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Jackman RP, Darst O, Gaillard B, Tran JQ, Tomayko MM, Muench MO. Enhanced alloresponse to platelet transfusion due to immune dysregulation following ablative chemotherapy in mice. Front Immunol 2023; 14:1281123. [PMID: 38090570 PMCID: PMC10711281 DOI: 10.3389/fimmu.2023.1281123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 11/07/2023] [Indexed: 12/18/2023] Open
Abstract
Introduction Alloimmunization is common following platelet transfusion and can result in negative outcomes for recipients such as refractoriness to subsequent transfusions and rejection of transplants. Healthy people do not receive blood transfusions, and the diseases and therapies that result in a need to transfuse have significant impacts on the immunological environment to which these alloantigens are introduced. Ablative chemotherapies are common among platelet recipients and have potent immunological effects. In this study, we modeled the impact of chemotherapy on the alloresponse to platelet transfusion. As chemotherapies are generally regarded as immunosuppressive, we hypothesized that that they would result in a diminished alloresponse. Methods Mice were given a combination chemotherapeutic treatment of cytarabine and doxorubicin followed by transfusion of allogeneic platelets, and compared to controls given no treatment, chemotherapy alone, or transfusion alone. Alloantibody responses were measured 2 weeks after transfusion, and cellular responses and growth factors were monitored over time. Results Contrary to our hypothesis, we found that chemotherapy led to increased alloantibody responses to allogeneic platelet transfusion. This enhanced response was antigen-specific and was associated with increased CD4+ and CD8+ T cell responses. Chemotherapy led to rapid lymphocyte depletion followed by reconstitution, non-specific activation of transitional B cells with the highest levels of activation in the least mature subsets, and increased serum levels of B cell activating factor (BAFF). Conclusion These data suggest that ablative chemotherapy can increase the risk of alloimmunization and, if confirmed clinically, that additional measures to protect these patient populations may be warranted.
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Affiliation(s)
- Rachael P. Jackman
- Vitalant Research Institute, San Francisco, CA, United States
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Orsolya Darst
- Vitalant Research Institute, San Francisco, CA, United States
| | - Betty Gaillard
- Vitalant Research Institute, San Francisco, CA, United States
| | - Johnson Q. Tran
- Vitalant Research Institute, San Francisco, CA, United States
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Mary M. Tomayko
- Department of Dermatology, Yale School of Medicine, New Haven, CT, United States
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States
| | - Marcus O. Muench
- Vitalant Research Institute, San Francisco, CA, United States
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA, United States
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2
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Sponaugle A, Weideman AMK, Ranek J, Atassi G, Kuruc J, Adimora AA, Archin NM, Gay C, Kuritzkes DR, Margolis DM, Vincent BG, Stanley N, Hudgens MG, Eron JJ, Goonetilleke N. Dominant CD4 + T cell receptors remain stable throughout antiretroviral therapy-mediated immune restoration in people with HIV. Cell Rep Med 2023; 4:101268. [PMID: 37949070 PMCID: PMC10694675 DOI: 10.1016/j.xcrm.2023.101268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 06/05/2023] [Accepted: 10/10/2023] [Indexed: 11/12/2023]
Abstract
In people with HIV (PWH), the post-antiretroviral therapy (ART) window is critical for immune restoration and HIV reservoir stabilization. We employ deep immune profiling and T cell receptor (TCR) sequencing and examine proliferation to assess how ART impacts T cell homeostasis. In PWH on long-term ART, lymphocyte frequencies and phenotypes are mostly stable. By contrast, broad phenotypic changes in natural killer (NK) cells, γδ T cells, B cells, and CD4+ and CD8+ T cells are observed in the post-ART window. Whereas CD8+ T cells mostly restore, memory CD4+ T subsets and cytolytic NK cells show incomplete restoration 1.4 years post ART. Surprisingly, the hierarchies and frequencies of dominant CD4 TCR clonotypes (0.1%-11% of all CD4+ T cells) remain stable post ART, suggesting that clonal homeostasis can be independent of homeostatic processes regulating CD4+ T cell absolute number, phenotypes, and function. The slow restoration of host immunity post ART also has implications for the design of ART interruption studies.
