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Caldwell CC, Kojima H, Lukashev D, Armstrong J, Farber M, Apasov SG, Sitkovsky MV. Differential effects of physiologically relevant hypoxic conditions on T lymphocyte development and effector functions. J Immunol 2001; 167:6140-9. [PMID: 11714773 DOI: 10.4049/jimmunol.167.11.6140] [Citation(s) in RCA: 304] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Direct measurements revealed low oxygen tensions (0.5-4.5% oxygen) in murine lymphoid organs in vivo. To test whether adaptation to changes in oxygen tension may have an effect on lymphocyte functions, T cell differentiation and functions at varying oxygen tensions were studied. These studies show: 1) differentiated CTL deliver Fas ligand- and perforin-dependent lethal hit equally well at all redox conditions; 2) CTL development is delayed at 2.5% oxygen as compared with 20% oxygen. Remarkably, development of CTL at 2.5% oxygen is more sustained and the CTL much more lytic; and 3) hypoxic exposure and TCR-mediated activation are additive in enhancing levels of hypoxia response element-containing gene products in lymphocyte supernatants. In contrast, hypoxia inhibited the accumulation of nonhypoxia response element-containing gene products (e.g., IL-2 and IFN-gamma) in the same cultures. This suggests that T cell activation in hypoxic conditions in vivo may lead to different patterns of lymphokine secretion and accumulation of cytokines (e.g., vascular endothelial growth factor) affecting endothelial cells and vascular permeabilization. Thus, although higher numbers of cells survive and are activated during 20% oxygen incubation in vitro, the CTL which develop at 2.5% oxygen are more lytic with higher levels of activation markers. It is concluded that the ambient 20% oxygen tension (plus 2-ME) is remarkably well suited for immunologic specificity and cytotoxicity studies, but oxygen dependence should be taken into account during the design and interpretation of results of in vitro T cell development assays and gene expression studies in vivo.
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MESH Headings
- Animals
- CD8-Positive T-Lymphocytes/cytology
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/metabolism
- Cell Differentiation/genetics
- Cell Differentiation/immunology
- Cell Hypoxia/genetics
- Cell Hypoxia/immunology
- Cells, Cultured
- Cytokines/metabolism
- Cytotoxicity, Immunologic/genetics
- DNA-Binding Proteins/genetics
- Fas Ligand Protein
- Hypoxia-Inducible Factor 1
- Hypoxia-Inducible Factor 1, alpha Subunit
- Ligands
- Lymphocyte Count
- Lymphocyte Culture Test, Mixed
- Lymphocyte Function-Associated Antigen-1/metabolism
- Lymphoid Tissue/cytology
- Lymphoid Tissue/metabolism
- Membrane Glycoproteins/toxicity
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Nuclear Proteins/genetics
- Oxygen/metabolism
- Oxygen/physiology
- Perforin
- Pore Forming Cytotoxic Proteins
- Receptor-CD3 Complex, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/physiology
- Response Elements/immunology
- T-Lymphocyte Subsets/cytology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- T-Lymphocytes, Cytotoxic/cytology
- T-Lymphocytes, Cytotoxic/immunology
- T-Lymphocytes, Cytotoxic/metabolism
- Transcription Factors
- fas Receptor/metabolism
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Affiliation(s)
- C C Caldwell
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1892, USA
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Apasov SG, Blackburn MR, Kellems RE, Smith PT, Sitkovsky MV. Adenosine deaminase deficiency increases thymic apoptosis and causes defective T cell receptor signaling. J Clin Invest 2001; 108:131-41. [PMID: 11435465 PMCID: PMC209335 DOI: 10.1172/jci10360] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Adenosine deaminase (ADA) deficiency in humans results in a severe combined immunodeficiency (SCID). This immunodeficiency is associated with severe disturbances in purine metabolism that are thought to mediate lymphotoxicity. The recent generation of ADA-deficient (ADA(-/-)) mice has enabled the in vivo examination of mechanisms that may underlie the SCID resulting from ADA deficiency. We demonstrate severe depletion of T and B lymphocytes and defects in T and B cell development in ADA(-/-) mice. T cell apoptosis was abundant in thymi of ADA(-/-) mice, but no increase in apoptosis was detected in the spleen and lymph nodes of these animals, suggesting that the defect is specific to developing thymocytes. Studies of mature T cells recovered from spleens of ADA(-/-) mice revealed that ADA deficiency is accompanied by TCR activation defects of T cells in vivo. Furthermore, ex vivo experiments on ADA(-/-) T cells demonstrated that elevated adenosine is responsible for this abnormal TCR signaling. These findings suggest that the metabolic disturbances seen in ADA(-/-) mice affect various signaling pathways that regulate thymocyte survival and function. Experiments with thymocytes ex vivo confirmed that ADA deficiency reduces tyrosine phosphorylation of TCR-associated signaling molecules and blocks TCR-triggered calcium increases.
