In vivo CD86 blockade inhibits CD4+ T cell activation, whereas CD80 blockade potentiates CD8+ T cell activation and CTL effector function

Chimeric antigen receptor macrophages activated through TLR4 or IFN-γ receptors suppress breast cancer growth by targeting VEGFR2

Chimeric antigen receptor macrophage (CAR-M) is a promising immunotherapy strategy of anti-tumor due to its high infiltration, direct phagocytosis of tumor cells, immunomodulation of tumor microenvironment (TME) and linkage of innate and adaptive immunity. Here a series of novelly designed CAR-Ms by targeting vascular endothelial growth factor receptor-2 (VEGFR2), which highly expressed in tumor cells and TME, were evaluated. Their activation signals were transduced by Tlr4 or Ifn-γ receptors either alone or in combination, which were designed to mediate M1 polarization of macrophages as the downstream of lipopolysaccharide or Ifn-γ that had been widely reported. Our results showed that VEGFR2-targeting CAR-Ms could be activated under the stimulation of VEGFR2-expressing cells. They exhibited higher expression of CD86, MHCII and TNF-α in vitro and enhanced tumor suppressive abilities in vivo. Implantation of these CAR-Ms into 4T1 breast cancer-bearing mice could obviously inhibit the progression of tumor without significant toxic side effects, especially the group of mmC in which constructed with Tlr4 as the intracellular domain of CAR. In conclusion, this research provides a promising design of CAR that induce macrophages activation by Tlr4 and/or Ifn-γ receptors, and these CAR-Ms could effectively inhibit tumor growth through targeting VEGFR2.

Resistance to immune checkpoint blockade: Mechanisms, counter-acting approaches, and future directions

Immunotherapies seek to unleash the immune system against cancer cells. While a variety of immunotherapies exist, one of the most commonly used is immune checkpoint blockade, which refers to the use of antibodies to interfere with immunosuppressive signaling through immune checkpoint molecules. Therapies against various checkpoints have had success in the clinic across cancer types. However, the efficacy of checkpoint inhibitors has varied across different cancer types and non-responsive patient populations have emerged. Non-responders to these therapies have highlighted the importance of understanding underlying mechanisms of resistance in order to predict which patients will respond and to tailor individual treatment paradigms. In this review we discuss the literature surrounding tumor mediated mechanisms of immune checkpoint resistance. We also describe efforts to overcome resistance and combine checkpoint inhibitors with additional immunotherapies. Finally, we provide insight into the future of immune checkpoint blockade, including the need for improved preclinical modeling and predictive biomarkers to facilitate personalized cancer treatments for patients.

A MLR-Based Approach to Analyze Regulators of T Lymphocyte Activation In Vivo

Depending on the context, robust and durable T lymphocyte activation is either desirable, as in the case of anti-tumor responses, or unwanted, in cases of autoimmunity when chronic stimulation leads to self-tissue damage. Therefore, reliable in vivo models are of great importance to identify and validate regulatory pathways of T lymphocyte activation. Here, we describe an in vivo mixed-lymphocyte-reaction (MLR) approach, which is based on the so-called parent-into-F1 (P → F1) mouse model in combination with the congenic marker CD45.1/2 and cell proliferation dye-labeling. This setup allows us to track adoptively transferred allogenic CD4⁺ and CD8⁺ T lymphocytes and analyze their phenotype as well as the proliferation by flow cytometry in the blood and spleen. We could show hypo-reactive responses of T lymphocytes isolated from knockout mice with a known defect in T lymphocyte activation. Thus, this MLR-based in vivo model provides the opportunity to analyze positive regulators of T cell responses under physiological conditions of polyclonal T lymphocyte activation in vivo.

Sporothrix globosa melanin inhibits antigenpresentation by macrophages and enhances deep organ dissemination

Melanin is a Sporothrix virulence factor that can inhibit the innate immune functions of macrophages such as phagocytosis and killing. However, no data on melanin's influence on antigen presentation by macrophages are available. In this study, we used conidia, yeasts, and melanin ghosts (MGs) from a black Sporothrix globosa strain (MEL+) and its ultraviolet-induced albino mutant (MEL-), to study the influence of melanin on expression of molecules involved in antigen presentation by mouse macrophages (MHC class II, CD80, CD86), as well as on levels of transcription factors regulating their expression (CIITA and promoters I, III, and IV). A murine infection model was used to assess the virulence of both strains and differences in expression of MHC class II and CD80/86 in vivo. MHC class II, CD86 CIITA, and PIV expressions were lower in macrophages infected with MEL+ than in macrophages infected with MEL- conidia, while CD80 expression was similar. No statistical difference in gene expression was observed between macrophages infected by MEL+ and MEL- yeasts. Infection by MGs alone had no clear effect on expression of antigen presentation-associated molecules. Mice infected with MEL+ S. globosa had significantly higher fungal burdens in the lung, liver, spleen, kidney, and testicle compared with mice infected with MEL- S. globosa 21 days post-infection. MHC class II expression changes in the animal study were similar to those observed in the in vitro experiment. Our results indicate that S. globosa melanin can inhibit expression of antigen presentation-associated molecules during both the early and late stages of infection, representing a new mechanism to evade host immunity and to enhance dissemination. Further investigations of melanin's impact on adaptive immunity will be helpful in understanding this fungal virulence factor.

Novel identified aluminum hydroxide-induced pathways prove monocyte activation and pro-inflammatory preparedness

Aluminum-based adjuvants are the most widely used adjuvants in human vaccines. A comprehensive understanding of the mechanism of action of aluminum adjuvants at the molecular level, however, is still elusive. Here, we unravel the effects of aluminum hydroxide Al(OH)₃ by a systems-wide analysis of the Al(OH)₃-induced monocyte response. Cell response analysis by cytokine release was combined with (targeted) transcriptome and full proteome analysis. Results from this comprehensive study revealed two novel pathways to become activated upon monocyte stimulation with Al(OH)₃: the first pathway was IFNβ signaling possibly induced by DAMP sensing pathways like TLR or NOD1 activation, and second the HLA class I antigen processing and presentation pathway. Furthermore, known mechanisms of the adjuvant activity of Al(OH)₃ were elucidated in more detail such as inflammasome and complement activation, homeostasis and HLA-class II upregulation, possibly related to increased IFNγ gene expression. Altogether, our study revealed which immunological pathways are activated upon stimulation of monocytes with Al(OH)₃, refining our knowledge on the adjuvant effect of Al(OH)₃ in primary monocytes.

SIGNIFICANCE

Aluminum salts are the most used adjuvants in human vaccines but a comprehensive understanding of the working mechanism of alum adjuvants at the molecular level is still elusive. Our Systems Vaccinology approach, combining complementary molecular biological, immunological and mass spectrometry-based techniques gave a detailed insight in the molecular mechanisms and pathways induced by Al(OH)₃ in primary monocytes. Several novel immunological relevant cellular pathways were identified: type I interferon secretion potentially induced by TLR and/or NOD like signaling, the activation of the inflammasome and the HLA Class-I and Class-II antigen presenting pathways induced by IFNγ. This study highlights the mechanisms of the most commonly used adjuvant in human vaccines by combing proteomics, transcriptomics and cytokine analysis revealing new potential mechanisms of action for Al(OH)₃.