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Affiliation(s)
- Alexis Sponaugle
- Department of Microbiology & Immunology, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Ann Marie K Weideman
- Department of Biostatistics, UNC Chapel Hill, Chapel Hill, NC, USA; Center for AIDS Research, School of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Jolene Ranek
- Computational Medicine Program, UNC Chapel Hill, Chapel Hill, NC, USA; Curriculum in Bioinformatics and Computational Biology, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Gatphan Atassi
- Lineberger Comprehensive Cancer Center, UNC Chapel Hill, Chapel Hill, NC, USA
| | - JoAnn Kuruc
- Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Adaora A Adimora
- Center for AIDS Research, School of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA; Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA; Department of Epidemiology, Gillings School of Global Public Health, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Nancie M Archin
- Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Cynthia Gay
- Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Daniel R Kuritzkes
- Division of Infectious Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - David M Margolis
- Department of Microbiology & Immunology, UNC Chapel Hill, Chapel Hill, NC, USA; Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Benjamin G Vincent
- Department of Microbiology & Immunology, UNC Chapel Hill, Chapel Hill, NC, USA; Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA; Curriculum in Bioinformatics and Computational Biology, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Natalie Stanley
- Computational Medicine Program, UNC Chapel Hill, Chapel Hill, NC, USA; Department of Computer Science, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Michael G Hudgens
- Department of Biostatistics, UNC Chapel Hill, Chapel Hill, NC, USA; Center for AIDS Research, School of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Joseph J Eron
- Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Nilu Goonetilleke
- Department of Microbiology & Immunology, UNC Chapel Hill, Chapel Hill, NC, USA; Department of Medicine, UNC Chapel Hill, Chapel Hill, NC, USA.
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3
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Zhao J, Wang X, He Y, Xu P, Lai L, Chung Y, Pan X. The Role of T Cells in Alzheimer's Disease Pathogenesis. Crit Rev Immunol 2023; 43:15-23. [PMID: 37943150 DOI: 10.1615/critrevimmunol.2023050145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with memory decline and cognitive impairment, which is related to hallmark protein aggregates, amyloid-β (Аβ) plaques and neurofibrillary tangles; the latter are accumulated with hyperphosphorylated Tau protein. Immune cells play an important role in AD pathogenesis. Although the role of T cells in AD remains controversial, studies have shown that T cell deficiency is associated with increased AD pathology. In contrast, transplantation of T cells reduces AD pathology. T cells can help B cells generate anti-Аβ antibody to neutralize the toxin of Аβ and hyperphosphorylated Tau. T cells also activate macrophages to phagocytose misfolded proteins including Аβ and Tau. Recent data have also shown that AD animals have a damaged thymic microenvironment, especially thymic epithelial cells (TECs), resulting in decreased T cell numbers, which contribute to AD pathology. Therefore, regulation of T cell regeneration, for example by rejuvenating the thymic microenvironment, has the potential to be used in the treatment of AD.
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Affiliation(s)
- Jin Zhao
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, and Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong, 510515, China; ZhuHai Hengqin ImStem Biotechnology Co. Ltd., Hengqin New District Huandao Donglu 1889 Building 3, Zhuhai, Guangdong, 519000, China; Key Laboratory of Mental Health of the Ministry of Education, Guangdong Province Key Laboratory of Psychiatric Disorders, School of Basic Medical Sciences, Southern Medical University, Guangdong, 510515, China
| | - Xiaofang Wang
- ZhuHai Hengqin ImStem Biotechnology Co. Ltd., Hengqin New District Huandao Donglu 1889 Building 3, Zhuhai, Guangdong, 519000, China; ImStem Biotechnology, Inc., 400 Farmington Avenue R1808, Farmington, CT 06030, USA
| | - Yusheng He
- ZhuHai Hengqin ImStem Biotechnology Co. Ltd., Hengqin New District Huandao Donglu 1889 Building 3, Zhuhai, Guangdong, 519000, China
| | - Pingyi Xu
- Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, 510120, China
| | - Laijun Lai
