Repeated Antigen Exposure Research Articles

Mechanisms of failure of chimeric antigen receptor T-cell therapy.

Although chimeric antigen receptor T (CART)-cell therapy is best recognized for its antitumor effect in relapsed/refractory B-cell hematological cancers, it is still associated with a high relapse rate. We firstly analyzed internal immunological and genetic reasons of CD19+ relapse after treatment for R/R B-cell hematological cancers with CART19 cells. The reasons: murine-derived scFv may limit expansion of CART cells. Repeated antigen exposure leads to T-cell exhaustion. Activation of T cells can cause T-cell senescence and high expression of inhibitive receptors, PD-1, CTLA4, TIGIT, LAG-3, CD244, CD160, TIM3, which might be solved by some external pharmacological intervention methods [for instance, the use of FC (Fludarabine, Cyclophosphamide) lymphodepletion regimen, lenalidomide, PD-1 inhibitor, ibrutinib and humanized CD19-CART cells. Secondly, mechanism of CD19 relapse can be attributed to the preexisting of CD19 subclone, the loss or alternative RNA splicing on exon 2 of chromosome 16 on which CD19 gene is located, B-cell transcript factors - paired-box 5 (PAX5) and early B-cell factor 1 (EBF1) are down-regulated to cause lineage-switch from lymphoid to myeloid. Although different preparation techniques generates various entities of CART 19 cells, these problems could be conquered by novel agents and novel CAR system. Although Chimeric Antigen Receptor T (CART) cell therapy is best recognized for its antitumor effect in Relapsed/Refractory B-cell hematological cancers, it still shows a high relapse rate. We review mechanisms of failure of CART therapy. http://links.lww.com/COH/A18.

Lung-draining lymph-node-resident memory CD8 T cells mediate local protective immunity

Abstract Recent studies indicate tissue-resident memory CD8 T cells (Trms) form at both the sites of initial infection and in lymphoid tissues upon resolution of systemic or localized viral infections. We examined if lymph node Trms were also generated in lung-draining mediastinal lymph nodes (mLN) during intranasal infections. Both transgenic P14 cells and endogenous influenza-specific CD69+/CD103+ Trms were detected in lung-draining mLN but absent in non-draining LNs after intranasal infection with recombinant influenza or vaccinia viruses. Similar to lung Trms, which wane over time, these primary memory (1M) mLN Trms had limited persistence with continual contraction throughout the memory phase. As influenza is a seasonal virus, and we previously observed that repeated antigen exposure extended the durability of lung Trms, we investigated the effects of multiple antigen exposures on the mLN Trm population. Similar to their lung Trm-counterparts, the lung-draining LN Trms derived from repeatedly stimulated (4M) memory CD8 T cells exhibited extended survival, down-regulation of Eomesodermin and the shared IL-2/15Rβ CD122 compared to 1M LN Trms. During parabiosis, both 1M and 4M mLN Trms largely maintained residence within their respective hosts. Importantly, hosts containing 4M P14 mLN Trms provided superior early protection against LCMV challenge in the mLN compared to 1M hosts, demonstrating the functional capacity for mLN Trms to contribute to protective anti-viral immune responses. Overall, these data indicate that lung-draining lymph node Trms co-express CD69 and CD103, largely maintain LN-tissue residency and can contribute to subsequent viral infections.

Teaching baby B cells

Adaptive Immunity Antibodies are central to immune defense. B cells can generate several antibody isotypes that fulfill different functional roles, and repeated antigen exposure induces antibody somatic hypermutation. Nielsen et al. studied a longitudinal birth cohort to determine how antigen exposure early in life affects human antibody production. Somatic hypermutation increased as the children got older, and certain VH genes were associated with different isotypes. Increased pathogen exposure was associated with immunoglobulin D (IgD) and IgM mutations. Interestingly, children with eczema or allergies had higher rates of IgE mutation. These valuable data shed light on how human B cells grow up. Sci. Transl. Med. 11 , eaat2004 (2019).

Improved multilineage human hematopoietic reconstitution and function in NSGS mice.