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MESH Headings
- Adenosine/pharmacology
- Adenosine Deaminase/deficiency
- Animals
- Antigens, CD/biosynthesis
- Antigens, CD/genetics
- Antigens, Differentiation, T-Lymphocyte/biosynthesis
- Antigens, Differentiation, T-Lymphocyte/genetics
- Apoptosis
- B-Lymphocytes/pathology
- Calcium Signaling
- Cell Differentiation
- Cells, Cultured
- Deoxyadenine Nucleotides/metabolism
- Deoxyadenosines/pharmacology
- Gene Expression Regulation
- Lectins, C-Type
- Lymph Nodes/immunology
- Lymph Nodes/pathology
- Lymphocyte Activation
- Mice
- Mice, Knockout
- Mice, SCID
- Organ Specificity
- Phosphorylation
- Protein Processing, Post-Translational
- Receptor-CD3 Complex, Antigen, T-Cell/immunology
- Receptor-CD3 Complex, Antigen, T-Cell/metabolism
- Receptors, Interleukin-2/biosynthesis
- Receptors, Interleukin-2/genetics
- Severe Combined Immunodeficiency/genetics
- Severe Combined Immunodeficiency/immunology
- Severe Combined Immunodeficiency/pathology
- Signal Transduction
- Specific Pathogen-Free Organisms
- Spleen/immunology
- Spleen/pathology
- T-Lymphocytes/drug effects
- T-Lymphocytes/immunology
- T-Lymphocytes/pathology
- Thymus Gland/drug effects
- Thymus Gland/pathology
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Affiliation(s)
- S G Apasov
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland 20892, USA
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Apasov SG, Sitkovsky MV. The extracellular versus intracellular mechanisms of inhibition of TCR-triggered activation in thymocytes by adenosine under conditions of inhibited adenosine deaminase. Int Immunol 1999; 11:179-89. [PMID: 10069416 DOI: 10.1093/intimm/11.2.179] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The absence or low levels of adenosine deaminase (ADA) in humans result in severe combined immunodeficiency (SCID), which is characterized by hypoplastic thymus, T lymphocyte depletion and autoimmunity. Deficiency of ADA causes increased levels of both intracellular and extracellular adenosine, although only the intracellular lymphotoxicity of accumulated adenosine is considered in the pathogenesis of ADA SCID. It is shown that extracellular but not intracellular adenosine selectively inhibits TCR-triggered up-regulation of activation markers and apoptotic events in thymocytes under conditions of ADA deficiency. The effects of intracellular adenosine are dissociated from effects of extracellular adenosine in experiments using an adenosine transporter blocker. We found that prevention of toxicity of intracellular adenosine led to survival of TCR-cross-linked thymocytes in long-term (4 days) assays, but it was not sufficient for normal T cell differentiation under conditions of inhibited ADA. Surviving TCR-cross-linked thymocytes had a non-activated phenotype due to extracellular adenosine-mediated, TCR-antagonizing signaling. Taken together the data suggest that both intracellular toxicity and signaling by extracellular adenosine may contribute to pathogenesis of ADA SCID. Accordingly, extracellular adenosine may act on thymocytes, which survived intracellular toxicity of adenosine during ADA deficiency by counteracting TCR signaling. This, in turn, could lead to failure of positive and negative selection of thymocytes, and to additional elimination of thymocytes or autoimmunity of surviving T cells.