Conventional CD4+ T cells present bacterial antigens to induce cytotoxic and memory CD8+ T cell responses

Bacterial phagocytosis and antigen cross-presentation to activate CD8⁺ T cells are principal functions of professional antigen presenting cells. However, conventional CD4⁺ T cells also capture and kill bacteria from infected dendritic cells in a process termed transphagocytosis (also known as transinfection). Here, we show that transphagocytic T cells present bacterial antigens to naive CD8⁺ T cells, which proliferate and become cytotoxic in response. CD4⁺ T-cell-mediated antigen presentation also occurs in vivo in the course of infection, and induces the generation of central memory CD8⁺ T cells with low PD-1 expression. Moreover, transphagocytic CD4⁺ T cells induce protective anti-tumour immune responses by priming CD8⁺ T cells, highlighting the potential of CD4⁺ T cells as a tool for cancer immunotherapy.

Antigen presentation is generally considered the domain of innate immune cells, but CD4⁺ T cells can transphagocytose bacteria from infected dendritic cells. Here the authors show CD4⁺ T cells can transphagocytose bacterial and tumour antigens and present them to CD8⁺ T cells to activate memory and cytotoxic functions.

Human mast cells present antigen to autologous CD4+ T cells

BACKGROUND

Mast cells (MCs), the primary effector cell of the atopic response, participate in immune defense at host/environment interfaces, yet the mechanisms by which they interact with CD4⁺ T cells has been controversial.

OBJECTIVE

We used in situ-matured primary human MCs and matched CD4⁺ T cells to diligently assess the ability of MCs to act as antigen-presenting cells.

METHODS

We examined mature human skin-derived MCs using flow cytometry for expression of antigen-presenting molecules, for their ability to stimulate CD4⁺ T cells to express CD25 and proliferate when exposed to superantigen or to cytomegalovirus (CMV) antigen using matched T cells and MCs from CMV-seropositive or CMV-seronegative donors, and for antigen uptake. Subcellular localization of antigen, HLA molecules, and tryptase was analyzed by using structured illumination microscopy.

RESULTS

Our data show that IFN-γ induces HLA class II, HLA-DM, CD80, and CD40 expression on MCs, whereas MCs take up soluble and particulate antigens in an IFN-γ-independent manner. IFN-γ-primed MCs guide activation of T cells by Staphylococcus aureus superantigen and, when preincubated with CMV antigens, induce a recall CD4⁺ T_H1 proliferation response only in CMV-seropositive donors. MCs co-opt their secretory granules for antigen processing and presentation. Consequently, MC degranulation increases surface delivery of HLA class II/peptide, further enhancing stimulation of T-cell proliferation.

CONCLUSIONS

IFN-γ primes human MCs to activate T cells through superantigen and to present CMV antigen to T_H1 cells, co-opting MC secretory granules for antigen processing and presentation and creating a feed-forward loop of T-cell-MC cross-activation.

Dual activation of Toll-like receptors 7 and 9 impairs the efficacy of antitumor vaccines in murine models of metastatic breast cancer

PURPOSE

Since combination of Toll-like receptor (TLR) ligands could boost antitumor immunity, we evaluated the efficacy of dendritic cell (DC) vaccines upon dual activation of TLR9 and TLR7 in breast cancer models.

METHODS

DCs were generated from mouse bone marrow or peripheral blood from healthy human donors and stimulated with CpG1826 (mouse TLR9 agonist), CpG2006 or IMT504 (human TLR9 agonists) and R848 (TLR7 agonist). Efficacy of antitumor vaccines was evaluated in BALB/c mice bearing metastatic mammary adenocarcinomas.

RESULTS

CpG-DCs improved the survival of tumor-bearing mice, reduced the development of lung metastases and generated immunological memory. However, dual activation of TLRs impaired the efficacy of DC vaccines. In vitro, we found that R848 inhibited CpG-mediated maturation of murine DCs. A positive feedback loop in TLR9 mRNA expression was observed upon CpG stimulation that was inhibited in the presence of R848. Impaired activation of NF-κB was detected when TLR9 and TLR7 were simultaneously activated. Blockade of nitric oxide synthase (NOS) and indoleamine-pyrrole-2,3-dioxygenase (IDO) improved the activation of CpG-DCs. When we evaluated the effect of combined activation of TLR9 and TLR7 in human DCs, we found that R848 induced robust DC activation that was inhibited by TLR9 agonists.

CONCLUSIONS

These observations provide insight in the biology of TLR9 and TLR7 crosstalk and suggest caution in the selection of agonists for multiple TLR stimulation. Blockade of NOS and IDO could improve the maturation of antitumor DC vaccines. R848 could prove a useful adjuvant for DC vaccines in human patients.

Distinctive role of efferocytosis in dendritic cell maturation and migration in sterile or infectious conditions

Efferocytosis, or clearance of apoptotic cells (ACs), by dendritic cells (DCs) leads to immune response suppression and tolerance to self-antigens. However, efferocytosis of infected apoptotic cells (IACs) leads to the production of a mixed pro- and anti-inflammatory cytokine milieu. We examined the DC phenotype and ability to migrate after phagocytosis of ACs or IACs and observed higher levels of CD86 and CCR7 expression in DCs, as well as enhanced migration capacity following efferocytosis of IACs. Interestingly, higher levels of interleukin-1β, interleukin-10 and prostaglandin E₂ (PGE₂ ) were also produced in this context. Blockage of IAC recognition led to an impaired maturation profile and PGE₂ production, which may have contributed to reduced CD86 and CCR7 expression and migration capacity. These data contribute to the understanding of how efferocytosis of sterile or infected cells may regulate the adaptive immune response, although the precise role of PGE₂ in this process requires further investigation.

Kluyveromyces marxianus and Saccharomyces boulardii Induce Distinct Levels of Dendritic Cell Cytokine Secretion and Significantly Different T Cell Responses In Vitro

Interactions between members of the intestinal microbiota and the mucosal immune system can significantly impact human health, and in this context, fungi and food-related yeasts are known to influence intestinal inflammation through direct interactions with specialized immune cells in vivo. The aim of the present study was to characterize the immune modulating properties of the food-related yeast Kluyveromyces marxianus in terms of adaptive immune responses indicating inflammation versus tolerance and to explore the mechanisms behind the observed responses. Benchmarking against a Saccharomyces boulardii strain with probiotic effects documented in clinical trials, we evaluated the ability of K. marxianus to modulate human dendritic cell (DC) function in vitro. Further, we assessed yeast induced DC modulation of naive T cells toward effector responses dominated by secretion of IFNγ and IL-17 versus induction of a T_reg response characterized by robust IL-10 secretion. In addition, we blocked relevant DC surface receptors and investigated the stimulating properties of β-glucan containing yeast cell wall extracts. K. marxianus and S. boulardii induced distinct levels of DC cytokine secretion, primarily driven by Dectin-1 recognition of β-glucan components in their cell walls. Upon co-incubation of yeast exposed DCs and naive T cells, S. boulardii induced a potent IFNγ response indicating T_H1 mobilization. In contrast, K. marxianus induced a response dominated by Foxp3⁺ T_reg cells, a characteristic that may benefit human health in conditions characterized by excessive inflammation and positions K. marxianus as a strong candidate for further development as a novel yeast probiotic.