Genetic manipulation of NOD/SCID (NS) mice has yielded numerous sub-strains with specific traits useful for the study of human hematopoietic xenografts, each with unique characteristics. Here, we have compared the engraftment and output of umbilical cord blood (UCB) CD34+ cells in four immune-deficient strains: NS, NS with additional IL2RG knockout (NSG), NS with transgenic expression of human myeloid promoting cytokines SCF, GM-CSF, and IL-3 (NSS), and NS with both IL2RG knockout and transgenic cytokine expression (NSGS). Overall engraftment of human hematopoietic cells was highest in the IL2RG knockout strains (NSG and NSGS), while myeloid cell output was notably enhanced in the two strains with transgenic cytokine expression (NSS and NSGS). In further comparisons of NSG and NSGS mice, several additional differences were noted. NSGS mice were found to have a more rapid reconstitution of T cells, improved B cell differentiation, increased levels of NK cells, reduced platelets, and reduced maintenance of primitive CD34+ cells in the bone marrow. NSGS were superior hosts for secondary engraftment and both strains were equally suitable for experiments of graft versus host disease. Increased levels of human cytokines as well as human IgG and IgM were detected in the serum of humanized NSGS mice. Furthermore, immunization of humanized NSGS mice provided evidence of a functional response to repeated antigen exposure, implying a more complete hematopoietic graft was generated in these mice. These results highlight the important role that myeloid cells and myeloid-supportive cytokines play in the formation of a more functional xenograft immune system in humanized mice.

Repeated Antigen Exposure Extends the Durability of Influenza-Specific Lung-Resident Memory CD8+ T Cells and Heterosubtypic Immunity

Lung-resident primary memory CD8+ Tcell populations (Trm) induced by a single influenza infection decline within months, rendering the host susceptible to new heterosubtypic influenza infections. Here, we demonstrate that, relative to single virus exposure, repeated antigen exposure dramatically alters the dynamics of influenza-specific lung Trm populations. Lung Trm derived from repeatedly stimulated circulating memory CD8+ Tcells exhibit extended durability and protective heterosubtypic immunity relative to primary lung Trm. Parabiosis studies reveal that the enhanced durability of lung Trm after multiple antigen encounters resulted from the generation of long-lasting circulating effector memory (Tem) populations, which maintained the ability to be recruited to the lung parenchyma and converted to Trm, in combination with enhanced survival of these cells in the lung. Thus, generating a long-lasting Trm precursor pool through repeated intranasal immunizations might be a promising strategy to establish long-lasting lung Trm-mediated heterosubtypic immunity against influenza.

Abstract 1536: Enhancing CAR T cell activity by linking IL-12 expression to the endogenous PDCD1 promoter

Abstract Chimeric antigen receptor (CAR) T cells have shown great promise in treating certain late stage hematological malignancies. While very encouraging, current CAR T cell therapies have not shown the same level of success in targeting solid tumors and alternative approaches are required to achieve clinical efficacy in solid tumor patients. We describe a combinatorial approach whereby targeted gene deletion and transgene insertion occur simultaneously resulting in more potent CAR T cells for solid tumor applications. Immunomodulatory cytokines can stimulate vigorous antitumor responses and are candidates for increasing CAR T cell efficacy in solid tumors. However, the clinical application of cytokine therapy has been limited by systemic toxicity, particularly for strong effector cytokines such as IL-12. Limiting IL-12 expression to within the tumor microenvironment may reduce unwanted toxicity while enhancing CAR T cell functionality. Immune checkpoint gene programed cell death 1 (PDCD1) is a regulator of T cell functionality that is highly upregulated following T cell activation, with antibody and nuclease-mediated inactivation of the PD-1 signaling pathway having been shown to enhance CAR T cell functionality. Here, we used megaTAL genome editing/homology directed repair (HDR) to place an IL-12 transgene under the control of the PDCD1 promoter, linking IL-12 production with CAR T cell activation as well as eliminating PD-1 expression. CAR expression was combined with site specific transgene expression as follows: lentiviral vector-engineered T cells were treated with a PDCD1-specific megaTAL and transduced with adeno associated virus-6 (AAV6) containing a promoter-less IL-12 transgene flanked by PDCD1 homology regions. We observed highly efficient HDR, with inducible IL-12 expression from the endogenous PDCD1 promoter being dependent on T cell activation. Minimal IL-12 production was detected under resting conditions, whereas PMA/Ionomycin or co-culture with CAR+ target cell lines resulted in higher IL-12 secretion. Expression of IL-12 under the PDCD1 promoter enhanced CAR T cell cytokine production and cytotoxicity, especially under conditions of repeated antigen exposure. In summary, we describe a novel genome editing strategy to enhance CAR T cell functionality. Using HDR, we were able to engineer CAR T cells to simultaneously disrupt the PDCD1 gene and place a potentially therapeutic transgene under inducible transcriptional control. The IL-12/CAR T cells exhibited activation-dependent IL-12 production and enhanced cytokine and cytotoxicity responses against tumor cells in vitro. HDR may represent a promising approach to enhance CAR T cell functionality in solid tumor applications. Citation Format: Baeckseung Lee, Wai-Hang Leung, Jasdeep Mann, Kyle Havens, Joel Gay, Richard A. Morgan, Alexander Astrakhan. Enhancing CAR T cell activity by linking IL-12 expression to the endogenous PDCD1 promoter [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1536.