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Affiliation(s)
- S G Apasov
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1892, USA
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Apasov SG, Koshiba M, Chused TM, Sitkovsky MV. Effects of extracellular ATP and adenosine on different thymocyte subsets: possible role of ATP-gated channels and G protein-coupled purinergic receptor. The Journal of Immunology 1997. [DOI: 10.4049/jimmunol.158.11.5095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
To explore the possible role of purinergic receptors in thymocyte development and in pathogenesis of adenosine deaminase SCID, we studied effects of extracellular adenosine triphosphate (ATP(ext)) and adenosine on TCR- and steroid hormone-triggered processes in mouse thymocytes. Reverse transcriptase-PCR analysis confirms the mRNA expression of several types of purinergic receptors, while the functioning of ATP receptors in thymocytes is reflected by ATP(ext)-induced intracellular calcium increases and by thymocyte subset-specific sensitivity to the effects of ATP(ext) and adenosine. Only ATP(ext), but not the ATP catabolites, adenosine, dexamethasone, or TCR cross-linking, was efficient in triggering rapid protein synthesis independent lysis of CD4+8- thymocytes and peripheral CD4+ T cells. In contrast, extracellular adenosine specifically induced the apoptosis of CD4+8+ thymocytes. ATP(ext) also induced a slower process of DNA fragmentation and protein synthesis-dependent apoptosis in all thymocyte subsets. ATP(ext) had an additive effect with TCR cross-linking in the induction of thymocyte death, but, unexpectedly, the effects of ATP(ext) at high concentration were antagonistic to steroid-induced apoptosis. Described here, the properties of ATP(ext) and adenosine are consistent with their involvement in the regulation of T cell development due to differential expression and signaling through purinergic receptors in different thymocyte subsets. The possible role of purinergic receptor signaling in T cell differentiation and adenosine deaminase SCID is discussed.
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Affiliation(s)
- S G Apasov
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - M Koshiba
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - T M Chused
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - M V Sitkovsky
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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Apasov SG, Koshiba M, Chused TM, Sitkovsky MV. Effects of extracellular ATP and adenosine on different thymocyte subsets: possible role of ATP-gated channels and G protein-coupled purinergic receptor. J Immunol 1997; 158:5095-105. [PMID: 9164924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
To explore the possible role of purinergic receptors in thymocyte development and in pathogenesis of adenosine deaminase SCID, we studied effects of extracellular adenosine triphosphate (ATP(ext)) and adenosine on TCR- and steroid hormone-triggered processes in mouse thymocytes. Reverse transcriptase-PCR analysis confirms the mRNA expression of several types of purinergic receptors, while the functioning of ATP receptors in thymocytes is reflected by ATP(ext)-induced intracellular calcium increases and by thymocyte subset-specific sensitivity to the effects of ATP(ext) and adenosine. Only ATP(ext), but not the ATP catabolites, adenosine, dexamethasone, or TCR cross-linking, was efficient in triggering rapid protein synthesis independent lysis of CD4+8- thymocytes and peripheral CD4+ T cells. In contrast, extracellular adenosine specifically induced the apoptosis of CD4+8+ thymocytes. ATP(ext) also induced a slower process of DNA fragmentation and protein synthesis-dependent apoptosis in all thymocyte subsets. ATP(ext) had an additive effect with TCR cross-linking in the induction of thymocyte death, but, unexpectedly, the effects of ATP(ext) at high concentration were antagonistic to steroid-induced apoptosis. Described here, the properties of ATP(ext) and adenosine are consistent with their involvement in the regulation of T cell development due to differential expression and signaling through purinergic receptors in different thymocyte subsets. The possible role of purinergic receptor signaling in T cell differentiation and adenosine deaminase SCID is discussed.