Recombinant human lactoferrin modulates human PBMC derived macrophage responses to BCG and LPS

Lactoferrin, an iron-binding glycoprotein found in mammalian mucosal secretions and granules of neutrophils, possesses several immune modulatory properties. Published reports indicate that lactoferrin enhances the efficacy of the tuberculosis vaccine, BCG (Bacillus Calmette Guerin), both by increasing macrophage and dendritic cell ability to stimulate receptive T cells and by modulating the inflammatory response. This report is the first to demonstrate the effects of a recombinant human lactoferrin (10 μg/mL) on human PBMC derived CD14⁺ and CD16⁺ macrophages stimulated with a strong (LPS, 10 ng/mL) or weaker (BCG, MOI 1:1) stimulator of inflammation. After 3 days culture, LPS and human lactoferrin treated CD14⁺ cells significantly increased production of IL-10, IL-6, and MCP-1 compared to the LPS only group. In contrast, similarly treated CD16⁺ macrophages increased production of IL-12p40 and IL-10 and decreased TNF-α. Limited changes were observed in BCG stimulated CD14⁺ and CD16⁺ macrophages with and without lactoferrin. Analysis of surface expression of antigen presentation and co-stimulatory molecules demonstrated that CD14⁺ macrophages, when stimulated with BCG or LPS and cultured with lactoferrin, increased expression of CD86. CD16⁺ macrophages treated with lactoferrin showed a similar trend of increase in CD86 expression, but only when stimulated with BCG.

Immunomodulation of human intestinal T cells by the synthetic CD80 antagonist RhuDex®

Deregulated activation of mucosal lamina propria T cells plays a central role in the pathogenesis of intestinal inflammation. One of the means to attenuate T cell activation is by blocking the CD28/CD80 co-stimulatory pathway. Here we investigate RhuDex®, a small molecule that binds to human CD80, for its effects on the activation of lamina propria T cells employing a gut-culture model of inflammation. To this end, lamina propria leukocytes (LPL) and peripheral blood lymphocytes (PBL) were stimulated either through the CD3/T-cell-receptor complex or the CD2-receptor (CD2) employing agonistic monoclonal antibodies. Co-stimulatory signals were provided by CD80/CD86 present on lamina propria myeloid cells or LPS-activated peripheral blood monocytes. Results show that RhuDex® caused a profound reduction of LPL and PBL proliferation, while Abatacept (CTLA-4-Ig) inhibited LPL proliferation to a small degree, and had no effect on PBL proliferation. Furthermore, Abatacept significantly inhibited IL-2, TNF-α, and IFN-γ release from LPL, primarily produced by CD4⁺ T cells, where IL-2 blockage was surprisingly strong, suggesting a down-regulating effect on regulatory T cells. In contrast, in the presence of RhuDex®, secretion of IL-17, again mostly by CD4⁺ T cells, and IFN-γ was inhibited in LPL and PBL, yet IL-2 remained unaffected. Thus, RhuDex® efficiently inhibited lamina propria and peripheral blood T-cell activation in this pre-clinical study making it a promising drug candidate for the treatment of intestinal inflammation.

B cells in teleost fish act as pivotal initiating APCs in priming adaptive immunity: an evolutionary perspective on the origin of the B-1 cell subset and B7 molecules

The long-held paradigm that B cells cannot uptake nonspecific particulate Ags for the initiation of primary adaptive immunity has been challenged by the recent discovery that teleost B cells have potent phagocytic and microbicidal abilities. This discovery provides preliminary clues that primitive B cells might act as initiating APCs in priming adaptive immunity. In this study, zebrafish B cells clearly showed a potent Ag-presenting ability to both soluble Ags and bacterial particles to prime naive CD4(+) T cell activation. This finding demonstrates the innate-like nature of teleost B cells in the interface of innate and adaptive immunity, indicating that they might consist of a major population of initiating APCs whose performance is similar to that of dendritic cells. Given the functional similarities between teleost B cells and the mammalian B-1 subset, we hypothesize that B-1 lineage and teleost B cells might originate from a common ancestor with potent phagocytic and initiating APC capacities. In addition, CD80/86 and CD83 costimulatory signals were identified as being essential for B cell-initiated adaptive immunity. This result suggests that the costimulatory mechanism originated as early as the origin of adaptive immunity and is conserved throughout vertebrate evolution. In fish, only a single CD80/86 copy exists, which is similar to mammalian CD86 rather than to CD80. Thus, CD86 might be a more primordial B7 family member that originated from fish. This study provides valuable insights into the evolutionary history of professional APCs, B cell lineages, and the costimulatory mechanism underlying adaptive immunity as a whole.

Expression of CD80 on cultured neonatal mice cardiomyocytes and attenuation of cytotoxic T lymphocyte-mediated lysis

Transplantation of cultured heterogeneous proliferating cardiomyocytes is a promising therapeutic approach for the treatment of the damage cardiac area resulting from myocardial infarction. However, the chances of recipient rejection are high. How to reduce the immunogenicity of heterogeneous cardiomyocytes and attenuate immune rejection is one of the key stumbling blocks in the application of these cells. In this study, we determined that cultured neonatal cardiomyocytes from mice can express CD80 after culture. CD80 is one of the key costimulatory molecules. Most scholars believe that the main function of CD80 is to activate and boost immune rejection. However, recent studies have shown that CD80 may primarily bind with CTLA-4 and inhibit the immune response. To further study how CD80 worked on these cells, a cytotoxic T-lymphocyte (CTL) assay was performed. The results showed that activated allogenic CTLs lysed cultured cardiomyocytes lacking CD80 expression, but they did not efficiently lyse cardiomyocytes expressing CD80. If we blocked the CD80 with anti-CD80 monoclonal antibody (mAb), the percentages of cardiomyocytes lysis were significantly increased. CD80 can bind CD28, CTLA-4, PD-L1, and even B7-H1, but the main ligands are CD28 and CTLA-4. Thus, we blocked the two ligands separately. When anti-CTLA-4 mAb was applied, the percentages of cardiomyocytes lysis were significantly increased, but when anti-CD28 mAb was applied, the percentages of cell lysis were the same as the intact control. The results indicated that CD80 and CTLA-4 played an important role on the attenuation of CTL-mediated lysis. To our knowledge, this study, for the first time, proves that cardiomyocytes can express CD80 and this expression pattern can resist CTL-mediated lysis through CTLA-4 pathway. The results could have implications in efforts to improve therapeutic strategies for cardiomyocyte transplantation.

Particulate formulations for the delivery of poly(I:C) as vaccine adjuvant

Current research and development of antigens for vaccination often center on purified recombinant proteins, viral subunits, synthetic oligopeptides or oligosaccharides, most of them suffering from being poorly immunogenic and subject to degradation. Hence, they call for efficient delivery systems and potent immunostimulants, jointly denoted as adjuvants. Particulate delivery systems like emulsions, liposomes, nanoparticles and microspheres may provide protection from degradation and facilitate the co-formulation of both the antigen and the immunostimulant. Synthetic double-stranded (ds) RNA, such as polyriboinosinic acid-polyribocytidylic acid, poly(I:C), is a mimic of viral dsRNA and, as such, a promising immunostimulant candidate for vaccines directed against intracellular pathogens. Poly(I:C) signaling is primarily dependent on Toll-like receptor 3 (TLR3), and on melanoma differentiation-associated gene-5 (MDA-5), and strongly drives cell-mediated immunity and a potent type I interferon response. However, stability and toxicity issues so far prevented the clinical application of dsRNAs as they undergo rapid enzymatic degradation and bear the potential to trigger undue immune stimulation as well as autoimmune disorders. This review addresses these concerns and suggests strategies to improve the safety and efficacy of immunostimulatory dsRNA formulations. The focus is on technological means required to lower the necessary dosage of poly(I:C), to target surface-modified microspheres passively or actively to antigen-presenting cells (APCs), to control their interaction with non-professional phagocytes and to modulate the resulting cytokine secretion profile.

