Homeostatic Proliferation Of CD8 Research Articles

A Delayed HIV Infection Model with the Homeostatic Proliferation of CD4+ T Cells

A Delayed HIV Infection Model with the Homeostatic Proliferation of CD4+ T Cells

Psoriatic Inflammation Facilitates the Onset of Arthritis in a Mouse Model

Psoriatic arthritis (PsA) is a seronegative, inflammatory joint disease associated with psoriasis. In most patients with PsA, skin lesions precede arthritis; however, the causality of skin inflammation for the development of arthritis remains unclear. Gp130F759/F759 knock-in (F759) mice develop autoimmune arthritis after 1 year of age through persistent signal transducer and activator of transcription 3 (Stat3) activation due to impairment in SOCS3-dependent negative regulation. Here, we crossed F759 mice with K5.Stat3C transgenic mice, in which keratinocytes express constitutive active Stat3 (Stat3C), leading to generation of psoriasis-like skin change. F759 mice harboring the K5.Stat3C transgene not only had aggravated skin lesions but also spontaneously developed arthritis with high penetrance in adjacent paws as early as 3 weeks of age. The joint lesions included swelling of the peripheral paws and nail deformities contiguous with the skin lesions, closely resembling PsA. Histopathologic study revealed enthesitis and bone erosions, with mononuclear cell infiltrates. Quantitative reverse transcriptase-PCR (RT-PCR), immunohistochemical analyses, and flow cytometry showed upregulation of the IL-23/T helper type 17 (Th17) pathway in affected joints. Furthermore, enforced generation of psoriasis-like skin inflammation by topical treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) in F759 mice induced swelling of the underlying joints. This animal model renders psoriatic inflammation as the driver of arthritis and helps to further understand the pathogenesis of PsA.

OX40 and IL-7 play synergistic roles in the homeostatic proliferation of effector memory CD4⁺ T cells.

T-cell homeostasis preserves the numbers, the diversity and functional competence of different T-cell subsets that are required for adaptive immunity. Naïve CD4(+) T (TN ) cells are maintained in the periphery via the common γ-chain family cytokine IL-7 and weak antigenic signals. However, it is not clear how memory CD4(+) T-cell subsets are maintained in the periphery and which factors are responsible for the maintenance. To examine the homeostatic mechanisms, CFSE-labeled CD4(+) CD44(high) CD62L(low) effector memory T (TEM ) cells were transferred into sublethally-irradiated syngeneic C57BL/6 mice, and the systemic cell proliferative responses, which can be divided distinctively into fast and slow proliferations, were assessed by CFSE dye dilution. We found that the fast homeostatic proliferation of TEM cells was strictly regulated by both antigen and OX40 costimulatory signals and that the slow proliferation was dependent on IL-7. The simultaneous blockade of both OX40 and IL-7 signaling completely inhibited the both fast and slow proliferation. The antigen- and OX40-dependent fast proliferation preferentially expanded IL-17-producing helper Tcells (Th17 cells). Thus, OX40 and IL-7 play synergistic, but distinct roles in the homeostatic proliferation of CD4(+) TEM cells.

Regulator of Fatty Acid Metabolism, Acetyl Coenzyme A Carboxylase 1, Controls T Cell Immunity

Fatty acids (FAs) are essential constituents of cell membranes, signaling molecules, and bioenergetic substrates. Because CD8(+) T cells undergo both functional and metabolic changes during activation and differentiation, dynamic changes in FA metabolism also occur. However, the contributions of de novo lipogenesis to acquisition and maintenance of CD8(+) T cell function are unclear. In this article, we demonstrate the role of FA synthesis in CD8(+) T cell immunity. T cell-specific deletion of acetyl coenzyme A carboxylase 1 (ACC1), an enzyme that catalyzes conversion of acetyl coenzyme A to malonyl coenzyme A, a carbon donor for long-chain FA synthesis, resulted in impaired peripheral persistence and homeostatic proliferation of CD8(+) T cells in naive mice. Loss of ACC1 did not compromise effector CD8(+) T cell differentiation upon listeria infection but did result in a severe defect in Ag-specific CD8(+) T cell accumulation because of increased death of proliferating cells. Furthermore, in vitro mitogenic stimulation demonstrated that defective blasting and survival of ACC1-deficient CD8(+) T cells could be rescued by provision of exogenous FA. These results suggest an essential role for ACC1-mediated de novo lipogenesis as a regulator of CD8(+) T cell expansion, and may provide insights for therapeutic targets for interventions in autoimmune diseases, cancer, and chronic infections.

