Browsing by Subject "CD8 T cell"

Now showing 1 - 5 of 5
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    Derivation, maintenance, and functions of virtual memory cells.
    (2011-09) Akue, Adovi Dodji
    Memory phenotype CD8+ T cells are typically thought to have undergone an immune response to foreign antigen and to have differentiated from antigen-specific precursors in the naïve pool. However, using a peptide-MHC I tetramer enrichment technique, we identified foreign antigen-specific memory-phenotype CD8+ T cells in unimmunized mice. These cells (termed "virtual memory" T or VM cells) were observed in mice maintained in both specific-pathogen- and germ-free (SPF and GF respectively) housing. This thesis focuses on the relationship between VM cells and "conventional" memory cells: memory cells arising from homeostatic proliferation (HP), and innate-like memory CD8+ T cells such as IL-4 bystander memory CD8+ T cells. Our data indicate physiological HP and IL-4-driven bystander processes are the main mechanisms that drive the generation of VM cells and not the exposure to foreign antigens. VM cells arise in the periphery during the neonatal period and are maintained long term. We also show that VM cells respond in vitro to innate cytokines (similar to conventional memory CD8+ T cells) and they outcompete antigen-specific naive CD8+ T cells in in vivo responses. Overall our observations suggest that VM cells arise out of normal homeostatic and IL-4-driven bystander processes in unimmunized SPF and GF mice, and express at least some memory-like capabilities.
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    Essential discrimination of vascular and tissue lymphocytes redefines CD8 T cell responses to respiratory infection
    (2014-03) Anderson, Kristin Gail
    Characterizing the cellular participants in tissue immune responses is critical for understanding infection, cancer, autoimmunity, allergy, graft rejection, and other immunological processes. Leukocytes recirculate through blood vessels before localizing to tissue sites of immune responses. Thus, in experimental animal models, tissues are often perfused to putatively remove blood-borne leukocytes that may conflate analysis. Here, we develop and validate an intravascular staining methodology that distinguishes between vascular and tissue-localized cells of the immune system. We demonstrate that perfusion both fails to remove many blood-borne leukocytes and also may remove tissue-localized populations of interest, and we provide examples of how this issue distorts interpretation of leukocyte differentiation state, migration, and phenotype in healthy mice, as well as those responding to viral or Mycobacterium tuberculosis infection or tumor challenge. Additionally, we utilize intravascular staining to examine resident memory T cells in non-lymphoid tissues, such as the lung, liver and female reproductive tract. This study highlights the breadth and gravity of the issues regarding tissue leukocyte composition, outlines simple methods for identification of various intravascular leukocyte populations, reviews the limitations of the technology, and demonstrates that these methods should be routinely adopted in lieu of perfusion for interpretable and accurate analyses of immune responses in many tissues.
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    Evaluating memory CD8 T cell quantity, distribution and migration
    (2016-08) Steinert, Elizabeth
    Memory CD8 T cells protect against intracellular pathogens by scanning host cell surfaces, thus infection detection rates depend on memory cell number and distribution. Many cell population analyses rely on isolation from whole organs and interpretation is predicated on presumptions of near-complete cell recovery. Paradigmatically, T cell memory is parsed into central, effector, and resident subsets, ostensibly defined by immunosurveillance patterns, but in practice identified by phenotypic markers. Because isolation methods and subsequent phenotypic marker-based analyses ultimately inform models of memory T cell differentiation, protection, and vaccine translation, we tested their validity via quantitative immunofluorescence microscopy of a murine memory CD8 T cell population. We found that lymphocyte isolation fails to recover most cells and recovery is biased against certain subsets. Applying this approach to parabiotic mice we found that the overwhelming majority of memory CD8 T cells in non-lymphoid tissues are resident, rather than recirculating. Residence was not absolutely predicted by common phenotypic markers (CD103 & CD69), a finding that demonstrates heterogeneity in the resident memory population and insists that migration rather than solely phenotype be used for identification. Despite tissue-specific immune regulation, establishment of resident memory CD8 T cells was extended to male genital tract tissues, where they maintain local cytokine production in the presence of rechallenge. Our studies of male genital tract organs revealed non-canonical migration of effector CD8 T cells directly into visceral non-lymphoid tissues of recently infected mice. Together, these results provide a systematic quantification of the distribution and compartmentalization of virus-specific memory CD8 T cell subsets and highlight the relative numerical abundance of resident memory CD8 T cells, indicating that host immunosurveillance by memory CD8 T cells is conducted in a highly localized manner.