- Department of Allied Health Sciences, University of Connecticut, Storrs, CT, USA; University of Connecticut Stem Cell Institute, University of Connecticut, Storrs, CT, USA
| | - Younggie Chung
- ZhuHai Hengqin ImStem Biotechnology Co. Ltd., Hengqin New District Huandao Donglu 1889 Building 3, Zhuhai, Guangdong, 519000, China; ImStem Biotechnology, Inc., 400 Farmington Avenue R1808, Farmington, CT 06030, USA
| | - Xinghua Pan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, and Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong, 510515, China; Key Laboratory of Mental Health of the Ministry of Education, Guangdong Province Key Laboratory of Psychiatric Disorders, School of Basic Medical Sciences, Southern Medical University, Guangdong, 510515, China
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4
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Hino C, Xu Y, Xiao J, Baylink DJ, Reeves ME, Cao H. The potential role of the thymus in immunotherapies for acute myeloid leukemia. Front Immunol 2023; 14:1102517. [PMID: 36814919 PMCID: PMC9940763 DOI: 10.3389/fimmu.2023.1102517] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Accepted: 01/20/2023] [Indexed: 02/09/2023] Open
Abstract
Understanding the factors which shape T-lymphocyte immunity is critical for the development and application of future immunotherapeutic strategies in treating hematological malignancies. The thymus, a specialized central lymphoid organ, plays important roles in generating a diverse T lymphocyte repertoire during the infantile and juvenile stages of humans. However, age-associated thymic involution and diseases or treatment associated injury result in a decline in its continuous role in the maintenance of T cell-mediated anti-tumor/virus immunity. Acute myeloid leukemia (AML) is an aggressive hematologic malignancy that mainly affects older adults, and the disease's progression is known to consist of an impaired immune surveillance including a reduction in naïve T cell output, a restriction in T cell receptor repertoire, and an increase in frequencies of regulatory T cells. As one of the most successful immunotherapies thus far developed for malignancy, T-cell-based adoptive cell therapies could be essential for the development of a durable effective treatment to eliminate residue leukemic cells (blasts) and prevent AML relapse. Thus, a detailed cellular and molecular landscape of how the adult thymus functions within the context of the AML microenvironment will provide new insights into both the immune-related pathogenesis and the regeneration of a functional immune system against leukemia in AML patients. Herein, we review the available evidence supporting the potential correlation between thymic dysfunction and T-lymphocyte impairment with the ontogeny of AML (II-VI). We then discuss how the thymus could impact current and future therapeutic approaches in AML (VII). Finally, we review various strategies to rejuvenate thymic function to improve the precision and efficacy of cancer immunotherapy (VIII).
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Affiliation(s)
- Christopher Hino
- Department of Internal Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Yi Xu
- Division of Hematology and Oncology, Department of Medicine, Loma Linda University, Loma Linda, CA, United States.,Division of Regenerative Medicine, Department of Medicine, Loma Linda University, Loma Linda, CA, United States.,Loma Linda University Cancer Center, Loma Linda, CA, United States
| | - Jeffrey Xiao
- Division of Regenerative Medicine, Department of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - David J Baylink
- Division of Regenerative Medicine, Department of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Mark E Reeves
- Division of Hematology and Oncology, Department of Medicine, Loma Linda University, Loma Linda, CA, United States.,Loma Linda University Cancer Center, Loma Linda, CA, United States
| | - Huynh Cao
- Division of Hematology and Oncology, Department of Medicine, Loma Linda University, Loma Linda, CA, United States.,Loma Linda University Cancer Center, Loma Linda, CA, United States
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Emens LA, Reilly RT, Jaffee EM. Cancer vaccines in combination with multimodality therapy. Cancer Treat Res 2005; 123:227-45. [PMID: 16211873 DOI: 10.1007/0-387-27545-2_10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Affiliation(s)
- Leisha A Emens
- The Johns Hopkins University School of Medicine, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Bunting-Blaustein Cancer Research Building, 1650 Orleans Street, Room 4M90 Baltimore, Maryland 21231-1000, USA.
