The complexities of T-cell co-stimulation: CD28 and beyond

Are the Costimulatory Molecule Gene Polymorphisms (CTLA-4) Associated With Infection in Organ Transplantation? A Meta-Analysis

Organ transplantation has been linked to certain gene polymorphisms. The effect of gene polymorphisms-associated organ transplantation gene on infection, on the other hand, is yet unknown. The research studying the link between the CTLA-4 rs5742909, rs733618, rs4553808, rs231775, and polymorphisms of the organ transplantation gene and infection were found in PubMed, Web of Science, Scopus, and Embase, and the published articles from 2012 to 2020 were gathered. For the best estimation of the intended results, a random-effects model was used in this meta-analysis. In this study, 1,567 studies were initially included and 9 eligible studies were eligible for further analyses. A significant correlation between CTLA4+49 [A/G-231775 odds ratio (OR) = 077, 0.59-0.95] and CTLA4 [rs5742909TT OR: 0.09, 0.27-0.45] gene polymorphism with infection in organ transplantation was observed. Also, no significant association was found between other CTLA4 gene polymorphisms with infection in organ transplantation. Further studies involving gene-gene and gene-diet interactions should be conducted to investigate this association with infection.

Paradox-driven adventures in the development of cancer immunology and immunotherapy

After more than one hundred years of documented trials, immunotherapy has become a standard of care in the treatment of human cancer. Much of the knowledge that led to recent breakthroughs seems quite logical from today's point of view. However, what we now cite as facts were originally considered paradoxes, meaning something contrary to expectations or perceived opinion at the time. In order to make gains in the field of immunotherapy, one had to be willing to confront ideas and concepts that seemed to contradict one another, and reconcile how each could be true. This is what led to new knowledge and advances. Here, we highlight some of these paradoxes and the milestone discoveries that followed, each one critical for our understanding of immune checkpoint pathways. By outlining some of the steps that we took and the challenges that we overcame, we hope to inspire and encourage future generations of researchers to confront the paradoxes that still permeate the field.

A radiosensitivity gene signature and PD-L1 predict the clinical outcomes of patients with lower grade glioma in TCGA

PURPOSE

Identifying predictive factors for the clinical outcome of patients with lower grade gliomas following radiotherapy could help optimize patient treatments. Here, we investigate the predictive efficacy of both a previously identified "31-gene signature" and programmed death ligand-1 (PD-L1) expression.

MATERIAL AND METHODS

We identified 511 patients with lower grade glioma (Grade 2 and 3) in The Cancer Genome Atlas dataset and divided them into two clusters: radiosensitive (RS) and radioresistant (RR). Patients were also classified as PD-L1-high or PD-L1-low based on CD274 mRNA expression. Five-year survival rates were compared across patient groups, and differentially expressed genes were identified via a gene enrichment analysis.

RESULTS

Among 511 patients with lower grade glioma in The Cancer Genome Atlas dataset, we identified a group that was characterized by radioresistant and high PD-L1 (the PD-L1-high-RR group). Multivariate Cox models demonstrated that the membership in the PD-L1-high-RR can predict overall survival regarding to RT. Differentially expressed genes associated with the PD-L1-high-RR group were found to play a role in the immune response, including the T-cell receptor signaling pathway.

CONCLUSION

We tested the predictive value of a "31-gene signature" and PD-L1 expression status in a dataset of patients with lower grade glioma. Our results suggest that the patient population classified as the PD-L1-high-RR may benefit most from radiotherapy combined with anti-PD-1/PD-L1 treatment. Prospective clinical trial is necessary to validate the findings in a homogenous treated patient cohort.

Deletion of CD28 Co-stimulatory Signals Exacerbates Left Ventricular Remodeling and Increases Cardiac Rupture After Myocardial Infarction

BACKGROUND

Inflammatory responses, especially by CD4(+)T cells activated by dendritic cells, are known to be important in the pathophysiology of cardiac repair after myocardial infarction (MI). Although co-stimulatory signals through B7 (CD80/86) and CD28 are necessary for CD4(+)T cell activation and survival, the roles of these signals in cardiac repair after MI are still unclear.

