Diss. (sammanfattning) Umeå : Umeå universitet, 2010.

Human γδ T cells expressing the Vγ2Vδ2 T cell antigen receptor play important roles in immune responses to microbial pathogens by monitoring prenyl pyrophosphate isoprenoid metabolites. Most adult Vγ2Vδ2 cells are memory cytotoxic cells that produce interferon-γ (IFN-γ). Recently, murine γδ T cells were found to be major sources of interleukin (IL)-17A in anti-microbial and autoimmune responses. To determine if primate γδ T cells play similar roles, we characterized IL-17A and IL-22 production by Vγ2Vδ2 T cells. IL-17A-producing memory Vγ2Vδ2 T cells exist at low but significant frequencies in adult humans (1:2,762 T cells) and at even higher frequencies in adult rhesus macaques. Higher levels of Vγ2Vδ2 T cells produce IL-22 (1:1,864 T cells) although few produce both IL-17A and IL-22. Unlike adult humans where many IL-17A+ V#947;2Vδ2 T cells also produce IFN-#947; (T#947;δ1/17), the majority of adult macaques IL-17A+ Vδ2 T cells (T#947;δ17) do not produce IFN-#947;. To define the cytokine requirements for T#947;δ17 cells, we stimulated human neonatal V#947;2Vδ2 T cells with the bacterial antigen, (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate, and various cytokines and mAbs in vitro. We find that IL-6, IL-1β, and transforming growth factor-β (TGF-β) are required to generate T#947;δ17 cells in neonates whereas T#947;δ1/17 cells additionally required IL-23. In adults, memory T#947;δ1/17 and T#947;δ17 cells required IL-23, IL-1β, and TGF-β but not IL-6. IL-22-producing cells showed similar requirements. Both neonatal and adult IL-17A+ V#947;2Vδ2 T cells expressed elevated levels of retinoid-related orphan receptor-#947;t. Our data suggest that, like Th17 αβ T cells, V#947;2Vδ2 T cells can be polarized into T#947;δ17 and T#947;δ1/17 populations with distinct cytokine requirements for their initial polarization and later maintenance.

The peripheral naive CD4 T cell pool is homeostatically regulated through a balance of thymic production, delivery of survival signals and homeostatic proliferation. CD4 recent thymic emigrants (RTEs) have a high T cell receptor excision circle (TREC) content and express high levels of CD31. We report premature thymic involution in RRMS, initiated by reduced numbers of naive CD4 T cells and various naive CD4 T cell subsets in peripheral blood. Further, CXCR4, a receptor involved in emigration from the thymus, and CD127 and Bcl-2 (survival signals) are upregulated in various naive CD4 T cell subsets in RRMS. As a compensatory process, naive CD4 T cells undergo homeostatic proliferation. This proliferation is a form of peripheral positive selection through self-MHC/self-antigen interaction and thus can contribute to the expansion of autoreactive T cells and predispose to development of RRMS.

The immune system generates discrete lineages of cells that are designed to respond optimally to environmental cues and infectious agents. Two distinct lineages of T cells, distinguished by expression of either an αβ or γδ T cell receptor (TCR), arise from a common progenitor in the thymus. The type of pathogen and the cytokine milieu directs effector differentiation of αβ T cells in the periphery through the induction of specific transcriptional networks. γδ T cell development is distinct from that of αβ T cells in its ordered rearrangement of TCR genes and the pairing of Vγ and Vδ chains to generate γδ T cell subsets that home to specific tissues. Unlike conventional αβ T cells, γδ T cells express a preactivated or memory phenotype prior to pathogen encounter, and recent evidence indicates that effector functions may be programmed during thymic development. To better understand the development and function of γδ T cells, we analyzed the gene expression profiles of subsets of γδ T cells segregated by TCR repertoire and maturation state in the thymus. We also determined the impact of TCR signaling and trans-conditioning on γδ T cell subset-specific gene signatures by analysis of Itk-/- and Tcrb-/- γδ T cell subsets. Our analysis has defined three stages of γδ T cell subset-specific differentiation, and indicates that γδ T cells may consist of at least two separate lineages, distinguished by the expression of a Vγ2 or Vγ1.1 TCR, that arise from different precursors during thymic development. Key transcriptional networks are established in immature γδ T cells during the first phase of development, independent of TCR signaling and trans-conditioning, with Vγ2+ cells expressing modulators of WNT signaling, and Vγ1.1+ cells expressing high levels of inhibitor of DNA binding 3 (ID3), which regulates E2A/HEB proteins. The second stage involves the further specification of the Vγ2+ subset specific gene signature, which is dependent upon ITK-mediated signals. In the third stage, terminal maturation of γδ T cell subsets occurs, dependent on both TCR and trans-conditioning signals. The expression patterns of Vγ1.1+ subsets that differ in Vδ usage diverge, and all subsets further elaborate and reinforce their effector programming by the distinct expression of chemokine and cytokine receptors. Alteration of WNT signaling or E2A/HEB activity results in subset specific defects in effector programming, indicating that the transcriptional networks established at the immature stage are crucial for the functional maturation of γδ T cells. These data provide a new picture of γδ T cell development, regulated by multiple checkpoints that shape the acquisition of subset-specific molecular signatures and effector functions.