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Dainiak N, Waselenko JK, Armitage JO, MacVittie TJ, Farese AM. The hematologist and radiation casualties. HEMATOLOGY. AMERICAN SOCIETY OF HEMATOLOGY. EDUCATION PROGRAM 2003; 2003:473-496. [PMID: 14633795 DOI: 10.1182/asheducation-2003.1.473] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Since the terrorist attack of September 11, 2001, preparation by the health care system for an act of terrorism has been mandated by leaders of governments. Scenarios for terrorist acts involving radioactive material have been identified, and approaches to management (based on past experience from atomic weapons detonations and radiation accidents) have been developed. Because of their experience in managing patients with profound cytopenia and/or marrow aplasia, hematologists will be asked to play a significant role in evaluating and treating victims of mass accidental or deliberate exposure to radiation. This review provides a framework for understanding how radiation levels are quantified, how radiation alters the function of hematopoietic (and nonhematopoietic) cells and tissues, and how victims receiving a significant radiation dose can be identified and managed. In Section I, Dr. Nicholas Dainiak reviews four components of the Acute Radiation Syndrome: the hematopoietic, neurovascular, gastrointestinal and cutaneous subsyndromes. Clinical signs and symptoms are discussed for exposed individuals at the time of initial presentation (the prodromal phase) and during their course of disease (the manifest illness). In Section II, he presents clinical and laboratory methods to assess radiation doses, including time to onset and severity of vomiting, rate of decline in absolute blood lymphocyte count and the appearance of chromosome aberrations such as dicentrics and ring forms. Potential scenarios of a radiation terrorist event are reviewed, and methods for initial clinical assessment, triage, and early management of the acute radiation syndrome and its component subsyndromes are summarized. In Section III, Dr. Jamie Waselenko reviews the hematopoietic syndrome, and presents guidelines for the use of cytokine therapy, antibiotics, and supportive care that have been developed by the Strategic National Pharmaceutical Stockpile Working Group. Results of preclinical and clinical growth factor therapy studies with G-CSF, GM-CSF, pegylated G-CSF, SCF, and IL-3 are summarized. When and how potassium iodide should be used after exposure to radioiodines is also reviewed. In Section IV, Dr. James Armitage describes a narrow "window" of 7 to 10 Gy where therapy with stem cell transplantation may be appropriate. Victims who are candidates for allotransplantation should not have major trauma or significant injury to other (nonhematopoietic) tissues. Rarely, victims may have an identical sibling or autologous stored marrow or blood stem cells, in which case the threshold for transplantation is 4 Gy. In Section V, Dr. Thomas MacVittie describes new directions for therapy, using cytokines such as IL-7, keratinocyte growth factor, and FLT-3. The potential for combinations of cytokines to enhance hematopoietic recovery is also reviewed.
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7
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Boursalian TE, Bottomly K. Survival of Naive CD4 T Cells: Roles of Restricting Versus Selecting MHC Class II and Cytokine Milieu. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.7.3795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
The diversity of naive CD4 T cells plays an important role in the adaptive immune response by ensuring the capability of responding to novel pathogens. In the past, it has been generally accepted that naive CD4 T cells are intrinsically long-lived; however, there have been studies suggesting some CD4 T cells are short-lived. In this report, we identify two populations of naive CD4 T cells: a long-lived population as well as a short-lived population. In addition, we identify two factors that contribute to the establishment of long-lived naive CD4 T cells. We confirm earlier findings that MHC class II interaction with the TCR on CD4 T cells is important for survival. Furthermore, we find that MHC class II alleles with the correct restriction element for Ag presentation mediate the peripheral survival of naive CD4 T cells more efficiently than other positively selecting alleles, regardless of the selecting MHC in the thymus. The second component contributing to the survival of naive CD4 T cells is contact with the cytokines IL-4 and IL-7. We find that the physiological levels of IL-4 and IL-7 serve to enhance the MHC class II-mediated survival of naive CD4 T cells in vivo.