Graft-versus-host disease: part I. Pathogenesis and clinical manifestations of graft-versus-host disease

Approximately 25,000 allogeneic hematopoietic cell transplants are performed worldwide each year for a variety of malignant and non-malignant conditions. Graft-versus-host disease represents one of the most frequent complications and is a major source of long-term morbidity and mortality. Whereas acute graft-versus-host disease is induced by recognition of host tissues as foreign by immunocompetent donor cells, the pathogenesis of chronic graft-versus-host disease is not as well understood, and continues to be a major treatment challenge. Part I of this two-part series reviews the epidemiologic factors, classification, pathogenesis, and clinical manifestations of acute and chronic graft-versus-host disease. Part II discusses the topical, physical, and systemic treatment options available to patients with graft-versus-host disease.

A fiber-modified adenoviral vector interacts with immunoevasion molecules of the B7 family at the surface of murine leukemia cells derived from dormant tumors

Tumor cells can escape the immune system by overexpressing molecules of the B7 family, e.g. B7-H1 (PD-L1 or CD86), which suppresses the anti-tumor T-cell responses through binding to the PD-1 receptor, and similarly for B7.1 (CD80), through binding to CTLA-4. Moreover, direct interactions between B7-H1 and B7.1 molecules are also likely to participate in the immunoevasion mechanism. In this study, we used a mouse model of tumor dormancy, DA1-3b leukemia cells. We previously showed that a minor population of DA1-3b cells persists in equilibrium with the immune system for long periods of time, and that the levels of surface expression of B7-H1 and B7.1 molecules correlates with the dormancy time. We found that leukemia cells DA1-3b/d365 cells, which derived from long-term dormant tumors and overexpressed B7-H1 and B7.1 molecules, were highly permissive to Ad5FB4, a human adenovirus serotype 5 (Ad5) vector pseudotyped with chimeric human-bovine fibers. Both B7-H1 and B7.1 were required for Ad5FB4-cell binding and entry, since (i) siRNA silencing of one or the other B7 gene transcript resulted in a net decrease in the cell binding and Ad5FB4-mediated transduction of DA1-3b/d365; and (ii) plasmid-directed expression of B7.1 and B7-H1 proteins conferred to Ad5FB4-refractory human cells a full permissiveness to this vector. Binding data and flow cytometry analysis suggested that B7.1 and B7-H1 molecules played different roles in Ad5FB4-mediated transduction of DA1-3b/d365, with B7.1 involved in cell attachment of Ad5FB4, and B7-H1 in Ad5FB4 internalization. BRET analysis showed that B7.1 and B7-H1 formed heterodimeric complexes at the cell surface, and that Ad5FB4 penton, the viral capsomere carrying the fiber projection, could negatively interfere with the formation of B7.1/B7-H1 heterodimers, or modify their conformation. As interactors of B7-H1/B7.1 molecules, Ad5FB4 particles and/or their penton capsomeres represent potential therapeutic agents targeting cancer cells that had developed immunoevasion mechanisms.

JNK1, but not JNK2, is required in two mechanistically distinct models of inflammatory arthritis

The roles of the c-Jun N-terminal kinases (JNKs) in inflammatory arthritis have been investigated; however, the roles of each isotype (ie, JNK1 and JNK2) in rheumatoid arthritis and conclusions about whether inhibition of one or both is necessary for amelioration of disease are unclear. By using JNK1- or JNK2-deficient mice in the collagen-induced arthritis and the KRN T-cell receptor transgenic mouse on C57BL/6 nonobese diabetic (K/BxN) serum transfer arthritis models, we demonstrate that JNK1 deficiency results in protection from arthritis, as judged by clinical score and histological evaluation in both models of inflammatory arthritis. In contrast, abrogation of JNK2 exacerbates disease. In collagen-induced arthritis, the distinct roles of the JNK isotypes can, at least in part, be explained by altered regulation of CD86 expression in JNK1- or JNK2-deficient macrophages in response to microbial products, thereby affecting T-cell-mediated immunity. The protection from K/BxN serum-induced arthritis in Jnk1(-/-) mice can also be explained by inept macrophage function because adoptive transfer of wild-type macrophages to Jnk1(-/-) mice restored disease susceptibility. Thus, our results provide a possible explanation for the modest therapeutic effects of broad JNK inhibitors and suggest that future therapies should selectively target the JNK1 isoform.

Murine models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disorder. The study of diverse mouse models of lupus has provided clues to the etiology of SLE. Spontaneous mouse models of lupus have led to identification of numerous susceptibility loci from which several candidate genes have emerged. Meanwhile, induced models of lupus have provided insight into the role of environmental factors in lupus pathogenesis as well as provided a better understanding of cellular mechanisms involved in the onset and progression of disease. The SLE-like phenotypes present in these models have also served to screen numerous potential SLE therapies. Due to the complex nature of SLE, it is necessary to understand the effect specific targeted therapies have on immune homeostasis. Furthermore, knowledge gained from mouse models will provide novel therapy targets for the treatment of SLE.

Decreased numbers of peripheral blood dendritic cells in patients with coronary artery disease are associated with diminished plasma Flt3 ligand levels and impaired plasmacytoid dendritic cell function

We investigated whether activation of circulating DCs (dendritic cells) or levels of Flt3L (FMS-like tyrosine kinase 3 ligand) and GM-CSF (granulocyte/macrophage colony-stimulating factor), haematopoietic growth factors important for DC differentiation, could account for reduced blood DC numbers in CAD (coronary artery disease) patients. Concentrations of Flt3L and GM-CSF were measured in plasma from CAD patients (n = 15) and controls (n = 12). Frequency and phenotype of mDCs (myeloid dendritic cells) and pDCs (plasmacytoid dendritic cells) were analysed by multicolour flow cytometry in fresh blood, and after overnight incubation with TLR (Toll-like receptor)-4 or -7 ligands LPS (lipopolysaccharide) or IQ (imiquimod). DC function was measured by IL (interleukin)-12 and IFN (interferon)-α secretion. Circulating numbers of CD11c+ mDCs and CD123+ pDCs and frequencies of CD86+ and CCR-7+ (CC chemokine receptor type 7) mDCs, but not pDCs, were declined in CAD. In addition, plasma Flt3L, but not GM-CSF, was lower in patients and positively correlated with blood DC counts. In response to LPS, mDCs up-regulated CD83 and CD86, but CCR-7 expression and IL-12 secretion remained unchanged, similarly in patients and controls. Conversely, pDCs from patients had lower CD83 and CCR-7 expression after overnight incubation and had a weaker IQ-induced up-regulation of CD83 and IFN-α secretion. In conclusion, our results suggest that reduced blood DC counts in CAD are, at least partly, due to impaired DC differentiation from bone marrow progenitors. Decreased levels of mDCs are presumably also explained by activation and subsequent migration to atherosclerotic plaques or lymph nodes. Although mDCs are functioning normally, pDCs from patients appeared to be both numerically and functionally impaired.