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Affiliation(s)
- S G Apasov
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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Apasov SG, Smith PT, Jelonek MT, Margulies DH, Sitkovsky MV. Phosphorylation of extracellular domains of T-lymphocyte surface proteins. Constitutive serine and threonine phosphorylation of the T cell antigen receptor ectodomains. J Biol Chem 1996; 271:25677-83. [PMID: 8810345 DOI: 10.1074/jbc.271.41.25677] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The extracellular accumulation of ATP after activation of T-lymphocytes, as well as the presence of ecto-protein kinases in these cells, led us to propose that T cell surface receptors could be regulated through the reversible phosphorylation of their extracellular domains (ectodomains). Here, in a model system, we used T cell transfectants which express T cell antigen receptor chains lacking intracellular and transmembrane protein domains and 32Pi metabolic labeling of cells to definitively demonstrate phosphorylation of ectodomains of T cell surface proteins. We show that alphabetaTCR ectodomains were phosphorylated intracellularly and constitutively on serine and threonine residues and were then expressed on the T cell surface in phosphorylated form. TCR ectodomains also could be phosphorylated at the cell surface when extracellular [gamma-32P]ATP or [gamma-32P]GTP were used as phosphate donors with the same cells. Consensus phosphorylation sites for serine and threonine protein kinases were found to be strongly evolutionary conserved in both alpha and beta TCR chains constant regions. These results are consistent with the hypothesis, where T cell surface proteins which are phosphorylated intracellularly on their ectodomains, could subsequently be expressed at the cell surface and then be reversibly modified by ectoprotein phosphatase(s) and by ectokinase(s). Such modifications may change T cells cognate interactions by, e.g. affecting TCR-multimolecular complex formation and antigen binding affinity. It is suggested that alphabetaTCR ectodomain phosphorylation could serve as a potential mechanism for regulation of alphabetaTCR-mediated T-lymphocytes response.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Amino Acid Sequence
- Antibodies, Monoclonal
- Biological Evolution
- Cell Line
- Conserved Sequence
- Guanosine Triphosphate/metabolism
- Humans
- Lymphoma
- Membrane Proteins/chemistry
- Membrane Proteins/metabolism
- Phosphates/metabolism
- Phosphoprotein Phosphatases/metabolism
- Phosphorus Radioisotopes
- Phosphorylation
- Phosphoserine/analysis
- Phosphothreonine/analysis
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
- Tumor Cells, Cultured
- Type C Phospholipases/metabolism
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Affiliation(s)
- S G Apasov
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-1892, USA
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Apasov SG, Sitkovsky MV. Development and antigen specificity of CD8+ cytotoxic T lymphocytes in beta 2-microglobulin-negative, MHC class I-deficient mice in response to immunization with tumor cells. J Immunol 1994; 152:2087-97. [PMID: 8133027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
beta 2-Microglobulin knockout mice (beta 2-m-/-) with MHC class I expression deficiency are able to develop functional TCR(+)-alpha beta, CD8+ CTLs in response to tumor cell injection. The i.p. injection of beta 2-m-/- mice with tumor results in the massive accumulation of highly lytic CD8+ CTLs in the peritoneum and causes the local recruitment of CD8+ T cells into lymph nodes and spleens of immune animals. The accumulation of CD8+ CTLs in peritoneum is accompanied by the rejection of tumor cells and the survival of animals. The deficiency in MHC class I expression in beta 2-m/- mice is reflected in the delayed tumor rejection and CD8+ cell accumulation during the primary anti-tumor response in comparison with normal mice. The secondary response, however, is identical in normal and MHC class I-deficient mice. The rejection of tumor cells appears to be MHC class I directed because no rejection of tumors, no accumulation of CD8+ CTLs, and no survival of animals were observed when syngeneic tumor cells were used for injection with the notable exception of anti-minor Ag response. The Ag specificity of CD8+ CTLs in beta 2-m-/- mice is demonstrated using a panel of tumor target cells and class I transfectants. Although no substantial differences were found in the number and specificity of peritoneal CD8+ CTLs in beta 2-m-/- and normal mice using tumor rejection studies, the analysis of TCR-V beta phenotype using the panel of mAbs revealed the reduction in proportion of TCR-V beta 5 and TCR-V beta 6 used by CD8+ cell population from beta 2-m-/- mice. Development of lytic and H-2-directed CD8+ cells in regional lymph nodes was also observed after footpad immunization of beta 2-m-/- mice with TNP-labeled C57BL/6 splenocytes, suggesting anti-minor Ag reaction.