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    Immune Modulation of Adult Neurogenesis during Experimental Herpes Simplex Encephalitis
    (2015-05) Rotschafer, Jessica
    Herpes Simplex Virus-1 (HSV-1) is the primary cause of sporadic viral encephalitis in the United States. While prompt treatment results in high survival rates, greater than fifty percent of patients develop severe, life-altering neurological deficits subsequent to Herpes Simplex encephalitis (HSE). Inflammatory cues generated during non-HSE viral encephalitis have been shown to alter reparative neurogenesis in humans and mice. However, interactions between induced immune responses and the normal processes of adult neurogenesis remain unexplored during HSE. The present thesis hypothesized that inflammation induced by experimental HSV-1 infection of laboratory mice alters neural stem/progenitor cell (NSC) proliferation. The response of NSCs was dynamic throughout HSV-1 infection of adult BALB/c mice, with a significant increase in the NSC population during acute HSE at 6 d p.i. and a significant decrease by 15 d p.i.. The 6 d p.i. and 15 d p.i. time points coincided with macrophage infiltration and CD8(+) T cell infiltration respectively. At 6 d p.i., infiltrating macrophages were observed to be alternatively activated (M2) whereas macrophages at 15 d p.i. were classically activated (M1 macrophages). Treatment with M2 macrophages resulted in significant increases in the NSC population size both in vivo and in vitro. In vitro, the increase in NSC proliferation was found to be mediated via Wnt5a. In vivo, transplanted M2 macrophages increased the number of NSCs and Wnt5a(+)CD11b(+) macrophages were observed in the brains of 5 d p.i. mice. On the other hand, M1 macrophages activated with interferon-γ did not support NSC proliferation, which suggested that macrophage effects may be modulated by other immune factors present in the infected brain. CD8(+) T cells are the largest population of infiltrating immune cells during chronic HSE and produce robust amounts of IFN-�. The interactions of CD8(+) T cells and NSCs were addressed in vitro and in vivo experiments. Co-culture of activated CD8(+) T cells and NSCs abrogated NSC proliferation in vitro while in vivo depletion of CD8(+) T cells restored the NSC population in infected mice. Further evaluation of the effect of CD8(+) T cells on NSC proliferation was dependent on IFN-� both in vivo and in vitro, as IFN-� receptor 1 (IFN-�R1) knockout mice were unresponsive to CD8(+) T cells in culture and infected IFN-�R1 knockout mice had no reduction in the size of the NSC population. To continue evaluation of interactions of NSC proliferation and IFN-�, alternative models of HSE were assessed in C57BL/6 mice. The kinetics of immune cell and NSC proliferation were similar between BALB/c and C57BL/6 mice, but macrophage and T cell phenotypes were different between the strains. Macrophages infiltrating the brain, at any time point examined, were persistently classically activated with an M1 phenotype, and T cell infiltration was dominated by CD4(+) T cells in C57BL/6 mice. On the other hand, NSC proliferation was significantly decreased when IFN-� was expressed suggesting that the interactions of IFN-� and NSCs were similar in both strains of mice tested. The studies presented in this dissertation are the first to suggest a connection between IFN-� produced by infiltrating T cells and impaired NSC proliferation. The mechanism by which T cells mediate this effect may be direct or through interaction with other cell types in the brain. However, there are implications that NSC proliferation and associated reparative neurogenesis may be impacted in any model of brain damage that exhibits prominent IFN-� expression.
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    Immunological responses during the incubation period and acute phase of naturally acquired primary Epstein-Barr virus infection
    (2015-07) Dunmire, Samantha
    Epstein-Barr virus (EBV) in a human herpesvirus. It infects about 90% of the human population, and is the main causative agent of infectious mononucleosis. The incubation period, the time between viral acquisition and onset of symptoms, is unusually long in patients presenting with infectious mononucleosis, lasting about six weeks. In addition to causing acute illness, there can also be long-term consequences as the result of acquisition of the virus, including nasopharyngeal carcinoma and lymphoma. Nevertheless, there remains a surprising dearth of knowledge regarding the establishment of and immune response to persistent EBV infection in its natural hosts, especially during the incubation period. We sought to address many of these gaps by studying the incubation period, acute phase, and convalescence of undergraduates experiencing infectious mononucleosis during primary natural EBV infection in a cohort of prospectively studied volunteers. Particular attention was paid to the previously uncharacterized incubation period. Our findings have focused on understanding the immune response that occurs in young adults presenting with infectious mononucleosis, via gene expression changes as observed in peripheral blood mononuclear cells and innate and adaptive immune cells. Using a systems biology approach we discovered that important gene expression changes occur during the immune response to primary EBV infection. A typical antiviral type I interferon response was not observed at onset of infectious mononucleosis symptoms, but rather up to two weeks prior. The gene expression signature at symptom onset was dominated by cell cycle related genes, probably due to the CD8 T cell lymphocytosis, and type II interferon regulated genes. Interestingly, comparison of the EBV signature with other acute viral infections revealed very little similarity. The EBV signature showed the greatest similarity with hemophagocytic syndromes. This result is consistent with the view that infectious mononucleosis is an immunopathologic disease, and is supported by evidence that EBV can cause hemophagocytic lymphohistiocytosis. As an extension of this work, we carefully examined changes in cellular phenotypes and population frequencies to determine if there were significant alterations to certain compartments during the response to primary EBV infection. We observed a type I interferon signature in a larger subset of study participants during the incubation period. This response was concurrent with the transition of virally infected B cells from the oral cavity to the blood, a decline in plasmacytoid dendritic cells from the circulation, and a polyclonal CD8 T cell activation. No EBV specific CD8 T cells activation was observed until the onset of infectious mononucleosis symptoms. A major obstacle to understanding EBV related sequelae has been the lack of an efficient animal model for EBV infection, although progress in primate and mouse models has recently been made. Taken together, the data compiled in this thesis provide important first descriptions of the immune responses that occur during the establishment of a natural persistent infection in humans. Key future challenges are to develop protective vaccines and effective treatment regimens.