalbumin and pro-C3 into the mature forms.

Amino Acid Sequence↗

PubMed1991

Review of the incidence and clinical relevance of myeloid antigen-positive acute lymphoblastic leukemia.

An increasing number of papers document cases of acute leukemia in which individual blast cells co-express markers normally restricted to a single cell lineage. Numerous terms are used to refer to cases with unscheduled expression of lineage-foreign proteins; the best defined categories were hybrid acute leukemia and acute mixed-lineage leukemia. The incidence of phenotypically variant acute leukemia varies with the quality and quantity of parameters used and the stringency of the criteria employed for its definition. Considerable interest has focused on acute lymphoblastic leukemia (ALL) cells expressing one or several myeloid lineage-associated antigens (My+ ALL), CD13, CD14, CD15, CD33, and CDw65. Owing to legitimate and cryptic expression on lymphoid cells, CD11b and CD15 reagents may not be considered as specific indicators of myeloid differentiation. The reported incidence ranged from 5 to 46% in 14 studies on My+ ALL, totalling 3817 patients. Several detailed reports documented a higher incidence of My+ ALL in adults (realistically in the range 10-20%) than in children (5-10%) and in B-lineage ALL as opposed to T-lineage ALL. My+ ALL cases are more likely to display unique cytogenetic [t(9;22), 11q23, 14q32] features than My-neg ALL. There appears to be no predominant expression of a single myeloid-associated antigen among those analyzed. As the morphological diagnosis of a leukemia subtype is often imprecise, some T-neg B-neg My+ ALL cases might actually contain FAB AML-M0 populations. While the expression of myeloid-associated antigens has no apparent prognostic significance in the majority of childhood ALL subtypes, in adults myeloid antigens seem to identify a high risk group of ALL patients with a poorer response to standard ALL therapy.

Adult↗

PubMedDate not supplied

Malignant sarcomatoid mesothelioma of the pleura: a histological and immunohistological study of a case.

The authors describe the case of a 70 year-old asymptomatic female, who showed nodular pleural growths at an occasional chest roentgenogram. Histological examinations and laboratory findings excluded the possibility of an inflammatory granulomatous process, but they did not allow differentiation between malignant sarcomatoid pleural mesothelioma and malignant fibrous histiocytoma. Only at immunohistochemistry was the differential diagnosis made. In fact, the co-expression of vimentin and cytokeratins by neoplastic cells, along with their negativity for macrophage markers strongly supported the hypothesis that the neoplastic growth originated from subpleural mesenchymal stem cells.

Aged↗

PubMed1991

[Recent advances in neuropsychopharmacology of the central histaminergic neuron system].

Recent immunohistochemical studies have shown the distribution of histaminergic neurons in the mammalian brain, which are concentrated in the tuberomammillary nucleus of the posterior hypothalamus and project efferent fibers to almost all parts of the brain from the olfactory bulb to the spinal cord. Histaminergic neurons co-express other neuroactive substances, such as gamma-aminobutyric acid, adenosine, substance P, galanin and Met-enkephalin-Arg-Phe. In addition, pharmacological studies have demonstrated the presence of presynaptic histamine H3-receptors (autoreceptor) in addition to H1- and H2-receptors. The specific agonist (alpha-methylhistamine) and antagonist (thioperamide) of H3-receptors were developed. Results from a number of studies indicate a variety of physiological roles of neuronal histamine such as thermoregulation, feeding behavior, sexual activity, sleep-wakefulness cycle, hormonal regulation and so on. Moreover, histaminergic drugs affect not only the emotional behavior, but also are effective to treat some patients of depression, Parkinson's disease, akathisia, motion sickness and so on. The central histaminergic neuron system is also affected by mental disorders and neuropsychopharmacological drugs. This review especially focused on these points and suggests that the central histaminergic neuron system may play an important role in the regulation of mental functions.

Animals↗

PubMed1990

The role and specificity of guanine nucleotide binding proteins in receptor-effector coupling.