No description available.

This dissertation addresses the role for Janus Kinase 3 (Jak3) in CD4+ T cell homeostasis and function. Jak3 is a protein tyrosine kinase whose activity is essential for signals mediated by the γc dependent cytokines IL-2, -4, -7, -9, -15, and -21. Previous data have demonstrated that peripheral CD4+ T cells from Jak3-deficient mice have a memory phenotype and are functionally impaired in both proliferative and IL-2 responses in vitro. Interestingly, Jak3/γc activity has been previously shown to play a role in the prevention of T cell anergy. These studies were initiated to more precisely define the role for Jak3/γc cytokines in the prevention of T cell anergy and the maintenance of functional CD4+ T cell responses. We began to address this question by assessing global gene expression changes between wild type and Jak3-/- CD4+ T cells. These data indicate that Jak3-/- CD4+ T cells have an increase in gene expression levels of inhibitory surface receptors as well as immunosuppressive cytokines. Further analyses confirmed that Jak3-deficient T cells express high levels of PD-1, secrete a Trl-type cytokine profile following direct ex vivo activation, and suppress the proliferation of wild type T cells in vitro. These characteristics indicate that CD4+ Jak3-/- T cells share properties with regulatory T cell subsets that have an important role in peripheral tolerance and the prevention of autoimmunity. We next addressed whether these regulatory characteristics were T cell intrinsic or rather the result of expanding in a Jak3-deficient microenvironment characterized by a number of immune abnormalities and a disrupted splenic architecture. Jak3-/- CD4+ T cells proliferate in vivoin a lymphopenic environment and selectively acquire regulatory T cell characteristics in the absence of any additional activation signals. While the precise mechanism by which Jak3-deficient T cells acquire these characteristics remains unclear, our data indicate that one important component is a T cell-intrinsic requirement for Jak3 signaling. These findings indicate several interesting aspects of T cell biology. First, these studies, demonstrate that the homeostatic proliferation of CD4+ T cells is not dependent on signaling via γc-dependent cytokine receptors. And, second, that the weak activation signals normally associated with homeostatic expansion are sufficient to drive Jak3-/- T cells into a non-conventional differentiation program. Previous data indicate that, for wild type T cells, signaling through both the TCR as well as γc-dependent cytokine receptors promote the homeostatic proliferation of T cells in lymphopenic hosts. Since Jak3-/- T cells are unable to receive these cytokine signals, their proliferation is likely to be wholly dependent on TCR signaling. As a consequence of this TCR signaling, Jak3-/- T cells proliferate, but in addition, are induced to up regulate PD-1 and to selectively activate the IL-10 locus while shutting off the production of IL-2. Since this fate does not occur for wild type T cells in a comparable environment, it is likely that the unique differentiation pathway taken by Jak3-/- T cells reflects the effects of TCR signaling in the absence of γc-dependent cytokine signaling. Interestingly, wild type T cells undergoing homeostatic expansion in lymphopenic hosts show many common patterns of gene expression to freshly-purified unmanipulated Jak3-/- T cells. For instance, micro array analysis of gene expression in wild type CD4+ T cells after lymphopenia induced homeostatic expansion show a similar pattern of upregulation in surface markers (PD-1 and LAG-3), and cytokine signaling molecules (IL-10 and IFN-γ cytokine, receptors, and inducible gene targets) to that of Jak3-/- CD4+ T cells immediately ex vivo. These data suggest that the process of homeostatic proliferation normally induces immune attenuation and peripheral tolerance mechanisms, but that full differentiation into a regulatory T cell phenotype is prevented by γc-dependent cytokine signals. Taken together these data suggest that Jak3 plays an important role in tempering typical immune attenuation mechanisms employed to maintain T cell homeostasis and peripheral tolerance.