TCR triggering modulates the responsiveness and homeostatic proliferation of CD4+ thymic emigrants to IL-7 therapy

AbstractInterleukin-7 (IL-7) is currently used in clinical trials to augment T-cell counts. Paradoxically, elevated systemic IL-7 found in lymphopenic humans is typically insufficient for CD4+ T-cell regeneration, and thymopoiesis becomes critical in this process. Here we show that the proliferative effect of IL-7 is more pronounced on CD4+CD8− thymocytes compared with peripheral CD4+ T cells. These cells express miR181a at higher levels and respond to lower concentrations of IL-7. As single-positive CD4+ thymocytes (CD4+SPT) exit the thymus, they rapidly diminish their proliferation to IL-7 therapy, and this is mediated, at least in part, by major histocompatibility complex class II distribution outside the thymus. Interestingly, increasing T-cell receptor (TCR) stimulation augments IL-7 responsiveness and proliferation of peripheral CD4+ T cells, whereas failure to stimulate TCR abrogates proliferation induced by IL-7. Finally, we demonstrated that IL-7 enhances the proliferation of CD4+ T cells that undergo “slow proliferation” in lymphopenic hosts. To date, our results indicate that TCR signaling is a major controlling factor for CD4 responsiveness and proliferation to IL-7 therapy.

AB0122 Regulatory t cell abnormalities and il-2 deficiency in patients with systemic lupus erythematosus

BackgroundQuantitative and qualitative aberrations of CD4+ Foxp3+ regulatory T cells (Treg) have been associated with systemic lupus erythematosus (SLE). In addition, impaired production of IL-2 by T cells has been...

Critical Role of STAT5 Transcription Factor Tetramerization for Cytokine Responses and Normal Immune Function

Cytokine-activated STAT proteins dimerize and bind to high-affinity motifs, and N-terminal domain-mediated oligomerization of dimers allows tetramer formation and binding to low-affinity tandem motifs, but the functions of dimers versus tetramers are unknown. We generated Stat5a-Stat5b double knockin (DKI) N-domain mutant mice in which STAT5 proteins form dimers but not tetramers, identified cytokine-regulated genes whose expression required STAT5 tetramers, and defined dimer versus tetramer consensus motifs. Whereas Stat5-deficient mice exhibited perinatal lethality, DKI mice were viable; thus, STAT5 dimers were sufficient for survival. Nevertheless, STAT5 DKI mice had fewer CD4(+)CD25(+) T cells, NK cells, and CD8(+) T cells, with impaired cytokine-induced and homeostatic proliferation of CD8(+) T cells. Moreover, DKI CD8(+) T cell proliferation after viral infection was diminished and DKI Treg cells did not efficiently control colitis. Thus, tetramerization of STAT5 is critical for cytokine responses and normal immune function, establishing a critical role for STAT5 tetramerization in vivo.

Interleukin-15 enhances T-cell responses by stimulation with dendritic cells

Cytokines play important roles in regulating immune responses. Interleukin-2 (IL-2) has usually been used as an adjuvant to enhance antitumour immune responses. However, its crucial role in activation-induced cell death, inhibition of homeostatic proliferation of CD8+ memory T cells and its notable biological side effects impair its prospect of application. IL-15 has several similar functions to IL-2 and shows potential advantages over IL-2, and is being investigated to enhance antitumour dendritic cell (DC) vaccine strategies in our ongoing studies. In this preliminary study, we evaluated the ability of IL-15, compared with IL-2, to act as an adjuvant to enhance T-cell responses activated by DCs in vitro. Bone marrow-derived DCs (BMDCs) were pulsed with tumour antigens and used to stimulate lymphocyte responses in the presence of IL-15 or IL-2. The activated T lymphocytes were examined by flow cytometric analysis, and interferon-γ (IFN-γ) enzyme-linked immunospot and cytotoxicity assays. IL-15 was observed to activate lymphocytes with comparable phenotype characteristics of activated/memory CD8+ lymphocytes, compared with IL-2. Both in primary and secondary stimulation with DCs, when using IL-15 as an adjuvant, activated lymphocytes showed higher proportions of IFN-γ-secreting subsets. In secondary stimulation with BMDCs in the presence of IL-15, the activated lymphocytes showed a stronger cytotoxicity to antigen-specific tumour target cells. Our study suggested that IL-15 might be a prospective adjuvant for a DC vaccine strategy against cancers. The further observation that IL-15 acts as an adjuvant for an antitumour DC vaccine strategy is worth investigating.