METHODS AND RESULTS

C57BL/6 (Control) mice and CD28 knockout (CD28KO) mice were subjected to left coronary artery permanent ligation. The ratio of death by cardiac rupture within 5 days after MI was significantly higher in CD28KO mice compared with Control mice. Although there were no significant differences in the infarct size between the 2 groups, left ventricular end-diastolic and end-systolic diameters were significantly increased, and fractional shortening was significantly decreased in CD28KO mice compared with Control mice. Electron microscopic observation revealed that the extent of extracellular collagen fiber was significantly decreased in CD28KO mice compared with Control mice. The number of α-smooth muscle actin-positive myofibroblasts was significantly decreased, and matrix metalloproteinase-9 activity and the mRNA expression of interleukin-1β were significantly increased in CD28KO mice compared with Control mice.

CONCLUSIONS

Deletion of CD28 co-stimulatory signals exacerbates left ventricular remodeling and increases cardiac rupture after MI through prolongation of the inflammatory period and reduction of collagen fiber in the infarct scars. (Circ J 2016; 80: 1971-1979).

Glycolysis inhibition as a cancer treatment and its role in an anti-tumour immune response

Increased glycolysis is the main source of energy supply in cancer cells that use this metabolic pathway for ATP generation. Altered energy metabolism is a biochemical fingerprint of cancer cells that represents one of the "hallmarks of cancer". The immune system can prevent tumour growth by eliminating cancer cells but this editing process ultimately results in poorly immunogenic cells remaining allowing for unchallenged tumour growth. In this review we look at the glycolysis pathway as a target for cancer treatments. We also examine the interplay between the glycolysis modulation and the immune response as an anti-cancer therapy.

The role of CTLA-4 and PD-1 in anti-tumor immune response and their potential efficacy against osteosarcoma

Immunotherapy is proved to be a promising therapeutic strategy against human malignancies. Evasion of immune surveillance is considered to be a major factor of malignant progression. Inhibitory receptors, especially CTLA-4 and PD-1, are found to play critical roles in the mediation of anti-tumor immune efficacy. Thus, antibodies targeting these immune checkpoints have emerged as the attractive treatment approaches to those patients with cancer. Osteosarcoma is highly malignant and current treatment remains a challenge, especially for those patients with metastasis. Despite some achievements, the effect of immunotherapy against osteosarcoma is still unsatisfactory. The present review attempts to show the role and mechanism of CTLA-4 and PD-1 in immune response and summarize the recent findings related to the effect of inhibitory receptor antibodies on the immune response against tumors, especially osteosarcoma, and the correlation between PD-1 or/and CTLA-4 expression and outcome of osteosarcoma patients. We further discuss the utilization of the combination therapy against osteosarcoma.

Comparative antitumor effect of preventive versus therapeutic vaccines employing B16 melanoma cells genetically modified to express GM-CSF and B7.2 in a murine model

Cancer vaccines have always been a subject of gene therapy research. One of the most successful approaches has been working with genetically modified tumor cells. In this study, we describe our approach to achieving an immune response against a murine melanoma model, employing B16 tumor cells expressing GM-CSF and B7.2. Wild B16 cells were injected in C57BL6 mice to cause the tumor. Irradiated B16 cells transfected with GM-CSF, B7.2, or both, were processed as a preventive and therapeutic vaccination. Tumor volumes were measured and survival curves were obtained. Blood samples were taken from mice, and IgGs of each treatment group were also measured. The regulatory T cells (Treg) of selected groups were quantified using counts of images taken by confocal microscopy. Results: one hundred percent survival was achieved by preventive vaccination with the group of cells transfected with p2F_GM-CSF. Therapeutic vaccination achieved initial inhibition of tumor growth but did not secure overall survival of the animals. Classical Treg cells did not vary among the different groups in this therapeutic vaccination model.

Analysis of cytotoxic T lymphocyte antigen-4 (CTLA-4) promoter -318C/T and +49A/G gene polymorphisms in Turkish patients with familial Mediterranean fever