Enhancement of suboptimal CD8 cytotoxic T cell effector function in vivo using antigen-specific CD80 defective T cells

T cell upregulation of B7 molecules CD80 and CD86 limits T cell expansion in immunodeficient hosts; however, the relative roles of CD80 separate from CD86 on CD4 versus CD8 T cells in a normal immune system are not clear. To address this question, we used the parent-into-F1 (P→F1) murine model of graft-versus-host disease and transferred optimal and suboptimal doses of CD80 and/or CD86 knockout (KO) T cells into normal F1 hosts. Enhanced elimination of host B cells by KO T cells was observed only at suboptimal donor cell doses and was greatest for CD80 KO→F1 mice. Wild-type donor cells exhibited peak CD80 upregulation at day 10; CD80 KO donor cells exhibited greater peak (day 10) donor T cell proliferation and CD8 T cell effector CTL numbers versus wild-type→F1 mice. Fas or programmed cell death-1 upregulation was normal as was homeostatic contraction of CD80 KO donor cells from days 12-14. Mixing studies demonstrated that maximal host cell elimination was seen when both CD4 and CD8 T cells were CD80 deficient. These results indicate an important role for CD80 upregulation on Ag-activated CD4 and CD8 T cells in limiting expansion of CD8 CTL effectors as part of a normal immune response. Our results support further studies of therapeutic targeting of CD80 in conditions characterized by suboptimal CD8 effector responses.

Advances in lupus stemming from the parent-into-F1 model

The parent-into-F1 model has led to important advances in our understanding of lupus. Here, we review the work in murine lupus that elucidated the role of T cells and supported the conclusion that the parent-into-F1 model of induced lupus compares favorably with de facto gold standard spontaneous models of lupus. Then we focus on recent work in parent-into-F1 mice, which has yielded novel insights into unresolved controversies, such as the role of apoptosis in the pathogenesis of lupus and lupus in patients receiving TNF blockade. Finally, the review considers the evidence that supports a potential role for CD8 T cells, both cytotoxic and memory cells, in mediating disease remission.

Lactoferrin modulation of BCG-infected dendritic cell functions

Lactoferrin, an 80-kDa iron-binding protein with immune modulating properties, is a unique adjuvant component able to enhance efficacy of the existing Mycobacterium bovis Bacillus Calmette Guerin (BCG) vaccine to protect against murine model of tuberculosis. Although identified as having effects on macrophage presentation events, lactoferrin's capability to modulate dendritic cells (DCs) function when loaded with BCG antigens has not been previously recognized. In this study, the potential of lactoferrin to modulate surface expression of MHC II, CD80, CD86 and CD40 from bone marrow-derived dendritic cells (BMDCs) was examined. Generally, lactoferrin decreased pro-inflammatory cytokines [tumor necrosis factor (TNF)-alpha, IL-6 and IL-12p40] and chemokines [macrophage inflammatory protein (MIP)-1alpha and MIP-2] and increased regulatory cytokine, transforming growth factor-beta1 and a T-cell chemotatic factor, monocyte chemotactic protein-1, from uninfected or BCG-infected BMDCs. Culturing BCG-infected BMDCs with lactoferrin also enhanced their ability to respond to IFN-gamma activation through up-regulation of maturation markers: MHC I, MHC II and the ratio of CD86:CD80 surface expression. Furthermore, lactoferrin-exposed BCG-infected DCs increased stimulation of BCG-specific CD3(+)CD4(+) splenocytes, as defined by increasing IFN-gamma production. Finally, BCG-/lactoferrin-vaccinated mice possessed an increased pool of BCG antigen-specific IFN-gamma producing CD3(+)CD4(+)CD62L(-) splenocytes. These studies suggest a mechanism in which lactoferrin may exert adjuvant activity by enhancing DC function to promote generation of antigen-specific T cells.

Targeted NF-kappaB inhibition of asthmatic serum-mediated human monocyte-derived dendritic cell differentiation in a transendothelial trafficking model

Transendothelial trafficking model mimics in vivo differentiation of monocytes into dendritic cells (DC). The serum from patients with systemic lupus erythematosus promotes the differentiation of monocytes into mature DC. We have shown that selective inhibition of NF-kappaB by adenoviral gene transfer of a novel mutated IkappaBalpha (AdIkappaBalphaM) in DC contributes to T cell tolerance. Here we demonstrated for the first time that asthmatic serum facilitated human monocyte-derived DC (MDDC) maturation associated with increased NF-kappaB activation in this model. Furthermore, selective blockade of NF-kappaB by AdIkappaBalphaM in MDDC led to increased apoptosis, and decreased levels of CD80, CD83, CD86, and IL-12 p70 but not IL-10 in asthmatic serum-stimulated MDDC, accompanied by reduced proliferation of T cells. These results suggest that AdIkappaBalphaM-transferred MDDC are at a more immature stage which is beneficial to augment the immune tolerance in asthma.

Rat cytomegalovirus infection depletes MHC II in bone marrow derived dendritic cells

While cytomegalovirus (CMV) infects and replicates in a multitude of cell types, the ability of the virus to replicate in antigen presenting cells (APCs) is believed to play a critical role in the viral dissemination and latency. CMV infection of APCs and manipulation of their function are important areas of investigation. CMV down regulation of MHC II is reportedly mediated by the HCMV proteins US2, US3, UL83, UL111a (vIL10) or through the induction of cellular IL10. In this study, we demonstrate that rat CMV (RCMV) significantly reduces MHC II expression neither by mechanisms that do not involve orthologues of the known HCMV genes nor by an increase in cellular IL10. Rat bone marrow derived dendritic cells (BMDC) were highly susceptible to infection with RCMV and a recombinant RCMV expressing eGFP. RCMV infection of BMDCs depleted both surface and intracellular MHC II to nearly undetectable levels as well as reduced surface expression of MHC I. The effect on MHC II only occurred in the infected GFP positive cells and is mediated by an immediate early or early viral gene product. Furthermore, treatment of uninfected immature DCs with virus-free conditioned supernatants from infected cells failed to down regulate MHC II. RCMV depletion of MHC II was sensitive to treatment with lysosomal inhibitors but not proteasomal inhibitors suggesting that the mechanism of RCMV-mediated down regulation of MHC II occurs through endocytic degradation. Since RCMV does not encode homologues of US2, US3, UL83 or UL111a, these data indicate a novel mechanism for RCMV depletion of MHC II.

B7-1 induces immunosuppression when expressed in cultured neonatal mice keratinocytes

BACKGROUND

Chimeric (allo-auto or even xeno-auto) cultured keratinocyte grafting did not exhibit obvious acute rejection or chronic rejection. Although cultured murine keratinocytes were recognized by allogenic CD8+ T cells, they were not rejected. The precise mechanisms underlying this process were unclear. To analyze how keratinocytes attenuated the immune response, we investigated the effect of culturing on neonatal murine keratinocytes and their immunomodulatory properties.

METHODS

Keratinocytes isolated and purified from BALB/c and C57BL/6 neonatal mice were cultured for 7 days. The expression of B7-1, B7-2, B7-H1 and MHC-I was examined by semi-quantitative RT polymerase chain reaction (PCR), fluorescence microscopy and flow cytometry. Cytotoxicity and mixed lymphocyte response (MLR) assays were performed to determine the effects of keratinocytes on cytotoxic T-lymphocyte (CTL) mediated cell lysis and lymphocyte proliferation.

RESULTS

B7-1 was highly expressed in cultured, proliferating murine keratinocytes while no expression of B7-2 and B7-H1 was found. Keratinocytes that expressed B7-1 decreased CTL-mediated cell lysis by an interaction between B7-1 and CTLA-4. In addition, autologous keratinocytes but not allogeneic keratinocytes significantly suppressed auto-specific lymphocyte proliferation in a dose-dependent manner. The modulation was dependent on B7-1 expression and its interaction with CTLA-4.