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Affiliation(s)
- Tamar E. Boursalian
- Section of Immunobiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, CT 06520
| | - Kim Bottomly
- Section of Immunobiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, CT 06520
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8
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Timm JA, Thoman ML. Maturation of CD4+ Lymphocytes in the Aged Microenvironment Results in a Memory-Enriched Population. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.2.711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
With advancing age the CD4+ T lymphocyte compartment becomes enriched for memory cells in both humans and experimental animals. Although it has been assumed that the shift from a naive to a memory-dominant population is due to a lifetime of antigenic exposure and selection as well as a loss of naive cell input due to reduced thymopoiesis, the present data suggest that the aged microenvironment influences the maturation of newly produced CD4+ T cells. In two models, aged and young mice were compared for the ability to reconstitute their peripheral CD4+ T cell pools following depletion, and both age groups were found to be competent to renew this population. However, the phenotype and lymphokine profile of populations arising in aged animals were distinctly different from those in the young mice. In contrast to the expectation that depletion and reconstitution might give rise to a naive-dominant T cell pool, aged mice reconstituted a population nearly indistinguishable from that found in control age-matched individuals. The majority of the CD4+ pool were CD44high CD45RBlow Mel-14low and upon activation with anti-CD3 these CD4+ T cells produced mRNA for IL-2, IL-4, IL-5, and IFN-γ. In aged bone marrow-transplanted mice, the same phenotypic profile and cytokine mRNA pattern were found in CD4+ T cells of host and donor origin. In contrast, the majority of CD4+ T cells in young reconstituted mice were CD44low CD45RBhigh Mel-14high. These lymphocytes, when activated, produced high levels of mRNA for IL-2, with little or no IL-4, IL-5, or IFN-γ mRNA.
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Affiliation(s)
- Jenna A. Timm
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
| | - Marilyn L. Thoman
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
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Boursalian TE, Bottomly K. Stability of Naive and Memory Phenotypes on Resting CD4 T Cells In Vivo. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.1.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
The reliable identification of naive and memory CD4 T cells is critical to understanding the cellular basis of immunological memory. However, it has long been a controversial issue whether naive and memory phenotypes are stable among resting CD4 T cells in the absence of overt stimulation or whether the proposed memory phenotype is a transient, reversible one that represents recently activated cells. In this study, adoptively transferred, purified populations of naive or memory phenotype CD4 T cells are monitored over time to assess the stability of phenotypes and the functional capabilities of transferred cells. Studying both TCR transgenic and nontransgenic CD4 T cell populations allows one to control for the capacity to respond to environmental Ags in vivo. Several findings are reported. The first is that in the absence of Ag, both naive and memory phenotypes remain unchanged over time. Second, when changes are seen in populations of transferred naive phenotype CD4 T cells, they take place only when there is a potential for antigenic challenge, suggesting that it is an Ag-driven event. Furthermore, when a change from naive to memory phenotype is observed, these transferred donor cells also function as memory cells. Third, the ability of memory CD4 T cells to retain the memory phenotype is independent of specific Ag.
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Affiliation(s)
- Tamar E. Boursalian
- Section of Immunobiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, CT 06511
| | - Kim Bottomly
- Section of Immunobiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, CT 06511
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Ramanathan S, Norwich K, Poussier P. Antigen Activation Rescues Recent Thymic Emigrants from Programmed Cell Death in the BB Rat. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.12.5757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
One of the diabetes susceptibility genes of the BB rat is a mutation at the lyp locus that decreases the thymic output of T cells and the life span of most recent thymic emigrants (RTE). Consequently, there is a 10-fold reduction in the number of CD4+ and CD8+ T cells in secondary lymphoid organs. Results presented in this work demonstrate that the BB rat lyp mutation is associated with an accelerated apoptotic death in vitro of mature CD4+8− and CD4−8+ thymocytes and peripheral T cells. The stability of the pool of recirculating T cells (PRL) of BB rats over time results from a >10-fold increase in the mitotic activity of T cells as assessed in vivo by bromodeoxyuridine incorporation. This increased mitotic activity is not observed when BB T cells develop in the context of a normal sized PRL. MHC haploidentical WF and BB rats differ at minor histocompatibility loci. Intravenous injection of (WF × BB)F1 T cells into euthymic BB rats led to the rejection of donor T cells within 3 wk by unprimed recipients and within 1 wk by primed recipients. This secondary immune response was unaffected by postpriming thymectomy. F1 T cells were not rejected, but rather expanded after their injection into thymectomized BB rats that had been primed as early as 48 h after thymectomy. These results strongly suggest that the BB rat PRL is devoid of long-lived naive T cells and that rescue of recent thymic emigrants from programmed cell death is initiated by Ags, exclusively.
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Affiliation(s)
| | - Ken Norwich
- ‡Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
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