Human TSCM cell dynamics in vivo are compatible with long-lived immunological memory and stemness.

Adaptive immunity relies on the generation and maintenance of memory T cells to provide protection against repeated antigen exposure. It has been hypothesised that a self-renewing population of T cells, named stem cell–like memory T (TSCM) cells, are responsible for maintaining memory. However, it is not clear if the dynamics of TSCM cells in vivo are compatible with this hypothesis. To address this issue, we investigated the dynamics of TSCM cells under physiological conditions in humans in vivo using a multidisciplinary approach that combines mathematical modelling, stable isotope labelling, telomere length analysis, and cross-sectional data from vaccine recipients. We show that, unexpectedly, the average longevity of a TSCM clone is very short (half-life < 1 year, degree of self-renewal = 430 days): far too short to constitute a stem cell population. However, we also find that the TSCM population is comprised of at least 2 kinetically distinct subpopulations that turn over at different rates. Whilst one subpopulation is rapidly replaced (half-life = 5 months) and explains the rapid average turnover of the bulk TSCM population, the half-life of the other TSCM subpopulation is approximately 9 years, consistent with the longevity of the recall response. We also show that this latter population exhibited a high degree of self-renewal, with a cell residing without dying or differentiating for 15% of our lifetime. Finally, although small, the population was not subject to excessive stochasticity. We conclude that the majority of TSCM cells are not stem cell–like but that there is a subpopulation of TSCM cells whose dynamics are compatible with their putative role in the maintenance of T cell memory.

IL-7 plays a critical role for the homeostasis of allergen-specific memory CD4 T cells in the lung and airways

Memory T cells respond rapidly to repeated antigen exposure and can maintain their population for extended periods through self-renewal. These characteristics of memory T cells have mainly been studied during viral infections, whereas their existence and functions in allergic diseases have been studied incompletely. Since allergic patients can suffer repeated relapses caused by intermittent allergen exposure, we hypothesized that allergen- specific memory Th2 cells are present and the factors necessary for the maintenance of these cells are provided by the lung and airways. Using a murine model of airway inflammation, we found that allergen-specific CD4 T cells survived longer than 70 days in the lung and airways in an IL-7 dependent fashion. These T cells showing homeostatic proliferation were largely found in the mediastinal lymph node (mLN), rather than the airways; however, cells residing in the lung and airways developed recall responses successfully. We also found that CD4 T cells exhibited differential phenotypes in the mLN and in the lung. Altogether, we believe that allergen-specific memory T cells reside and function in the lung and airways, while their numbers are replenished through homeostatic turnover in the mLNs. Furthermore, we determined that IL-7 signaling is important for the homeostasis of these cells.