Σκοπός. Η διαβητική κετοξέωση (ΔΚ) και η υπεργλυκαιμική υπερωσμωτική κατάσταση (ΥΥΚ) είναι δύο από τις πιο σοβαρές οξείες επιπλοκές του Σακχαρώδη διαβήτη, που εξακολουθούν να αποτελούν σημαντική αιτία νοσηρότητας και θνητότητας μεταξύ των διαβητικών. Οι λοιμώξεις, συχνός εκλυτικός παράγων και επιπλοκή της ΔΚ και ΥΥΚ, αποτελούν την κύρια αιτία θανάτου και η έγκαιρη διάγνωση και αντιμετώπιση της σήψης είναι κριτικής σημασίας για την επιβίωση των ασθενών. Διερευνήσαμε την επίδραση των ανωτέρω καταστάσεων στην ανοσοποιητική απόκριση, μελετώντας τους υποπληθυσμούς των Τ λεμφοκυττάρων – παραμέτρους οξείας φάσης και την ιντερλευκίνη 6 (IL-6) στο περιφερικό αίμα των ασθενών μας, σε μια προσπάθεια να διαπιστώσουμε τυχόν υποκείμενες διαταραχές και να προσδιορίσουμε πιθανόν διαγνωστικούς και προγνωστικούς δείκτες για τη σήψη. Μέθοδος. Η μελέτη μας περιέλαβε 61 διαβητικούς ασθενείς με ΔΚ ή ΥΥΚ. Ξεχωρίσαμε μια ομάδα ασθενών που είχαν συμπτώματα Συνδρόμου συστηματικής φλεγμονώδους αντίδρασης (SIRS). Προσδιορίσαμε στον ορό όλων των ασθενών τις συγκεντρώσεις των παραγόντων οξείας φάσης (συμπεριλαμβανομένης της C αντιδρώσας πρωτεΐνης ,CRP) και της IL-6 (ως κύρια κυτταροκίνη για την παραγωγή πρωτεϊνών οξείας φάσης), κατά την εισαγωγή και στην ύφεση (μετά τη βελτίωση των συμπτωμάτων και σε κατάσταση ευγλυκαιμίας). Σε μια ομάδα 28 ασθενών με ΔΚ ή ΥΥΚ (σε σύγκριση και με αντίστοιχη ομάδα ελέγχου) μελετήσαμε επιπλέον υποπληθυσμούς των Τ λεμφοκυττάρων, τα ολικά (CD3) / τα βοηθητικά (CD4) / τα κατασταλτικά (CD8) Τ κύτταρα και τα κύτταρα φυσικοί φονείς (ΝΚ) χρησιμοποιώντας μονοκλωνικά αντισώματα και μικροσκόπιο ανοσοφθορισμού, προ και αμέσως μετά τη διόρθωση της μεταβολικής διαταραχής. Αποτελέσματα. Παρατηρήσαμε ότι οι υποπληθυσμοί των Τ λεμφοκυττάρων ήταν σημαντικά ελαττωμένοι κατά την εισαγωγή, συγκρινόμενοι με τους υγιείς μάρτυρες (ενώ οι περισσότερες μελέτες διαβητικών τύπου 1 καταγράφουν αυξημένα βοηθητικά Τ κύτταρα) και παρέμειναν και αμέσως μετά τη διόρθωση της μεταβολικής διαταραχής. Οι ασθενείς που τελικά απεβίωσαν είχαν σημαντικά ελαττωμένους τους υποπληθυσμούς των Τ λεμφοκυττάρων (εκτός των ΝΚ κυττάρων) συγκρινόμενοι και με τους υγιείς μάρτυρες και με όσους ασθενείς επιβίωσαν. Από τους 61 ασθενείς της μελέτης με ΔΚ ή ΥΥΚ, οι 49 ασθενείς είχαν συμπτώματα SIRS. Οι 27 ασθενείς είχαν SIRS χωρίς στοιχεία λοίμωξης, ενώ οι 22 ασθενείς είχαν SIRS με αποδεδειγμένη λοίμωξη. Διαπιστώσαμε σημαντικά αυξημένες συγκεντρώσεις CRP και IL-6 στον ορό των σηπτικών διαβητικών ασθενών συγκριτικά με όσους ασθενείς μας είχαν SIRS χωρίς λοίμωξη. Οι ασθενείς που τελικά απεβίωσαν είχαν σημαντικά πιο αυξημένες συγκεντρώσεις CRP και IL-6 κατά την εισαγωγή, που μειώθηκαν σημαντικά στην ύφεση. Συμπεράσματα. Η διαβητική κετοξέωση και η υπεργλυκαιμική υπερωσμωτική κατάσταση προκαλούν συχνά κλινικό σύνδρομο που ομοιάζει με σύνδρομο συστηματικής φλεγμονώδους αντίδρασης. Διαταραχές στην ισορροπία των υποπληθυσμών των Τ λεμφοκυττάρων, κυρίως η ελάττωση των βοηθητικών Τ κυττάρων μπορεί να συμβάλλουν στην υψηλή θνησιμότητα αυτών των μεταβολικών διαταραχών. Οι