Nine distinct alpha subunits of guanine nucleotide binding proteins (G-proteins) have now been identified by cDNA cloning. Each of these functions to allow transduction of information between hormone-activated receptors in the plasma membrane and effector systems which are either ion channels or enzymes which regulate the intracellular concentration of second messengers. As the individual G-proteins are highly similar in primary sequence, it is pertinent to ask what degree of specificity of interaction each of these display with the various receptors and effector systems. Specificity of tissue location defines that the rod and cone transducins (TD1 and TD2, respectively) act as the coupling proteins between rhodopsin and cone opsins and their cyclic nucleotide phosphodiesterase effectors and that G(olf) is the G-protein which tranduces signals from odorant receptors to adenylate cyclase in olfactory sensory neurones. However, many of the other identified G-proteins are co-expressed in a single tissue or cell. Whilst sensitivity to ADP-ribosylation catalysed by bacterial toxins from Bordetella pertussis and Vibrio cholerae has allowed a further subdivision of the G-protein family, this approach is limited as these toxins have multiple G-protein substrates. As the extreme C-terminus of the alpha subunit of each G-protein appears to be a key domain for the interactions of receptors and G-proteins we have generated a series of G-protein-selective antipeptide antisera against this region and then have used these antisera to attempt to interfere with receptor-G-protein coupling. With this approach we have been able to demonstrate that a delta opioid receptor-mediated inhibition of adenylate cyclase in neuroblastoma x glioma, NG108-15, cell membranes is transduced specifically by Gi2 and in the same cell that alpha 2 adrenergic inhibition of Ca2+ currents is transduced by Go. Similar strategies are likely to be of universal significance, for example in the identification of the G-protein (Gp) which regulates the receptor-mediated activation of phosphoinositidase C. Methods to allow pharmacological manipulation of the levels of expression of various G-proteins in the membranes of cells are also discussed. Such approaches are also likely to assist in the identification of G-proteins of defined functions.

Adenylyl Cyclases↗

PubMed1990

Identification of an isozymic form of acetyl-CoA carboxylase.

Acetyl-CoA carboxylase (ACC) is a major rate-limiting enzyme of fatty acid biosynthesis; its product, malonyl-CoA, also contributes to the regulation of fatty acid oxidation and elongation. Using monospecific antibodies directed against rat liver ACC and N- and C-terminal antipeptide antibodies raised against predicted sequences of the cloned ACC of Mr 265,000, we have identified a unique biotin-containing cytosolic protein of molecular mass 280,000 daltons that is distinct from this 265,000-dalton protein. This protein is uniquely expressed in rat cardiac and skeletal muscle but is co-expressed with the 265,000-dalton protein in rat liver, mammary gland, and brown adipose tissue. In the fed rat, white adipose tissue contains only the 265,000-dalton protein. Like the 265,000-dalton protein, the 280,000-dalton protein is present predominantly in the cytosolic fraction of liver. In the liver, the content of both proteins is diminished on fasting and increases on fasting/refeeding with a high carbohydrate diet. In contrast, the cardiac and skeletal muscle 280,000-dalton protein content is unaltered by nutritional manipulation. Avidin-Sepharose isolates of citrate-dependent ACC from the heart reveal only the 280,000-dalton protein, while white adipose tissue isolates show only the 265,000 form. These species differ in the sensitivity to citrate activation and in the Km for acetyl-CoA. Antibodies reactive with the 280,000-dalton protein on immunoblotting precipitate ACC activity in heart isolates, while white adipose ACC is precipitated only by antibodies specific for the 265,000-dalton species. However, in ACC isolates where both proteins are present, a heteroisozyme complex can be detected both by immunoprecipitation and by a sandwich enzyme-linked immunosorbent assay. We conclude that the 280,000-dalton protein is an isozyme of ACC, distinct from the previously cloned 265,000-dalton species. Its presence in cardiac and skeletal muscle, where fatty acid synthesis rates are low, suggest that it might play alternative roles in these tissues such as regulation of fatty acid oxidation or microsomal fatty acid elongation.

Acetyl-CoA Carboxylase↗

PubMed1990

Reconstitution of T-cell function after CD6-depleted allogeneic bone marrow transplantation.

Patients who undergo allogeneic bone marrow transplantation (BMT) are clinically immunodeficient for a prolonged period after engraftment. In the present study, we examined immune function after BMT in a series of patients who had received HLA compatible sibling marrow grafts purged of T cells with anti-CD6 monoclonal antibody and complement. None of the patients in this analysis received immunomodulating agents and none had developed graft-versus-host disease (GVHD). Initially after BMT, natural killer (NK) cells are the predominant cell type, giving way to CD3+, CD5+ T cells after 4 to 8 weeks. Despite the return of normal numbers of T lymphocytes post-BMT phenotypic analysis reveals several long-term abnormalities, including an inverted T4:T8 ratio and a significant fraction of CD3+ T cells that do not co-express CD6. In mitogenic assays, stimulation by either nonspecific lectin (phytohemagglutinin; PHA) or antibodies to the CD2 surface structure (anti-T11(2) + anti-T11(3)) results in decreased levels of T-cell proliferation compared with controls for over 18 months post-BMT. In contrast, the ability of unstimulated peripheral blood mononuclear cells (PBMC) to respond to recombinant interleukin-2 (rIL-2) is relatively intact, most likely reflecting early functional reconstitution of the NK cell population. To further characterize the prolonged abnormalities in T-cell proliferation after PHA or CD2 stimulation, we examined more proximal events in T-cell activation such as induction of IL-2 receptor expression and stimulus-induced intracellular calcium flux. We found that the induction of IL-2 receptor (p55) after in vitro activation, although initially abnormal, recovers completely by 6 months post-BMT. We also found that, after CD2 stimulation, calcium flux in T cells was normal immediately after engraftment. In contrast, after stimulation with anti-CD3 antibodies, a large population of T cells do not develop intracellular calcium flux compared with controls. We conclude that despite the recovery of normal numbers of T lymphocytes early after engraftment of CD6-depleted marrow, these T cells exhibit several physiologic and functional abnormalities that persist for varying intervals post-BMT. At present, it is unclear which of these specific defects is most closely associated with increased susceptibility to infectious agents after BMT.