Peanut-specific type 1 regulatory T cells induced in vitro from allergic subjects are functionally impaired

Peanut allergy (PA) is a life-threatening condition that lacks regulator-approved treatment. Regulatory T type 1 (TR1) cells are potent suppressors of immune responses and can be induced invivo upon repeated antigen exposure or invitro by using tolerogenic dendritic cells. Whether oral immunotherapy (OIT) leads to antigen-specific TR1 cell induction has not been established. We sought to determine whether peanut-specific TR1 cells can be generated invitro from peripheral blood of patients with PA at baseline or during OIT and whether they are functional compared with peanut-specific TR1 cells induced from healthy control (HC) subjects. Tolerogenic dendritic cells were differentiated in the presence of IL-10 from PBMCs of patients with PA and HC subjects pulsed with the main peanut allergens of Arachis hypogaea, Ara h 1 and 2, and used as antigen-presenting cells for autologous CD4+ T cells (CD4+ T cells coincubated with tolerogenic dendritic cells pulsed with the main peanut allergens [pea-T10cells]). Pea-T10cells were characterized by the presence of CD49b+ lymphocyte-activation gene 3 (LAG3)+ TR1 cells, antigen-specific proliferative responses, and cytokine production. CD49b+LAG3+ TR1 cells were induced in pea-T10cells at comparable percentages from HC subjects and patients with PA. Despite their antigen specificity, pea-T10cells of patients with PA with or without OIT, as compared with those of HC subjects, were not anergic and had high TH2 cytokine production upon peanut-specific restimulation. Peanut-specific TR1 cells can be induced from HC subjects and patients with PA, but those from patients with PA are functionally defective independent of OIT. The unfavorableTR1/TH2 ratio is discussed as a possible cause ofPATR1 cell impairment.

IL-7 plays as a critical factor for the maintenance of allergen-specific memory CD4 T cells in the lung and airways

Abstract Memory T cells can respond rapidly against repeated antigen exposure, and maintain their population with extended period of time. While these characteristics of memory T cells have mainly been studied during viral infections, their roles in allergic diseases remain to be determined. Since allergic patients suffer relapses and exacerbations of the diseases by intermittent exposure to allergens, we hypothesized that allergen-specific memory CD4 T cells are present in the lung and airways and the crucial survival factors for these cells are provided in their microenvironments. In order to test this hypothesis, we transferred ovalbumin (OVA)-specific T cells into naïve Balb/c mice intravenously and induced allergic inflammation by treating these mice with a mixture of house dust mite and OVA intranasally. We found that allergen-specific memory CD4 T cells were present and survived more than 70 days in the lung and airways. In order to understand how these cells maintain their homeostasis, we blocked IL-7 signaling by treating these mice with an anti-IL-7Rα antibody. The numbers of allergen-specific memory CD4 T cells decreased in the mediastinal lymph node, lung and airways after IL-7Rα blockade. Furthermore, we found that allergen-specific memory CD4 T cells in the lung and airways induced airway inflammation regardless of T cell recruitment from circulation. In conclusion, the allergen-specific memory CD4 T cells are present in the allergic lung and airways, and the IL-7 signaling plays a critical role in the maintenance of these cells.

Defining novel parameters for the optimal priming and expansion of minor histocompatibility antigen-specific T cells in culture.

BackgroundAdoptive transfer of minor histocompatibility antigen (MiHA)-specific T cells is a promising therapy for patients with hematological cancers. However, the efficacy of the transferred cells is hampered by the acquisition of terminal effector differentiation and exhaustion features during expansion in vitro thus preventing their function and persistence in vivo. Yet, the factors that induce T-cell differentiation and functional impairment in culture remain poorly defined and are likely to vary depending on the method used for expansion.MethodsUsing the clinically relevant HLA-A0201-restricted MiHA HA-1 as well as reagents and procedures that are readily transferable to a clinical environment, we designed a novel culture protocol and defined how exhaustion features appeared in function of time. The optimal time points for the expansion of “fit” MiHA-specific T cells were delineated using phenotypic and functional assessments including KLRG-1 and PD-1 surface markers as well as Ki67 staining and cytokine secretion assays.ResultsFollowing a priming phase, an enrichment step and a rapid expansion stage, our method generates MiHA-specific T-cell lines. Evidence of phenotypic and functional dysfunction appear in function of culture duration, but display different characteristics following the extension of the priming or rapid expansion phases. While repeated antigen exposure during the priming phase induced the decline of the antigen-specific population and the expression of PD-1 and KLRG-1 on antigen-specific CD8+ T cells, the prolongation of an antigen-free expansion phase induced proliferation arrest and the relative loss of antigen-specific cells without impairing polyfunctional cytokine secretion or inducing PD-1 and KLRG-1 expression. A similar pattern was also observed after stimulating a virus-specific memory repertoire, except for the more rapid acquisition of exhaustion features upon repeated antigen exposure.ConclusionOur results offer novel insights on the impact of culture duration on the acquisition of T-cell exhaustion features. Using a new clinical-compliant protocol, we define critical parameters to monitor in order to optimally differentiate and expand MiHA-specific T cells in culture prior to adoptive transfer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0495-z) contains supplementary material, which is available to authorized users.