CONCLUSIONS

Cultured murine keratinocytes expressed B7-1, but not B7-2 or B7-H1. The keratinocytes attenuated CTL-mediated lysis and suppressed lymphocyte proliferation via an interaction with B7-1 and CTLA-4. Therefore, separate expression of B7-1 induced immunosuppression. Non-professional APCs (antigen presenting cells) which separately express B7-1 may possess an ability to induce immunotolerance and thus act as a regulatory APC.

Repeated social defeat activates dendritic cells and enhances Toll-like receptor dependent cytokine secretion

Stress hormones significantly impact dendritic cell (DC) activation and function, typically in a suppressive fashion. However, a social stressor termed social disruption (SDR) has been shown to induce an increase in inflammatory responses and a state of glucocorticoid resistance in splenic CD11b+ monocytes. These experiments were designed to determine the effects of SDR on DC activation, Toll-like receptor-induced cytokine secretion, and glucocorticoid sensitivity. Compared to cells obtained from control animals, splenic DCs from SDR mice displayed increased levels of MHC I, CD80, and CD44, indicative of an activated phenotype. In addition, DCs from SDR mice produced comparatively higher TNF-alpha, IL-6, and IL-10 in response to in vitro stimulation with LPS and CpG DNA. Increased amounts of TNF-alpha and IL-6 were also evident in SDR DC cultures stimulated with poly(I:C). Furthermore, as shown previously in CD11b+ monocytes, the CD11c+ DCs obtained from SDR mice were glucocorticoid resistant. Taken together, the data suggest that social stress, in the absence of any immune challenge, activates DCs, increases DC cytokine secretion in response to Toll-specific stimuli and renders DCs glucocorticoid resistant.

Immune responses in patients with metal-on-metal hip articulations: a long-term follow-up

Metal-on-metal (MoM) hip bearings are being inserted into ever-younger patients. The effects on the immune system of chronic exposure are unknown. We investigated the immune response of patients with MoM hip bearings. In patients with MoM implants, the expression of antigen-presenting cell (APC) surface molecules (CD86 and HLA-DR) was seen to be significantly higher (P < .05) than control group. High levels of APC surface molecules suggest an activated state and attempts to propagate an immune response. However, in the same group, the expression of T-cell markers (CD3 and CD28) was low, indicating a small T-cell population. This suggests, despite the activation of APCs, that T cells down-regulate immune responses in MoM articulations. Conversely, in metal-on-polyethylene articulations, expression of T-cell molecules was elevated and expression of APC molecules lowered.

Therapeutic potential of CD8+ cytotoxic T lymphocytes in SLE

Recent evidence supports the idea that following a break in tolerance, CD8 cytotoxic T lymphocytes (CTL) may be an important but unrecognized mechanism for limiting expansion of autoreactive B cells. Failure of this mechanism could allow persistence of CD4 T cell driven polyclonal B cell activation resulting in clinical lupus. Although CD8 CTL failure may occur early in disease, work in mice supports the concept that therapeutic CTL enhancement may be both practical and beneficial in lupus. Devising such therapy for humans will first require an understanding of the in vivo mechanisms critical in CTL expansion and down regulation, particularly in the lupus setting which may differ from CTL generation in other clinical settings (e.g. tumors, infections).

CTL-promoting effects of CD40 stimulation outweigh B cell-stimulatory effects resulting in B cell elimination and disease improvement in a murine model of lupus

CD40/CD40L signaling promotes both B cell and CTL responses in vivo, the latter being beneficial in tumor models. Because CTL may also limit autoreactive B cell expansion in lupus, we asked whether an agonist CD40 mAb would exacerbate lupus due to B cell stimulation or would improve lupus due to CTL promotion. These studies used an induced model of lupus, the parent-into-F1 model in which transfer of DBA/2 splenocytes into B6D2F1 mice induces chronic lupus-like graft-vs-host disease (GVHD). Although agonist CD40 mAb treatment of DBA-->F1 mice initially exacerbated B cell expansion, it also strongly promoted donor CD8 T cell engraftment and cytolytic activity such that by 10 days host B cells were eliminated consistent with an accelerated acute GVHD. CD40 stimulation bypassed the requirement for CD4 T cell help for CD8 CTL possibly by licensing dendritic cells (DC) as shown by the following: 1) greater initial activation of donor CD8 T cells, but not CD4 T cells; 2) earlier activation of host DC; 3) host DC expansion that was CD8 dependent and CD4 independent; and 4) induction of acute GVHD using CD4-depleted purified DBA CD8+ T cells. A single dose of CD40 mAb improved lupus-like renal disease at 12 wk, but may not suffice for longer periods consistent with a need for continuing CD8 CTL surveillance. These results demonstrate that in the setting of lupus-like CD4 T cell-driven B cell hyperactivity, CTL promotion is both feasible and beneficial and the CTL-promoting properties of CD40 stimulation outweigh the B cell-stimulatory properties.

Preferential costimulation by CD80 results in IL-10-dependent TGF-beta1(+) -adaptive regulatory T cell generation

Costimulatory ligands CD80 and CD86 have different binding preferences and affinities to their receptors, CD28 and CTLA-4. Earlier, we demonstrated that CD80 binds to CTLA-4 with higher affinity and has a role in suppressing T cell response. The current study demonstrates that not only did blockade of CD86 upon Ag presentation by bone marrow-derived dendritic cells (DC) to OVA-specific T cells result in induction of hyporesponsive T cells but also that these T cells could suppress the proliferative response of effector T cells. These T cells showed TGF-beta1 on their surface and secreted TGF-beta1 and IL-10 upon restimulation. Although blockade of CTLA-4 and neutralization of IL-10 profoundly inhibited the induction of these TGF-beta1(+) T cells, their ability to suppress the effector T cell proliferation was abrogated by neutralization of TGF-beta1 alone. Induction of TGF-beta1(+) and IL-10(+) T cells was found to be independent of natural CD4(+)CD25(+) regulatory T cells, demonstrating that preferential ligation of CTLA-4 by CD80 induced IL-10 production by effector T cells, which in turn promoted the secretion of TGF-beta1. Treatment of prediabetic NOD mice with islet beta cell Ag-pulsed CD86(-/-) DCs, but not CD80(-/-) DCs, resulted in the induction of TGF-beta1- and IL-10-producing cells, significant suppression of insulitis, and delay of the onset of hyperglycemia. These observations demonstrate not only that CD80 preferentially binds to CTLA-4 but also that interaction during Ag presentation can result in IL-10-dependent TGF-beta1(+) regulatory T cell induction, reinstating the potential of approaches to preferentially engage CTLA-4 through CD80 during self-Ag presentation in suppressing autoimmunity.

Graded function of CD80 and CD86 in initiation of T-cell immune response and cardiac allograft survival

CD28 and cytotoxic T-lymphocyte antigen-4 (CTLA-4), which have opposing functions in T-cell responses, share the two ligands, CD80 (B7-1) and CD86 (B7-2). To understand the functions of CD80 and CD86, respectively, CD80(low) dendritic cells (DCs) and CD86(low) DCs were prepared by using RNA interference. Then CD80 and CD86 functions were analysed by in vitro mixed lymphocyte reaction and cytokine production assay. Effect on cardiac allograft survival was assayed in vivo. In this study, graded stimulatory function of CD80 and CD86, stronger inhibition of proliferation, and stronger prolongation of transplant survival were observed when CD80 and CD86 were blocked simultaneously.