Apoptosis regulators Fas and Bim synergistically control T-lymphocyte homeostatic proliferation

The size of the peripheral T-lymphocyte compartment is governed by complex homeostatic mechanisms that balance T-cell proliferation and death. Proliferation and survival signals are mediated in part by recurrent self-peptide/MHC-TCR interactions and signaling by the common γ chain-containing cytokine receptors, including those for IL-7 and IL-15. We have previously shown that the death receptor Fas (CD95/APO-1) regulates apoptosis in response to repeated TCR stimulation, whereas the Bcl-2 homology domain 3-only protein Bim mediates cytokine withdrawal-induced apoptosis. We therefore reasoned that these two molecules might cooperate in the regulation of homeostatic proliferation. In this study, we observe that the combined loss of Fas and Bim synergistically enhances the accumulation of T cells in lymphopenic host mice, and this is particularly pronounced for the unusual CD4(-) CD8(-) TCRαβ(+) T cells that are characteristic of Fas-deficient (Fas(lpr/lpr) ) mice. Our findings demonstrate that these CD4(-) CD8(-) TCRαβ(+) T cells arise from homeostatic proliferation of CD8(+) T cells. These studies also underscore the profound rate of baseline T-cell proliferation that likely occurs in wild-type mice even in the absence of foreign antigen, and the consequent need for its coordinated regulation by multiple death-signaling pathways.

Abstract 4782: Expression of programmed death-1 in CD8+ T cells from patients bearing PCA upon stimulation with common γ-chain cytokines

Abstract Prostate cancer (PCA) is a leading cause of cancer death in men. Underlying immunosuppressive mechanisms in benign prostate hyperplasia (BPH) and PCA patients are not fully clarified. We analyzed homeostatic proliferation of CD8+ T cells upon stimulation with common receptor γ chain IL-2, IL-7 and IL-15 cytokines in PCA as compared to BPH patients. CD8+ T cells exhaustion was assessed by evaluating Programmed Death-1 (PD-1) receptor and its ligand PD-L1 expression in PBMC and tissue infiltrating CD8+ T cells from PCA and BPH patients. 57 BPH and 76 PCA patients were enrolled. Gene expression was quantified by Real-Time PCR. T cell proliferation was evaluated by CFSE dilution. CD132, CD122, PD-1 and PD-Ll expression were assessed by flow cytometry. IL-2, IL-7 and IL-15 gene expression were quantified in PCA (n=57) and BPH (n=32) tissues. IL-7 and IL-15 gene expression were significantly increased in PCA tissues as compared to BPH (p=0.024; p=0.031). No significant differences were observed for IL-2 gene expression. CD8+ cells from BPH (n=17) and PCA (n=21) patients showed a significantly decreased responsiveness to IL-7 and IL-15 (p=0.021; p=0.015) as compared to healthy donors (n=9). Response to IL-2 was similar. A trend towards a lower response to IL-15 in PCA as compared to BPH patients was detectable. Percentage of CD8+ T cells expressing the common γ chain (CD132) of homeostatic cytokines receptor is significantly decreased in PCA (n=13) and BPH (n=16) patients as compared to healthy donors (n=8) (p= 0.024; p<0.001). Percentage of CD8+ T cells expressing the common β chain (CD122) is significantly decreased in PCA patients as compared to healthy donors (p=0.035). No significant differences were noticed for the expression of the α chain of homeostatic cytokine receptor. Urged by these findings, we addressed the expression of PD-1 and its ligand in CD8+ T cells from BPH and PCA patients. In BPH (n=7) and PCA (n=7), %CD8+PD-1+ and %CD8+PD-L1+ T cells are increasing upon culture with homeostatic cytokines. In freshly isolated CD8+ cells, a highly significant increase in the %CD8+PD-1+ cells was observed in PCA (n=32) and BPH (n=22) as compared to healthy donors (p<0.001; p<0.001). In contrast, PD-L1 expression in CD8+ cells was similar in BPH and PCA patients and in healthy donors. A large majority of CD8+ cells infiltrating BPH or PCA tissues (83±22% for BPH, n=9; 88±17% for PCA, n=7) were PD-1+, whereas PD-L1 was expressed in 51±43% and 37±39% of infiltrating CD8+ T cells in BPH and PCA, respectively. Taken together these data indicate that both BPH and PCA patients display a decreased responsiveness to IL-7 and IL-15 homeostatic cytokines. Interestingly, high percentages of peripheral blood CD8+ T cells express PD-1 in BPH and PCA patients. Notably, PD-1 and its ligand are highly expressed in tissue infiltrating CD8+ T cells in BPH and PCA patients, thus raising the issue of the role of T cells exhaustion in PCA. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4782.