Repeated antigen exposure reverses endogenous CD8 T cell tolerance and is potentiated by IL-4 (MUC8P.804)

Abstract Elucidating the induction, maintenance, and reversal of self-tolerant CD8 T cells is imperative for understanding the development and progression of autoimmunity, as well as cancer. Using a mouse model that permits examination of responses to small intestinal self-antigen, we can evaluate endogenous polyclonal self-specific T cells that have undergone tolerance induction. This established CD8 T cell tolerance can be reversed after repeated antigen delivery, generating large numbers of activated, functional endogenous self-specific T cells. Interestingly, this response is reduced in IL-4 limiting conditions suggesting a mechanistic role for IL-4 in self-reactive CD8 T cells responses. We hypothesize that IL-4 is required for self-specific CD8 T cell selection, survival and/or responses to cognate antigen. We show that while IL-4 does not act directly on CD8 T cells, it does impact their proliferation, especially during Ag recognition. Interestingly, we can detect self-reactive T cells that have escaped thymic selection in unmanipulated mice, but these remain naïve, despite the presence of large amounts of cognate MHC:Ag complexes. Future studies will focus on elucidating the function and origin of IL-4 in self-specific responses and understanding properties of endogenous, polyclonal self-specific CD8 T cells in negatively selecting environments.

Cytokine-Mediated Programmed Proliferation of Virus-Specific CD8+ Memory T Cells

During infection, CD8(+) Tcells not only respond to antigenic signals through their Tcell receptor (TCR) but also incorporate inflammatory signals from cytokines produced in the local infected microenvironment. Transient TCR-mediated stimulation will result in programmed proliferation that continues despite removal of the antigenic stimulus, but it remains unclear whether brief exposure to specific cytokines will elicit similar effects. Here, we have demonstrated that brief stimulation of memory Tcells with interleukin-12 (IL-12) and interleukin-18 (IL-18) results in tightly regulated programmed proliferation, in addition to acquisition of enhanced virus-specific cytokine production and cytolytic activity. CD8(+) Tcells briefly exposed to IL-12 and IL-18 invitro showed improved antiviral activity invivo, as demonstrated by increased proliferation and reduced viremia. These results indicate that even transitory exposure to inflammatory cytokines can provide a selective advantage to infiltrating CD8(+) Tcells by triggering a developmental program that is initiated prior to direct contact with virus-infected cells.

A New Cellular Weapon to Kill Leukaemic B-Cells = سلاح خلوي جديد لقتل خلايا ( ب ) المسببة لإبيضاض الدم

A New Cellular Weapon to Kill Leukaemic B-Cells = سلاح خلوي جديد لقتل خلايا ( ب ) المسببة لإبيضاض الدم

Retrovirally expressed 4-1BBL dramatically increases proliferation and in vivo persistence of adoptively transferred CD19-targeted T cells, promoting complete tumor elimination. (131.16)