Administration of dendritic cells modified by RNA interference prolongs cardiac allograft survival

Systemic administration of immature donor-dendritic cells (DC) that are deficient in co-stimulatory molecules delays the onset of allograft rejection. However, it is not easy to control culture condition and guarantee that the administered DC are in the immature stages, which obviously affects their therapeutic effect. In this study, we attempted to inhibit expression of CD86 on DC using an RNA interference technology. The function of CD86(low) DC was determined by the influence on their capacity to stimulate T cell proliferation and by the effect of DC systemic administration on survival of cardiac allografts. CD86(low) DC stimulated low T cell proliferative responses in vitro and administration of CD86(low) DC prolonged survival of heart allografts in vivo. These results suggest that RNA interference is a useful approach to modify DC function, which has potentials for clinical application.

Sulfamethoxazole and its metabolite nitroso sulfamethoxazole stimulate dendritic cell costimulatory signaling

Different signals in addition to the antigenic signal are required to initiate an immunological reaction. In the context of sulfamethoxazole allergy, the Ag is thought to be derived from its toxic nitroso metabolite, but little is known about the costimulatory signals, including those associated with dendritic cell maturation. In this study, we demonstrate increased CD40 expression, but not CD80, CD83, or CD86, with dendritic cell surfaces exposed to sulfamethoxazole (250-500 microM) and the protein-reactive metabolite nitroso sulfamethoxazole (1-10 microM). Increased CD40 expression was not associated with apoptosis or necrosis, or glutathione depletion. Covalently modified intracellular proteins were detected when sulfamethoxazole was incubated with dendritic cells. Importantly, the enzyme inhibitor 1-aminobenzotriazole prevented the increase in CD40 expression with sulfamethoxazole, but not with nitroso sulfamethoxazole or LPS. The enzymes CYP2C9, CYP2C8, and myeloperoxidase catalyzed the conversion of sulfamethoxazole to sulfamethoxazole hydroxylamine. Myeloperoxidase was expressed at high levels in dendritic cells. Nitroso sulfamethoxazole immunogenicity was inhibited in mice with a blocking anti-CD40L Ab. In addition, when a primary nitroso sulfamethoxazole-specific T cell response using drug-naive human cells was generated, the magnitude of the response was enhanced when cultures were exposed to a stimulatory anti-CD40 Ab. Finally, increased CD40 expression was 5-fold higher on nitroso sulfamethoxazole-treated dendritic cells from an HIV-positive allergic patient compared with volunteers. These data provide evidence of a link between localized metabolism, dendritic cell activation, and drug immunogenicity.

Unexpected role of B and T lymphocyte attenuator in sustaining cell survival during chronic allostimulation

B and T lymphocyte attenuator (BTLA; CD272) can deliver inhibitory signals to B and T cells upon binding its ligand herpesvirus entry mediator. Because CD28, CTLA-4, programmed death-1, and ICOS regulate the development of acute graft-vs-host disease (GVHD), we wished to assess if BTLA also played a role in this T cell-mediated response. In the nonirradiated parental-into-F1 model of acute GVHD, BTLA+/+ and BTLA-/- donor lymphocytes showed equivalent engraftment and expansion during the first week of the alloresponse. Unexpectedly, BTLA-/- donor T cells failed to sustain GVHD, showing a decline in surviving donor cell numbers beginning at day 9 and greatly reduced by day 11. Similarly, inhibition of BTLA-herpesvirus entry mediator engagement by in vivo administration of a blocking anti-BTLA Ab also caused reduced survival of donor cells. Microarray analysis revealed several genes that were differentially expressed by BTLA-/- and BTLA+/+ donor CD4+ T cells preceding the decline in BTLA-/- donor T cells. Several genes influencing Th cell polarization were differentially expressed by BTLA+/+ and BTLA-/- donor cells. Additionally, the re-expression of the IL-7Ralpha subunit that occurs in BTLA+/+ donor cells after 1 wk of in vivo allostimulation was not observed in BTLA-/- donor CD4+ cells. The striking loss of BTLA-/- T cells in this model indicates a role for BTLA activity in sustaining CD4+ T cell survival under the conditions of chronic stimulation in the nonirradiated parental-into-F1 GVHD.

Cancer vaccines and tumor dormancy: a long-term struggle between host antitumor immunity and persistent cancer cells?

Tumor dormancy is a phenomenon characterized by the persistence of residual cancer cells for long periods in the host. Evidence has emerged that a balance exists between the immune response and dormant tumor cells. This review presents our current understanding of the immune relationship between host and dormant tumor cells and the mechanism developed by these cells to escape host antitumor immunity. Implications of this immune escape for cancer vaccine strategy are considered.

Altered Toll-like receptor 9 responses in circulating B cells at the onset of extensive chronic graft-versus-host disease

B cells appear to play a role in chronic graft-versus-host disease (cGVHD) as shown in murine models and the success of anti-CD20 B cell antibody treatment in humans. Recent studies have shown that immunostimulatory microbial CpG-DNA splenic responses were enhanced in murine GVHD. We hypothesized that CpG-induced B cell responses are increased in human cGVHD. Newly diagnosed cGVHD patients enrolled on the COG protocol ASCT0031 were divided into early (3-8 months postblood and marrow transplant [BMT]) and late (> or =9 months post-BMT) onset groups and compared to time-matched control BMT patients. A significantly greater percentage of phosphorothioate (PS)-modified CpG stimulated B cells from cGVHD patients demonstrated an increased expression of CD86 compared to controls (P = .0004). This response had a significant correlation between B cell TLR9 expression (r(2) = 0.65; P = .002) and CD86 upregulation using the entirely TLR9-dependent native phosphodiester CpG (P = .003). The PS-modified CpG response at 2 months after initiation of cGVHD therapy demonstrated a trend toward predicting therapeutic response at 9 months post-BMT (P = .07). These findings suggest that an increased number of B cells, primed for a TLR9 response, may play a role in the pathophysiology of cGVHD.

Immunomodulation of the Anti-Islet CD8 T Cell Response by B7-2

The absence of diabetes in NOD mice devoid of B7-2 signifies a critical role played by B7-2 in promoting autoimmunity. We asked whether the CD8 T cell compartment is impacted by the absence of B7-2. We found significantly lower expansion of anti-islet CD8 T cells in B7-2KO mice, although their survival and activation states remained unchanged in the pancreatic lymph nodes (PLNs). CD8 T cells from B7-2KO mice exhibited significantly diminished effector function compared to NOD mice. Adoptive transfer experiments using in vitro activated anti-islet CD8 T cells showed that B7-2 does not control the effector phase of the autoreactive CD8 T cell response. Our data indicate that B7-2 promotes pancreatic autoimmunity by controlling CD8 T cell expansion and effector function, but is dispensable for CD8 T cell activation, survival, and the effector phase of anti-islet CD8 T cell response.

Transfection of CD40 in a human oral squamous cell carcinoma keratinocyte line upregulates immune potency and costimulatory molecules

BACKGROUND

There is upregulation of class II molecules of the major histocompatibility complex (MHC) by keratinocytes in oral squamous cell carcinoma (OSCC) and inflammatory diseases such as lichen planus. The significance of this expression, or whether it is accompanied by upregulation of membrane-bound costimulatory molecules, is unknown.