μετρήσεις των συγκεντρώσεων C αντιδρώσας πρωτεΐνης και ιντερλευκίνης 6 στον ορό αυτής της ομάδας των διαβητικών ασθενών, είναι ένας χρήσιμος τρόπος αποκλεισμού λοίμωξης και επιβεβαίωσης και παρακολούθησης της σήψης. / Aims / hypothesis. Diabetic ketoacidosis (DKA) and hyperglycemic hyperosmolar state (HHS) are two of the most serious acute complications of diabetes mellitus, being important causes of morbidity and mortality among patients with diabetes. Infection is a common precipitating event in DKA and HHS and the major cause of death. An early diagnosis of sepsis in patients with DKA and HHS is crucial and life saving. We studied the immune responses in these states, investigating the peripheral T lymphocyte subsets, acute phase reactants and interleukin 6 (IL-6) to find out how useful these might be for identifying sepsis. Methods. Sixty one diabetic patients with DKA or HHS were enrolled. Patients with signs and symptoms of systemic inflammatory response syndrome (SIRS) were identified. Acute phase reactants, including serum C-reactive protein (CRP) and IL-6, the main cytokine responsible for the induction of acute phase proteins, were measured (concentrations in peripheral blood) on admission and when patients were clinically improved and were euglycaemic. Peripheral T lymphocyte subsets including total (CD3), helper (CD4) and suppressor (CD8) T cells and natural killer (NK) cells, were studied in twenty one patients with DKA plus seven patients with HHS and twenty eight healthy matched control (using monoclonal antibodies), prior to and after treatment of metabolic disorders. Results. Peripheral T lymphocyte subsets were decreased in the twenty eight patients with DKA and HHS in admission compared to healthy controls (while helper T cells are mostly increased in diabetics type 1), and remained so after treatment of metabolic disorders. Patients who finally died had significantly decreased T lymphocyte subsets (except NK cells) compared with both healthy controls and patients who survived. A total of forty nine out of sixty one patients with DKA and HHS had signs of SIRS. Twenty seven patients had SIRS and no signs of infection and twenty two patients had SIRS due to proven infection. We detected a significant increase in serum CRP and IL-6 values in patients infected compared to patients with no septic SIRS. Patients who finally died had much higher levels of these proteins, while there was a prompt reduction of serum CRP and IL-6 early during remission. Conclusion / interpretation. Diabetic ketoacidosis and hyperglycemic hyperosmolar state can often cause a clinical syndrome resembling systemic inflammatory response syndrome. An imbalance of subpopulations of T lymphocytes, especially decreased helper T cells (CD4), may be correlated with the high morbidity and mortality in these states. Determination of serum C-reactive protein and interleukin-6 is a useful way of early excluding an underlying infection as well as confirming and monitoring sepsis.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 122-140.