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MESH Headings
- Animals
- Cytotoxicity, Immunologic
- Graft Rejection/immunology
- H-2 Antigens/genetics
- Immunization
- Immunization, Secondary
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Knockout
- Minor Histocompatibility Antigens
- Neoplasm Transplantation
- Receptors, Antigen, T-Cell, alpha-beta
- T-Lymphocytes, Cytotoxic/immunology
- Tumor Cells, Cultured/immunology
- beta 2-Microglobulin/deficiency
- beta 2-Microglobulin/genetics
- beta 2-Microglobulin/immunology
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Affiliation(s)
- S G Apasov
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
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Apasov SG, Sitkovsky MV. Development and antigen specificity of CD8+ cytotoxic T lymphocytes in beta 2-microglobulin-negative, MHC class I-deficient mice in response to immunization with tumor cells. The Journal of Immunology 1994. [DOI: 10.4049/jimmunol.152.5.2087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
beta 2-Microglobulin knockout mice (beta 2-m-/-) with MHC class I expression deficiency are able to develop functional TCR(+)-alpha beta, CD8+ CTLs in response to tumor cell injection. The i.p. injection of beta 2-m-/- mice with tumor results in the massive accumulation of highly lytic CD8+ CTLs in the peritoneum and causes the local recruitment of CD8+ T cells into lymph nodes and spleens of immune animals. The accumulation of CD8+ CTLs in peritoneum is accompanied by the rejection of tumor cells and the survival of animals. The deficiency in MHC class I expression in beta 2-m/- mice is reflected in the delayed tumor rejection and CD8+ cell accumulation during the primary anti-tumor response in comparison with normal mice. The secondary response, however, is identical in normal and MHC class I-deficient mice. The rejection of tumor cells appears to be MHC class I directed because no rejection of tumors, no accumulation of CD8+ CTLs, and no survival of animals were observed when syngeneic tumor cells were used for injection with the notable exception of anti-minor Ag response. The Ag specificity of CD8+ CTLs in beta 2-m-/- mice is demonstrated using a panel of tumor target cells and class I transfectants. Although no substantial differences were found in the number and specificity of peritoneal CD8+ CTLs in beta 2-m-/- and normal mice using tumor rejection studies, the analysis of TCR-V beta phenotype using the panel of mAbs revealed the reduction in proportion of TCR-V beta 5 and TCR-V beta 6 used by CD8+ cell population from beta 2-m-/- mice. Development of lytic and H-2-directed CD8+ cells in regional lymph nodes was also observed after footpad immunization of beta 2-m-/- mice with TNP-labeled C57BL/6 splenocytes, suggesting anti-minor Ag reaction.
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Affiliation(s)
- S G Apasov
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - M V Sitkovsky
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
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Fedoseyeva EV, Apasov SG, Chervonsky AV. Specific T suppressors and cytotoxic T lymphocytes recognize different epitopes on Abbm12 molecule. Immunogenetics 1990; 32:129-33. [PMID: 1697846 DOI: 10.1007/bf00210450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Neyfakh AA, Serpinskaya AS, Chervonsky AV, Apasov SG, Kazarov AR. Multidrug-resistance phenotype of a subpopulation of T-lymphocytes without drug selection. Exp Cell Res 1989; 185:496-505. [PMID: 2480910 DOI: 10.1016/0014-4827(89)90318-2] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Multidrug-resistant (MDR) cells demonstrate the increased activity of the membrane transport system performing efflux of diverse lipophylic drugs and fluorescent dyes from the cells. In order to detect MDR cells we have developed a simple test consisting of three steps: staining of the cells with fluorescent dye rhodamine 123, incubation in the dye-free medium and, finally, detection by fluorescence microscopy of the cells that have lost accumulated dye. The experiments with B-lymphoma cell lines with different degrees of MDR have shown that the cell fluorescence after the poststaining incubation is indeed inversely proportional to the degree of resistance. Application of this testing procedure to normal human or mouse leukocytes revealed the presence of the cells rapidly losing the dye in these populations. Cell fractionation experiments have shown that there are T-lymphocytes (most T-killers/suppressors and a part of T-helpers) that demonstrate rapid efflux of rhodamine 123. This characteristic was detected also in T-killer clones and cell line and in some T-lymphomas. The inhibitors of the MDR transport system, reserpine and verapamil, blocked the efflux of the dye from these cells. Rhodamine-losing T-lymphoma contained large amounts of the mRNA coding P-glycoprotein, the MDR efflux pump, and demonstrated increased resistance to rhodamine 123, gramicidin D, colchicine, and vincristine, the drugs belonging to the cross-resistance group for the MDR cells. The role of the increased activity of the MDR membrane transport system in T-lymphocytes is discussed.
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Affiliation(s)
- A A Neyfakh
- Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, USSR
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