Homeostatic proliferation of naïve CD8+ T cells depends on CD62L/L‐selectin‐mediated homing to peripheral LN

Adoptive transfer of naïve CD8(+) T cells into lymphopenic recipients results both in spontaneous proliferation and in partial activation of T cells, a phenomenon termed homeostatic proliferation (HP). HP of CD8(+) T cells is dependent on host IL-7, IL-15, and MHC-class I and has been shown to prevent T-cell tolerance, reverse T-cell anergy and support T-cell-mediated tumor control in vivo. However, the initial anatomic site of HP is still under debate. Since we observed that the earliest detectable HP occurs within LN and that T cells undergoing HP retain a CD62L(bright) phenotype, we investigated the functional role of CD62L for this process. We found that CD62L-expression on T cells is required for optimal HP and HP was impaired in lymphotoxin-alphabeta(-/-) mice, indicating the necessity for intact host secondary lymphoid organ structures. Use of the LN egression inhibitor FTY720 indicated that LN structures were pivotal to yield homeostatically proliferated T cells detected in other compartments. Consistent with these results, HP-supported control of MC57-SIY tumors depended on CD62L. Our data indicate a critical role for CD62L and LN homing for the process of HP, which has implications for adoptive immunotherapy approaches of cancer.

Low MHC-I density impairs the homeostatic proliferation of CD8 T cells after HSCT

We hypothesise that the modifications in the Major Histocompatibility Class I (MHC-I) expression after Hematopoietic Stem Cell Transplantation (HSCT) might impact on CD8 T cell recovery. To evaluate our proposal, we measured the number of peripheral CD8 T cells and the MHC-I expression on the monocytes from the patients who underwent allogenic or autologous HSCT. Three months after transplantation, almost all of the autologous recipients showed a high density of MHC-I and the CD8 T cell counts were within the normal range. In contrast, allogeneic recipients had low or heterogeneous expression of MHC-I and low numbers of CD8 T cells. Similar patterns were observed even after 6 to 20 months after transplantation. Recent thymic emigrants and serum levels of IL-7 and IL-15 were similar within both groups of patients. Together, our results indicate that Homeostatic Peripheral Expansion (HPE) is the main mechanism to reach the normal numbers of CD8 T cells immediately after HSCT. A high and homogenous expression of MHC-I molecules is required for an optimal HPE.

Dangers of restocking T cells

Refilling an empty niche with proliferating CD8+ T cells can cause autoimmune disease, say Tajima et al. (page 1019). Figure 1 Autoimmune colitis (top) caused by homeostatically proliferating CD8+ T cells is resolved in mice injected with anti–IL-6 antibody (bottom). Infusion of naive T cells into an environment where there are few native T cells—such as in patients undergoing cancer therapy—spurs two kinds of proliferation. T cells activated by non-self-peptide/MHC complexes proliferate rapidly, whereas those activated by self-peptide/MHC in the presence of cytokines such as IL-7 and IL-15 proliferate slowly. CD4+ T cells that proliferate by these methods have previously been shown to drive the inflammation seen in several autoimmune diseases. Tajima et al. now find a new variation in homeostatic proliferation of CD8+ T cells that also induces autoimmunity. In gut lymph nodes of T cell–deficient mice, injected CD8+ T cells proliferated rapidly in response to IL-6. This inflammatory cytokine was found at high levels in these lymph nodes, perhaps due to their proximity to the bacterium-laden gut. The mice developed a thicker gut epithelium and lost weight—signs of an autoimmune disease called colitis. T cell–injected mice treated with an IL-6–blocking antibody or with bacterium-depleting drugs, however, remained healthy. The proliferating T cells secreted several inflammatory cytokines, including IL-17. The IL-17 alone seemed to be responsible for the colitis, as mice injected with T cells that were unable to produce IL-17 remained healthy. If these IL-17–producing CD8+ T cells are found in patients suffering from diseases such as colitis, the anti–IL-6 antibody might be a good therapeutic option.