Abstract Human T cells transduced with a chimeric antigen receptor (CAR) composed of an antibody-derived scFv fragment and the CD3ζ chain can recognize and kill tumor cells on binding to the targeted membrane antigen. The co-transduction of a CAR along with CD80 and 4-1BBL induces auto-costimulation enabling high in vivo T cell expansion and tumor rejection in a prostate tumor model. Here we investigated this concept in T cells harboring either a first generation anti-CD19 CAR (19z1) or a second generation CAR (1928z), which additionally comprises the CD28 cytoplasmic domain. We compared the proliferation and anti-tumor activity of 19z1+, 19z1-4-1BBL+, 19z1-CD80+4-1BBL+, 1928z+ and 1928z-4-1BBL+ transduced T cells in a pro B cell leukemia model (NALM-6). Seven days after IV injection into NALM-6 bearing NOD/SCID/IL2Rγnull mice, 1928z-4-1BBL+ CD8 and CD4 T cells accumulated in the bone marrow and the spleen 100 times more than 19z1+ T cells and 10 times more than 1928z+ T cells, corroborating in vitro proliferative responses to repeated antigen exposure. An increased proportion of central memory CD8 T cells was observed in all groups treated with 4-1BBL-expressing cells. Within 15 days, in vivo bioluminescence imaging showed total tumor regression in the 1928z-4-1BBL+ T cell-treated group and partial regression in the other groups. Thus, constitutive 4-1BBL expression drives high proliferation of anti-tumor CD8 T cells, promoting central memory T cell persistence and tumor eradication.

An aged T cell phenotype: A prognostic indicator in liver transplant recipients?

There is now little doubt that aging has a profound effect on both the innate and adaptive arms of the immune system that results in a decline in immunity termed immunosenescence. This is evidenced by increased susceptibility to bacterial and viral infections, reactivation of latent infections (herpes zoster leading to shingles), increased production of autoantibodies, and decreased response to vaccination in older adults. Two key drivers for senescence in the adaptive immune system are thymic involution, which reduces the output of naive T cells, and consequent homeostatic expansion of the peripheral T cell pool. Moreover, with repeated antigen exposure and proliferation of memory T cells throughout life, there is also shortening of telomeres, which limits the proliferative capacity of T cells and eventually results in replicative senescence. With repeated stimulation, T cells also become highly differentiated: they lose costimulatory receptors such as CD28, CD27, cytotoxic T lymphocyte antigen 4, and inducible T cell costimulator, up-regulate inhibitory receptors such as killer cell lectin-like receptor subfamily G member 1, and acquire expression of immune effector molecules, including killer cell immunoglobulin-like receptors, chemokines, and chemokine receptors. Each of these factors contributes to the agerelated loss of T cell responsiveness and can be considered a biomarker for the biological age of an individual’s immune system. Importantly, longitudinal studies have revealed that T cell immunosenescence is associated with increased morbidity and mortality, and specific age-related changes in the T cell phenotype have been proposed to represent an immune risk phenotype. Shortened leukocyte telomeres are associated with several agerelated pathologies, including cardiovascular disease and cancer, and the number of CD4þCD28 T cells is increased in patients with autoimmune inflammatory diseases such as rheumatoid arthritis. In this issue of Liver Transplantation, Gelson et al. report on their investigation of whether the chronic immune stress of organ transplantation accelerates aging of the immune system. It has already been well documented in the literature that transplant recipients have an increased incidence of cancer, cardiovascular disease, and infections, but this has been largely ascribed to the effects of the long-term use of immunosuppressants. However, the authors show clearly that another possible factor contributing to excess morbidity and mortality in established organ graft recipients is senescence of the immune system as liver graft recipients had shorter T cell telomeres and more cells of a mature phenotype than healthy age-matched controls. Interestingly, multiple linear regression analyses of case and control data have allowed Gelson et al. to estimate the impact of organ grafts and comorbidities on T cell telomere length, and this has allowed them to gauge the effect in terms of relative T cell aging. Thus, those patients with established liver grafts had 1 year added to their T cells’ biological clock, whereas patients with hepatocellular carcinoma at transplantation or skin malignancy subsequent to transplantation had 6.2 and 3.7 additional years, respectively. Crucially, the use of immunosuppressive drugs was not independently associated with shortened telomeres or an increase in cells with a mature

Upregulation of geranylgeranyltransferase I in bronchial smooth muscle of mouse experimental asthma: its inhibition by lovastatin