Either the role of the adaptive immune system or the interaction between innate and adaptive immune systems in familial Mediterranean fever (FMF) is not clear so far. So, we planned to search for the interaction between the innate and adaptive immune systems in the pathogenesis of FMF by investigating polymorphism for CTLA-4 gene, which plays a role in controlling antigen presentation to T cells. We also aimed to investigate whether there is an association between -318C/T and +49A/G polymorphisms in the CTLA-4 gene and the main clinical features of the disease. 75 FMF patients and 179 controls were studied. Polymorphism was detected by the PCR-RFLP technique. The CT genotype and T allele frequencies of the -318C/T polymorphism and the haplotype frequency for the -318T/+49A in the CTLA-4 gene were higher in the FMF (21.3, 21.3, and 10.7 %) when compared with the controls (10.6, 10.6, and 5.3 %; P = 0.029, 0.044, and 0.029). However, these differences did not reach a statistically significant level after the Bonferroni correction. A significant linkage disequilibrium was found between the -318C/T and +49A/G polymorphisms in the CTLA-4 gene (D' = 0.997, r(2) = 0.027, P = 0.0002). Genotype and carrier frequencies of the CTLA-4 gene +49A/G polymorphism were not significantly different between FMF patients and healthy controls. No association was found between the studied polymorphisms and the main clinical features of the disease. Our findings suggest that although not statistically significant, higher frequencies of CTLA-4 gene -318CT genotype, T allele, and -318T/+49A haplotype in FMF patients may be related to the non-autoimmune pathogenesis of FMF.

Canine leishmaniosis. Modulation of macrophage/lymphocyte interactions by L. infantum

Canine leishmaniosis, caused by Leishmania infantum, is a systemic disease with variable clinical signs and a progressive evolution. This disease is characterized by impaired T cell-mediated immune response, which has been associated with disease chronicity and high mortality. Protective immunity against leishmaniosis is thought to be mediated by T cell and cytokine production. The T cell activation requires a primary signal delivered by the major histocompatibility complex (MHC) molecules present on the surface of antigen presenting cells, and a non-specific signal generated by co-stimulatory molecules. To characterize canine immune responses in the presence of L. infantum parasites or their antigens, in vitro cell cultures of canine macrophages and lymphocytes were established, and the macrophages presenting MHC class II molecules were evaluated as well as the expression of IL-12 and CD80-86 co-stimulatory molecules and nitric oxide production. The results showed for the first time the up-regulation of MHC class II molecules on the surface in canine peripheral blood monocyte-derived macrophages during L. infantum infection in the presence of lymphocytes. In addition, a lack of co-stimulatory expression and a reduced release of nitric oxide were observed, suggesting a loss of T cell function and consequently an inactivation of the macrophage oxidative burst which, in turn, favors the survival of Leishmania. These results constitute a new contribution for the understanding of the interactions between L. infantum and the canine immune system.

Modulation of Immune System by Kaposi's Sarcoma-Associated Herpesvirus: Lessons from Viral Evasion Strategies

Kaposi's sarcoma-associated herpesvirus (KSHV), a member of the herpesvirus family, has evolved to establish a long-term, latent infection of cells such that while they carry the viral genome gene expression is highly restricted. Latency is a state of cryptic viral infection associated with genomic persistence in their host and this hallmark of KSHV infection leads to several clinical-epidemiological diseases such as KS, a plasmablastic variant of multicentric Castleman's disease, and primary effusion lymphoma upon immune suppression of infected hosts. In order to sustain efficient life-long persistency as well as their life cycle, KSHV dedicates a large portion of its genome to encode immunomodulatory proteins that antagonize its host's immune system. In this review, we will describe our current knowledge of the immune evasion strategies employed by KSHV at distinct stages of its viral life cycle to control the host's immune system.

The upregulation of tumour necrosis factor-α and surface antigens expression on macrophages by bisphenol A-glycidyl-methacrylate

AIM

To evaluate the expression of tumour necrosis factor-α and surface antigens by bisphenol A-glycidyl-methacrylate (BisGMA) on murine macrophage cell line RAW264.7.

METHODOLOGY

Cytotoxicity was measured by tetrazolium bromide reduction assay. Tumour necrosis factor (TNF)-α was analysed by enzyme-linked immunosorbent assay. Cell surface antigens were investigated by flowcytometry. Statistical analyses were performed using anova followed by the Bonferroni's t-test for multigroup comparisons.

RESULTS

BisGMA exhibited cytotoxicity to RAW264.7 in a dose-dependent manner (P < 0.05) during 2-h incubation period. BisGMA was found to increase TNF-α secretion in a dose-dependent manner (P < 0.05). In addition, CD11, CD14, CD45, CD54, CD40, CD80, and MHC II were significantly stimulated by BisGMA in a dose-dependent manner (P < 0.05). However, MHC I expression was not affected by BisGMA (P > 0.05).

CONCLUSIONS

Taken together, the ability of macrophages to induce an appropriate immune response when exposed to BisGMA has the potential to upregulate TNF-α production and expression of surface antigens.