Adolescent↗

PubMedDate not supplied

Immunohistochemical demonstration of growth factors, TGF-alpha, TGF-beta, IGF-I and neu oncogene product in benign and malignant human breast tissues.

The expression of growth factors, TGF-alpha, TGF-beta, IGF-I and neu oncogene product was studied immunohistochemically in the tissue of 120 benign and malignant human breasts. Growth factors were found only in benign or malignant mammary epithelial cells and not in stromal cells. Normal and benign lesions were found to be negative for reactivity with each antibody. Carcinoma in situ and invasive breast carcinomas demonstrated a significantly higher percentage of stained cells than that observed in benign lesions; forty (49%) of 82 invasive carcinomas were positive for TGF-alpha, 31 (38%) for TGF-beta, 31 (38%) for IGF-I and 34 (41%) for neu product. No overall correlations were found between expression of each growth factor and the clinical stage or degree of histologic differentiation of the carcinomas. A significant positive correlation was observed between ER status and IGF-I expression and between PgR status and TGF-beta expression. In the majority of the carcinomas, co-expression between TGF-alpha, TGF-beta and IGF-I was observed; the percentage of cases with parallel positive or negative expression of two growth factors was as follows; TGF-alpha - TGF-beta (70%), TGF-alpha - IGF-I (57%), TGF-beta - IGF-I (71%). The concomitant expression of TGF-alpha and neu oncogene product in cell surface was also observed. The relapse-free intervals of the patients were studied in association with expression of each growth factor. TGF-beta-positive tumors showed a significantly better prognosis than TGF-beta - negative tumors (within the first 2 years of observation). However, TGF-alpha, IGF-I and neu overexpression showed no effect on the prognosis of the patients.

Adult↗

PubMed1991

Expression of human HLA-B27 transgene alters susceptibility to murine Theiler's virus-induced demyelination.

Infection of certain strains of mice with Theiler's murine encephalomyelitis virus results in persistence of virus and an immune-mediated primary demyelination in the central nervous system that resembles multiple sclerosis. Because susceptibility/resistance to demyelination in B10 congeneic mice maps strongly to class I MHC genes (D region) we tested whether expression of a human class I MHC gene (HLA-B27) would alter susceptibility to Theiler's murine encephalomyelitis virus-induced demyelination. Transgenic HLA-B27 mice were found to co-express human and endogenous mouse class I MHC genes by flow microfluorimetry analysis of PBL. In the absence of the human transgene, H-2stf, or v mice but not H-2b mice had chronic demyelination and persistence of virus at 45 days after infection. No difference in degree of demyelination, meningeal inflammation, or virus persistence was seen between transgenic HLA-B27 and nontransgenic littermate mice of H-2f or H-2v haplotype. In contrast, H-2s (HLA-B27+) mice showed a dramatic decrease in extent of demyelination and number of virus-Ag+ cells in the spinal cord compared with H-2s (HLA-B27-) littermate mice. In addition, none of the eight H-2s mice homozygous for HLA-B27 gene had spinal cord lesions even though infectious virus was isolated chronically from their central nervous system. Expression of HLA-B27 transgene did not interfere with the resistance to demyelination normally observed in B10 (H-2b) mice. These experiments demonstrate that expression of a human class I MHC gene can modulate a virus-induced demyelinating disease process in the mouse.

Animals↗

PubMed1991

The alpha 2(VIII) collagen gene. A novel member of the short chain collagen family located on the human chromosome 1.