OBJECTIVES

To compare the expression of CD40, CD80, CD86, MHC class II and intercellular adhesion molecule-1 (ICAM-1), and the ability to induce allogeneic T-lymphocyte proliferation in vitro, of a CD40- OSCC cell line, its CD40+ transfected derivative and null transfectants.

METHODS

OSCC cell lines and purified T lymphocytes were cocultured and T cell proliferation recorded. Phenotypes were analysed by flow cytometry.

RESULTS

After T lymphocyte proliferation, which all OSCC cell lines were able to induce, there was upregulation of MHC class II and ICAM-1. However, the CD40+ transfectants were the most immunologically potent and were the only cells to show increased expression of CD86 (as well as further upregulation of CD40 and a statistically insignificant rise in CD80). The effects of blocking antibodies on T-cell proliferation were only statistically significant with the CD40+ transfectants.

CONCLUSIONS

While not essential, expression of CD40 by OSCC cells is necessary for optimal induction of allogeneic T lymphocytes, possibly because of concurrent upregulation of other membrane-bound costimulatory molecules.

The Parent-into-F1 Model of Graft-vs-Host Disease as a Model of In Vivo T Cell Function and Immunomodulation

Since its description roughly 30 years ago, the parent-into-F1 model of graft-vs.-host disease has provided insights into the mechanisms of in vivo T cell activation and the pathogenesis of autoimmune conditions. A new and emerging role for the P-->F1 model is one of identifying agents with immunomodulatory activity and defining in vivo mechanisms that promote cell mediated or antibody mediated immune responses. Because F1 mice are not irradiated prior to donor cell transfer, the P-->F1 model has in the past not been strictly analogous to human hematopoetic stem cell transplantation. However with the advent of newer non-myeloablative conditioning regimens, the model may assume more relevance. In this article, we first provide a review of relevant earlier fundamental observations followed by a summary of recent work from our laboratory in which acute and chronic GVHD in this model have been used not only to study normal T cell responses in vivo but also to define mechanisms important in the pathogenesis of autoimmunity and immunomodulation.

Distinct effects of CD86-mediated costimulation on resting versus activated human CD4+ T cells

CD80 and CD86 are important in the initiation of T cell immunity. Although their costimulatory function has long been appreciated, it remains unclear whether the biological significance of the two B7 isoforms resides in their different patterns and kinetics of expression or whether differences exist in their function. We have addressed this issue using HLA-DR1 transfectants co-expressing CD80, CD86, or both molecules as stimulators for naïve, memory, and activated human CD4+ T cells. Both CD80 and CD86 efficiently costimulated alloresponses by unseparated peripheral blood CD4+ T cells; however, CD86 was substantially inferior in costimulating alloresponses by separated memory T cells, and completely incompetent in costimulating three human T cell clones. Furthermore, CD80/CD86 double transfectants stimulated lower responses by the clones than cells expressing CD80 alone. That CD86 was actively inhibitory rather than merely neutral was evidenced by the increase in response to the double CD80/CD86 APC when anti-CD86 antibody was added. Furthermore, addition of anti-CTLA-4 Fab to cultures of HLA-DR1 transfectants co-expressing CD86, fully restored the proliferative response. These results indicate that CD80 and CD86 mediate distinct signals in previously activated T cells, and demonstrate that CTLA-4 ligation may dominate the outcome of CD86-mediated costimulation of activated CD4+ T cells.

The synthetic peptide Trp-Lys-Tyr-Met-Val-D-Met as a novel adjuvant for DNA vaccine

Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm) is a synthetic peptide known to activate human neutrophils, monocytes and dendritic cells, resulting in the enhancement of superoxide generation, bactericidal activity, chemotactic migration and survival. In this study, we demonstrated that WKYMVm enhanced the surface expression of CD80, but not that of CD40, CD86 and MHC class II, on mouse bone marrow-derived dendritic cells which is one of the essential costimulatory signals for the induction of immune responses. Furthermore, when WKYMVm was codelivered with HIV, HBV and Influenza DNA vaccines, WKYMVm selectively enhanced the vaccine-induced CD8(+) T cell responses in a dose-dependent manner, in terms of IFN-gamma secretion and cytolytic activity. Our results indicate that a synthetic peptide, WKYMVm can function as a novel adjuvant for DNA vaccine.

Retinoic acid and polyriboinosinic:polyribocytidylic acid stimulate robust anti-tetanus antibody production while differentially regulating type 1/type 2 cytokines and lymphocyte populations

Retinoic acid (RA), a bioactive retinoid, and polyriboinosinic:polyribocytidylic acid (PIC) are known to promote immunity in vitamin A-deficient animals. In this study, we hypothesized that RA, PIC, and the combination can provide significant immunoadjuvant activity even in the vitamin A-adequate state. Six-week-old C57BL/6 mice were immunized with tetanus toxoid (TT) and treated with RA and/or PIC at priming in three independent studies of short and long duration. RA and PIC differentially regulated both primary and secondary anti-TT IgG isotypes, whereas the combination of RA + PIC stimulated the highest level of anti-TT IgG production and, concomitantly, a ratio of IgG1 to IgG2a similar to that of the control group. The regulation of Ab response was strongly associated with type 1/type 2 cytokine gene expression. Whereas RA reduced type 1 cytokines (IFN-gamma and IL-12), PIC enhanced both type 1 and type 2 cytokines (IL-4 and IL-12) and cytokine-related transcription factors. Despite the presence of PIC, the IL-4:IFN-gamma ratio was significantly elevated by RA. In addition, RA and/or PIC modulated NK/NKT cell populations and the level of expression of the costimulatory molecules CD80/CD86, evident 3 days after priming. Notably, the NKT:NK and CD80:CD86 ratios were correlated with the IL-4:IFN-gamma ratio, indicative of multiple converging modes of regulation. Overall, RA, PIC, and RA + PIC rapidly and differentially shaped the anti-tetanus Ig response. The robust, durable, and proportionate increase in all anti-TT IgG isotypes induced by RA + PIC suggests that this combination is promising as a means to enhance the Ab response to TT and similar vaccines.

Dendritic cells derived from metastatic cancer patients vaccinated with allogeneic dendritic cell-autologous tumor cell hybrids express more CD86 and induce higher levels of interferon-gamma in mixed lymphocyte reactions

Dendritic cells (DCs) are highly effective antigen-presenting cells that, when derived from cancer patients, seem to be functionally deficient. Herein, we show that vaccination with allogeneic DC-autologous tumor cell hybrids affects the phenotype and improves the function of monocyte-derived DCs (Mo-DCs) from cancer patients. Mononuclear cells were isolated from patients' peripheral blood by density gradient centrifugation, and adherent cells were cultured in medium containing GM-CSF plus IL-4 and, after 5 days, TNF-alpha. After 2 more days, Mo-DCs were harvested and their CD80, CD86, and CD83 expression was assessed by flow cytometry. They were also used as stimulators in mixed lymphocyte reactions (MLR), where IFN-gamma production was measured by ELISA. Mo-DCs from unvaccinated patients expressed significantly lower levels of CD86, and tended to express lower levels of CD83 than Mo-DCs from healthy donors. However, Mo-DCs generated after hybrid cell vaccination presented increased expression of the same markers and induced significantly higher levels of IFN-gamma in MLR. These results indicate that the use of allogeneic DC-based cancer vaccines induces recovery of DC function in metastatic cancer patients and, therefore, could precede the use of autologous DCs for vaccine preparation. Such an approach could be relevant and should be investigated in clinical trials.