Dendritic cells from X-linked hyper-IgM patients present impaired responses to Candida albicans and Paracoccidioides brasiliensis

BACKGROUND

Patients with X-linked hyper-IgM syndrome (X-HIGM) due to CD40 ligand (CD40L) mutations are susceptible to fungal pathogens; however, the underlying susceptibility mechanisms remain poorly understood.

OBJECTIVE

To determine whether monocyte-derived dendritic cells (DCs) from patients with X-HIGM exhibit normal responses to fungal pathogens.

METHODS

DCs from patients and controls were evaluated for the expression of costimulatory (CD80 and CD86) and MHC class II molecules and for their ability to produce IL-12 and IL-10 in response to Candida albicans and Paracoccidioides brasiliensis. We also evaluated the ability of C albicans- and P brasiliensis-pulsed mature DCs to induce autologous T-cell proliferation, generation of T helper (T(H)) 17 cells, and production of IFN-γ, TGF-β, IL-4, IL-5, and IL-17.

RESULTS

Immature DCs from patients with X-HIGM showed reduced expression of CD80, CD86, and HLA-DR, which could be reversed by exogenous trimeric soluble CD40L. Most important, mature DCs from patients with X-HIGM differentiated by coculturing DCs with fungi secreted minimal amounts of IL-12 but substantial amounts of IL-10 compared with mature DCs from normal individuals. Coculture of mature DCs from X-HIGM patients with autologous T cells led to low IFN-γ production, whereas IL-4 and IL-5 production was increased. T-cell proliferation and IL-17 secretion were normal. Finally, in vitro incubation with soluble CD40L reversed the decreased IL-12 production and the skewed T(H)2 pattern response.

CONCLUSION

Absence of CD40L during monocyte/DC differentiation leads to functional DC abnormalities, which may contribute to the susceptibility to fungal infections in patients with X-HIGM.

Immune evasion by Kaposi's sarcoma-associated herpesvirus

Persistent viral infections are often associated with serious diseases, primarily by altering functions of the host immune system. The hallmark of Kaposi's sarcoma-associated herpesvirus (KSHV) infection is the establishment of a life-long persistent infection, which leads to several clinical, epidemiological and infectious diseases, such as Kaposi's sarcoma, a plasmablastic variant of multicentric Castleman's disease, and primary effusion lymphoma. To sustain an efficient life-long persistency, KSHV dedicates a large portion of its genome to encoding immunomodulatory proteins that antagonize the immune system of its host. In this article, we highlight the strategies KSHV uses to evade, escape and survive its battle against the host's immune system.

Blockade of programmed death-1 in young (New Zealand black x New Zealand white)F1 mice promotes the activity of suppressive CD8+ T cells that protect from lupus-like disease

The programmed death-1 (PD-1)/programmed death-1 ligand 1 (PD-L1) pathway regulates both stimulatory and inhibitory signals. In some conditions, PD-1/PD-L1 inhibits T and B cell activation, induces anergy, and reduces cytotoxicity in CD8(+) T cells. In other conditions, PD-l/PD-L1 has costimulatory effects on T cells. We recently showed that induction of suppressive CD8(+)Foxp3(+) T cells by immune tolerance of lupus-prone (New Zealand black × New Zealand white)F(1) (BWF(1)) mice with the anti-DNA Ig-based peptide pConsensus (pCons) is associated with significantly reduced PD-1 expression on those cells. In this study, we tested directly the role of PD-1 by administering in vivo neutralizing Ab to PD-1 to premorbid BWF(1) and healthy control mice. Anti-PD-1-treated mice were protected from the onset of lupus nephritis for 10 wk, with significantly improved survival. Although the numbers of T cells declined in aging control mice, they were maintained in anti-PD-1-treated mice, including CD8(+)Foxp3(+) T cells that suppressed syngeneic CD4(+)CD25(-) T cell proliferation and IFN-γ production, reduced production of IgG and anti-dsDNA IgG, induced apoptosis in syngeneic B cells, and increased IL-2 and TGF-β production. The administration of anti-PD-1 Ab to BWF(1) mice after induction of tolerance with pCons abrogated tolerance; mice developed autoantibodies and nephritis at the same time as control mice, being unable to induce CD8(+)Foxp3(+) T suppressor cells. These data suggest that tightly regulated PD-1 expression is essential for the maintenance of immune tolerance mediated by those CD8(+)Foxp3(+) T cells that suppress both T(h) cells and pathogenic B cells. PD-1 regulation could represent a target to preserve tolerance and prevent autoimmunity.