RhoA has been recognized as an important protein for bronchial smooth muscle (BSM) contraction and hyperresponsiveness, and its activation is also regulated by geranylgeranyltransferase I (GGTase I). In the present study, the effects of repeated antigen exposure on the expression of GGTase I were determined in mouse BSMs. Male BALB/c mice were sensitized and repeatedly challenged with ovalbumin antigen. Animals were also treated with lovastatin (4 mg/kg/day, i.p.) once a day prior to and during the antigen inhalation period. Western blot analyses revealed that GGTase I was upregulated in BSMs of the antigen-challenged mice. The systemic treatment with lovastatin attenuated the upregulation of GGTase I induced by antigen exposure. Interestingly, lovastatin also significantly reduced the protein expression of GGTase I in BSMs of control animals. We thus concluded that an upregulation of GGTase I in BSM might be, at least in part, involved in the development of antigen-induced airway hyperresponsiveness. Lovastatin might have therapeutic potential to ameliorate airway hyperresponsiveness in allergic bronchial asthma.

The CD8+ memory T-cell state of readiness is actively maintained and reversible

AbstractThe ability of the adaptive immune system to respond rapidly and robustly upon repeated antigen exposure is known as immunologic memory, and it is thought that acquisition of memory T-cell function is an irreversible differentiation event. In this study, we report that many phenotypic and functional characteristics of antigen-specific CD8 memory T cells are lost when they are deprived of contact with dendritic cells. Under these circumstances, memory T cells reverted from G1 to the G0 cell-cycle state and responded to stimulation like naive T cells, as assessed by proliferation, dependence upon costimulation, and interferon-γ production, without losing cell surface markers associated with memory. The memory state was maintained by signaling via members of the tumor necrosis factor receptor superfamily, CD27 and 4-1BB. Foxo1, a transcription factor involved in T-cell quiescence, was reduced in memory cells, and stimulation of naive CD8 cells via CD27 caused Foxo1 to be phosphorylated and emigrate from the nucleus in a phosphatidylinositol-3 kinase–dependent manner. Consistent with these results, maintenance of G1 in vivo was compromised in antigen-specific memory T cells in vesicular stomatitis virus-infected CD27-deficient mice. Therefore, sustaining the functional phenotype of T memory cells requires active signaling and maintenance.

The CD8+ T cell memory state of readiness is actively maintained and reversible (83.18)

Abstract The ability of the adaptive immune system to respond rapidly and robustly upon repeated antigen exposure is known as immunologic memory, and it is thought that T cell progression from the naïve to the memory state is an irreversible differentiation event. Here we report that unlike naïve T cells, which are in the G0 phase of the cell cycle, CD8+ memory T cells exist in a state of readiness in G1. This was maintained by occupancy of members the TNF receptor superfamily, CD27 and 4-1BB, which when disrupted caused memory T cells to revert to G0 and respond like naïve T cells to stimulation. Furthermore, maintenance of the G1 state was compromised in antigen-specific memory T cells of VSV-infected CD27-deficient mice. Manipulating the memory T cell state of readiness might benefit disorders involving chronic ongoing immune responses. This work was supported by the Intramural Research Program of the National Institutes of Health, Center for Cancer Research, National Cancer Institute

T‐cell tolerance induced by repeated antigen stimulation: Selective loss of Foxp3− conventional CD4 T cells and induction of CD4 T‐cell anergy

Repeated immunization of mice with bacterial superantigens induces extensive deletion and anergy of reactive CD4 T cells. Here we report that the in vitro proliferation anergy of CD4 T cells from TCR transgenic mice immunized three times with staphylococcal enterotoxin B (SEB) (3 x SEB) is partially due to an increased frequency of Foxp3(+) CD4 T cells. Importantly, reduced number of conventional CD25(-) Foxp3(-) cells, rather than conversion of such cells to Foxp3(+) cells, was the cause of that increase and was also seen in mice repeatedly immunized with OVA (3 x OVA) and OVA-peptide (OVAp) (3 x OVAp). Cell-transfer experiments revealed profound but transient anergy of CD4 T cells isolated from 3 x OVAp and 3x SEB mice. However, the in vivo anergy was CD4 T-cell autonomous and independent of Foxp3(+) Treg. Finally, proliferation of transferred CD4 T cells was inhibited in repeatedly immunized mice but inhibition was lost when transfer was delayed, despite the maintenance of elevated frequency of Foxp3(+) cells. These data provide important implications for Foxp3(+) cell-mediated tolerance in situations of repeated antigen exposure such as human persistent infections.