Previously, our lab demonstrated that heterologous immunity could result in either gain or loss of protective immunity and alteration in immune pathology following infection by a second un-related pathogen. One of the prototypical models to study T cell-mediated heterologous immunity involves two distantly related arenaviruses, namely lymphocytic choriomeningitis virus (LCMV) and Pichinde virus (PV). Each virus encodes a cross-reactive CD8 epitope that has six out of eight in amino acid (aa) similarity with respect to its counterpart at the position 205-212 of the nucleoprotein (NP205). Heterologous challenge between LCMV and PV results in 1) expansion of the cross-reactive NP205-specific CD8 T cell responses and alteration of the immunodominance hierarchy and 2) partial protective immunity (heterologous immunity). Our lab showed that cross-reactive NP205-specific CD8 T cell receptor (TCR) repertoires become extremely narrowed following a heterologous challenge between LCMV and PV. Therefore, I questioned if LCMV NP205 epitope escape variants could be isolated during a dominant but narrowed crossVI reactive NP205-specific CTL response. In the first part of my thesis, I describe the isolation of a LCMV NP-V207A CTL escape variant in vivo using PV-immune animals challenged with LCMV clone 13. The LCMV NP-V207A variant contains a point mutation, which results in the switching of valine to alanine at the third non-anchoring residue of the LCMV NP205 CD8 epitope. Immunization of mice with the LCMV NP-V207A variant results in a significantly diminished cross-reactive NP205-specific CD8 T cell response. This suggests that the point mutation is responsible for the loss in the immunogenicity of the LCMV NP205 CD8 epitope. In addition, an in vitrorescued(r) recombinant LCMV variant (r/V207A) that encodes the original mutation also induces a highly diminished cross-reactive NP205-specific CD8 T cell response in mice. In agreement with the result obtained from the intracellular cytokine assays (ICS), MHC-Ig dimers loaded with the LCMV NP205 (V-A) peptide could only detect a minute population of cross-reactive NP205-specific CD8 T cells in mice infected with r/V207A variant virus. All the data indicate that the point mutation results in a significant loss in immunogenicity of the LCMV NP205 CD8 epitope. So far, no direct link between the cross-reactive NP205-specific CD8 T cells and heterologous immunity had been established in this system. Therefore, we immunized mice with either LCMV WT or the LCMV NP-V207A variant virus and showed that a significant loss of heterologous immunity is associated with the group immunized with LCMV NP-V207A variant virus. Again, r/V207Aimmune animals also displayed a significant loss in heterologous immunity following PV challenge. This suggests that the cross-reactive NP205-specific CD8 T cells mediate the majority of heterologous immunity between LCMV and PV in vivo. In comparison to the PV-immune control group, PV clearance kinetics mediated by the cross-reactive NP205-specific CD8 T cells were significantly delayed. Finally, these data also suggest that bystander activation plays very little role in heterologous immunity between LCMV and PV. Many studies in murine systems and humans suggest that cross-reactive T cells are often associated with immune pathology. We showed that in mice that were sequentially immunized with PV and LCMV (PV+LCMV WT double immune mice), there was a development of a high incidence and high level of immune pathology known as acute fatty necrosis (AFN) following a final PV challenge. The data suggest that these cross-reactive NP205-specific CD8 T cells might play an important role in immune pathogenesis. Therefore, we asked if the cross-reactive NP205-specific CD8 T cells play a role in immune pathogenesis by comparing the incidence of AFN between the (PV+LCMV WT) and the (PV+LCMV NP-V207A) double immune mice following a final PV challenge. In agreement with our hypothesis, the result showed the (PV+LCMV NP-V207A) double immune mice developed a significantly lower incidence of AFN compared to the (PV+LCMV WT) double immune mice. However, linear correlation studies comparing the frequency of different antigen-specific CD8 T cell populations within the (PV+LCMV WT) double immune mice before challenge and the severity of AFN following the PV challenge suggest that two opposing antigen-specific CD8 T cell populations are involved in determining the final outcome of the immune pathology. The PV NP38-45-specific CD8 T cell response (PV NP38) appears to be more protective than the cross-reactive NP205-specific CD8 T cell response. In addition, a positive linear correlation between the ratio of cross-reactive NP205 to PV NP38 and the severity of AFN seem to suggest that these cross-reactive populations are important contributors to immune pathogenesis. Peptide titration studies examining the functional avidities to different antigenic specificities suggest that both populations consist of high avidity TCR and peptide MHC (TCR:pMHC) interactions. However, skewing within the cross-reactive NP205 specific CD8 T cell response towards the LCMV NP205 epitope response in one of the (PV+LCMV WT) double immune mice suggests that cross-reactive NP205 specific CD8 T cells could constitute a sub-optimal response to a PV challenge. In summary, I questioned what might be some of the immunological consequences of heterologous immunity in this model. First of all, we have established a direct link between the cross-reactive NP205-specific CD8 T cell response and heterologous immunity in LCMV and PV. Second of all, I demonstrated that a LCMV NP205 epitope escape variant could be selected in vivo under the conditions of heterologous immunity. In addition, I showed that PV clearance kinetic was significantly delayed in cross-reactive NP205-mediated heterologous immunity as compared to homologous challenge. Finally, we demonstrated that cross-reactive NP205-specific CD8 T cells could play an important role in immune pathogenesis in this model. However, correlation data indicate that two opposing antigen-specific CD8 T cell populations could ultimately decide the outcome and magnitude of immune pathology in each individual mouse. All the data presented above strongly suggest that the cross-reactive NP205 CD8 T cells play a crucial role in immune pathology in this model system by 1) interfering with the regular establishment of immunodominance hierarchy orders, or 2) exhibiting a sub-optimal protective immunity due to the nature of the cross-reactive epitope.