Differential roles for OX40 and IL‐7 on homeostasis of effector memory CD4 + T cells

Homeostatic proliferation of T cells is critically involved in the generation and maintenance of memory T cells. Recent studies have focused much attention on the crucial roles of MHC-TCR interaction and cytokines, such as IL-7 and IL-15, in the homeostatic control of memory CD4+ T cells. However, the role for costimulatory signals on the homeostatic proliferation of CD4+ T cells remains controversial although costimulatory signals contribute to the optimal proliferation and survival of T cells. To address the roles for signals through a T cell costimulatory molecule, OX40 on the homeostatic proliferation of effector memory CD4+ T cells, we have set up several experimental settings, in which polyclonal effector memory (CD44highCD62Llow) CD4+ T cells were transferred into lymphopenic recipient mice. Treatment with blocking anti-OX40L mAb during homeostatic proliferation of effector memory CD4+ T cells specifically suppressed the rapidly-proliferating MHC II-dependent cells. In contrast, inhibition of IL-7 signals by administration of blocking anti-IL-7Rα mAb during homeostatic proliferation demonstrated a preferential reduction of the slowly-proliferating population. Furthermore, simultaneous blockade of both OX40 and IL-7 signals completely inhibited the homeostatic proliferation of effector memory CD4+ T cells by suppressing both the rapid and slow homeostatic proliferation. Collectively, OX40 signals contribute to the homeostasis of effector memory CD4+ T cells in an IL-7-independent manner. This work was supported in part by a grant-in-aid for scientific research from the Japan Society for the Promotion of Science.

Spontaneous and Homeostatic Proliferation of CD4 T Cells Are Regulated by Different Mechanisms

Transfer of naive CD4 T cells into lymphopenic mice initiates a proliferative response of the transferred cells, often referred to as homeostatic proliferation. Careful analysis reveals that some of the transferred cells proliferate rapidly and undergo robust differentiation to memory cells, a process we have designated spontaneous proliferation, and other cells proliferate relatively slowly and show more limited evidence of differentiation. In this study we report that spontaneous proliferation is IL-7 independent, whereas the slow proliferation (referred to as homeostatic proliferation) is IL-7 dependent. Administration of IL-7 induces homeostatic proliferation of naive CD4 T cells even within wild-type recipients. Moreover, the activation/differentiation pattern of the two responses are clearly distinguishable, indicating that different activation mechanisms may be involved. Our results reveal the complexity and heterogeneity of lymphopenia-driven T cell proliferation and suggest that they may have fundamentally distinct roles in the maintenance of CD4 T cell homeostasis.

Cutting edge: IL-7-dependent homeostatic proliferation of CD8+ T cells in neonatal mice allows the generation of long-lived natural memory T cells.

Healthy, nonimmunized C57BL/6 (B6) mice contain memory phenotype CD8+ T cells, which are assumed to be generated in response to environmental Ags. Since neonatal mice are functionally lymphopenic within the first days after birth, we investigated the alternative possibility that the memory CD8+ T cells of untreated B6 mice are the result of lymphopenia-induced proliferation during neonatal life. We show here that adoptively transferred CD8+ T cells proliferate in neonatal B6 mice, rapidly produce IFN-gamma, and develop into memory cells which are maintained until adulthood. In contrast to CD4+ T cells, neonatal lymphopenia-induced proliferation of CD8+ T cells was IL-7 dependent. Thus, neonatal lymphopenia seems to allow CD8+ thymic emigrants to undergo lymphopenia-induced proliferation during early neonatal life to equip the immune system with a set of preactivated CD8+ T cells before any infection, which might contribute to the rapid initiation of immune responses in the adult.

The Effect of Burn Injury on Homeostatic Proliferation of CD4+ and CD8+ T Cells

The Effect of Burn Injury on Homeostatic Proliferation of CD4+ and CD8+ T Cells

A closer look at homeostatic proliferation of CD4+ T cells: costimulatory requirements and role in memory formation.

Ag-specific proliferation of CD4+ T cells is regulated, in part, by costimulatory signals through CD28. The proliferative response during primary activation is an important determinant of the ability of the T cell to respond to Ag re-encounter. Proliferation of mature CD4+ T cells during lymphopenia (homeostatic proliferation) requires interaction with endogenous peptide MHC. However, the role of costimulation during homeostatic proliferation is unclear, as is the ability of homeostatic proliferation to regulate secondary T cell responses. Using a TCR transgenic system and serial adoptive transfers we find that homeostatic proliferation of CD4+ T cells occurs for at least 5 wk after adoptive transfer into recombination-activating gene (RAG)-/- recipients. Two discrete populations of proliferating T cells can be resolved, one that is highly proliferative and dependent on CD28 signaling, and the other that contains cells undergoing low levels of CD28-independent proliferation. Importantly, naive CD4+ T cells that have undergone homeostatic proliferation acquire both phenotypic and functional characteristics of true memory cells. These studies indicate that functional memory T cells can be generated by encounters with endogenous Ags only. This mechanism of T cell regeneration is possibly active during lymphopenia due to viral infections, such as HIV, transplantation, or cancer therapy, and may explain selected autoimmune diseases.