Type VIII collagen is a major component of Descemet's membrane, the specialized basement membrane of corneal endothelial cells. Sequence analysis of a cDNA isolated from a library made with mRNA from rabbit corneal endothelial cells has indicated that type VIII molecules contain a polypeptide chain, alpha 1(VIII), consisting of a short triple-helical domain of 454 amino acid residues flanked by non-triple-helical domains of 117 and 173 amino acid residues at the amino and carboxyl ends, respectively (Yamaguchi, N., Benya, P. D., van der Rest, M., and Ninomiya, Y. (1989) J. Biol. Chem. 264, 16022-16029). The sequence of alpha 1(VIII) is strikingly similar to that of alpha 1(X) collagen, a product of hypertrophic chondrocytes. Also, characterization of the alpha 1(VIII) and alpha 1(X) collagen genes has shown that they are quite similar in their exon organization. It has been concluded, therefore, that they are homologous members of a distinct subclass of collagen genes (Yamaguchi, N., Mayne, R., and Ninomiya, Y. (1991) J. Biol. Chem. 266, 4508-4513). We have given this subclass the name short chain collagens because of the relatively small size of the triple-helical domain. In the present study, we report on the identification and characterization of a collagen gene encoding a polypeptide which is co-expressed with the alpha 1(VIII) chain in corneal endothelial cells. This collagen chain contains a triple-helical and a carboxyl non-triple-helical domain encoded by a single, large exon both in mice and humans. We conclude, therefore, that the genes encodes a novel member of the short chain collagen family, and we have given this chain the designation alpha 2(VIII) collagen. By in situ hybridization we demonstrate that the alpha 2(VIII) gene is located in the p32.3-p34.3 region of the short arm of chromosome 1.

Amino Acid Sequence↗

PubMed1991

Phenotypic heterogeneity of intraepithelial T lymphocytes from mouse small intestine.

We have used two-colour flow cytometry to examine the heterogeneity of intraepithelial lymphocytes (IEL) from mouse small intestine. We have confirmed the predominance of CD3+ Thy 1- CD8+ IEL and show that a substantial but variable proportion of CD8+ IEL does not express the alpha beta T-cell receptor (TcR) for antigen. Simultaneous analysis of the co-expression of the alpha and beta chains of the CD8 heterodimer and of the alpha beta TcR revealed three populations of CD8+IEL. The first of these expressed both CD8 alpha and beta chains and had normal expression of V beta families and so represented conventional CD8+ alpha beta TcR+ T cells. The second population comprised alpha beta TcR- T cells (presumed gamma delta TcR+) which expressed only the alpha chain of the CD8 molecule. Finally, we identified a second, unique population of alpha beta TcR+ CD8+ IEL which were also CD8 beta-. Gamma delta + IEL predominated in mice aged less than 8 weeks, but there was a rapid increase in both populations of alpha beta TcR+ CD8+ IEL in older mice. CD8+ IEL were similar to peripheral CD8+ T cells in having high expression of the CD45RB molecule, but CD4+ IEL had generally lower expression of CD45RB than their peripheral counterparts, despite having normal expression of TcR. These findings emphasize the heterogeneity of IEL and underline the need to study phenotypically defined populations.

Aging↗

PubMed1991

High level expression of functional full length and truncated glucocorticoid receptor in Chinese hamster ovary cells. Demonstration of ligand-induced down-regulation of expressed receptor mRNA and protein.

Full length human glucocorticoid receptor and truncated receptor derivatives lacking the major amino-terminal trans-activating domain were expressed in stably transfected Chinese hamster ovary (CHO) cells. The receptors were co-expressed together with human metallothionein IIa, and the expression levels were amplified in the presence of increasing concentrations of metal. In amplified cells, both synthesized receptor forms showed the expected molecular weights, as assayed by affinity labeling and immunoblotting. They were expressed at concentrations of about 350,000-520,000 molecules/cell which corresponds to a 10-fold increase in receptor levels as compared to rat liver cells. The hormone (agonist or antagonist) binding properties of the expressed proteins were very similar to those characteristic of authentic glucocorticoid receptors in tissues or cultured cells. Moreover, the expressed proteins specifically recognized a glucocorticoid-response element sequence motif in in vitro protein-DNA binding experiments. The activation of a glucocorticoid-responsive reporter gene by the expressed full length receptor was dramatic (about 75-fold) and strictly ligand-dependent. In contrast, the expressed amino-terminal deletion mutant exhibited considerably weaker functional activity but showed normal hormone-binding properties. Upon exposure to dexamethasone in vivo, the expressed receptor mRNAs and proteins were down-regulated about 2- to 6-fold, indicating that regulatory signals important for autoregulation may be contained within structures corresponding to the ligand and DNA-binding domains. Transcription from the expression vector was not negatively regulated from the hormone, strongly arguing that receptor down-regulation was due to a post-transcriptional mechanism. In conclusion, this expression system should be a useful tool for further structural and functional studies of the receptor, including the biochemistry of its activation from a cryptic to a functional species, and its ligand-dependent autoregulation.

Affinity Labels↗