Cell density plays a critical role in ex vivo expansion of T cells for adoptive immunotherapy

The successful ex vivo expansion of a large numbers of T cells is a prerequisite for adoptive immunotherapy. In this study, we found that cell density had important effects on the process of expansion of T cells in vitro. Resting T cells were activated to expand at high cell density but failed to be activated at low cell density. Activated T cells (ATCs) expanded rapidly at high cell density but underwent apoptosis at low cell density. Our studies indicated that low-cell-density related ATC death is mediated by oxidative stress. Antioxidants N-acetylcysteine, catalase, and albumin suppressed elevated reactive oxygen species (ROS) levels in low-density cultures and protected ATCs from apoptosis. The viability of ATCs at low density was preserved by conditioned medium from high-density cultures of ATCs in which the autocrine survival factor was identified as catalase. We also found that costimulatory signal CD28 increases T cell activation at lower cell density, paralleled by an increase in catalase secretion. Our findings highlight the importance of cell density in T cell activation, proliferation, survival and apoptosis and support the importance of maintaining T cells at high density for their successful expansion in vitro.

Investigation of CTLA-4 and CD28 gene polymorphisms in a group of Turkish patients with colorectal cancer

Colorectal cancer (CRC), also called colon cancer or bowel cancer, includes cancerous growths in the colon, rectum and appendix. The immune system is an important defence mechanism against cancer and is often dysfunctional in patients with malignancies. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and CD28 genes encode receptors that provide negative and positive signals, respectively. Polymorphisms in these genes can affect their functions. In this study, we aimed to investigate the association of cancer with the frequencies and roles of CTLA-4/+49A > G (exon 1) and -318C > T (promoter), and CD28/IVS3 + 17T > C (intron 3 position + 17). These polymorphisms were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 218 Turkish subjects (56 patients with CRC and 162 healthy controls). No statistically significant differences in the genotype distributions of CTLA-4/+49GG (1.8% vs. 6.8%, odds ratio (OR) = 0.250, P = 0.305) and CTLA-4/-318TT (0% vs. 0.6%, OR = 1.006, P = 1.000), and CD28/IVS3 + 17CC (8.9% vs. 3.7%, OR = 0.2411, P = 0.155) between patients with CRC and healthy controls, were observed. We also found that there were no significant differences in the frequencies of CTLA-4/+49G (18.8% vs. 20.1%, OR = 0.920, P = 0.891) and CTLA-4/-318T (7.1% vs. 4.3%, OR = 1.653, P = 0.314), and CD28/IVS3 + 17C alleles (25.9% vs. 19.1%, OR = 1.353, P = 0.139) between two study groups. Present results suggested that CTLA-4 and CD28 gene polymorphisms did not play an important role in Turkish patients with CRC.

Microarray analysis reveals similarity between CD8+CD28- T cells from young and elderly persons, but not of CD8+CD28+ T cells

We isolated highly purified CD8+CD28+ and CD8+CD28- T cell populations from healthy young and elderly persons for gene expression profiling using Affymetrix oligonucleotide microarrays. We demonstrate that the gene expression profile of CD8+CD28- T cells is very similar in young and elderly persons. In contrast, CD8+CD28+ in elderly differ from CD8+CD28+ in young persons. Hierarchical clustering revealed that CD8+CD28+ in elderly are located between CD8+CD28+ in young and CD8+CD28- (young and old) T cells regarding their differentiation state. Our study demonstrates a dichotomy of gene expression levels between CD8+CD28+ T cells in young and elderly persons but a similarity between CD8+CD28- T cells in young and elderly persons. As CD8+CD28+ T cells from elderly and young persons are distinct due to a different composition of the population, these results suggest that the gene expression profile does not depend on chronological age but depends on the differentiation state of the individual cell types.

Aging-related differences in basal heat shock protein 70 levels in lymphocytes are linked to altered frequencies of lymphocyte subsets

Cell stress responses are ubiquitous in all organisms and are characterized by the induced synthesis of heat shock proteins (Hsp). Previous studies as well as recent reports by our group have consistently suggested that aging leads to an increase in the basal levels of Hsp70. Here we extend these studies by examining the differential Hsp70 response of peripheral blood lymphocyte (PBL) subsets. It is well established that with aging, one of the major changes in the T cell pool is an expansion of T cells with the memory phenotype as well as those deficient for the CD28 molecule. To determine if alterations in the frequency of T cell subsets might be responsible for the observations, we have carried out a more comprehensive flow cytometric analysis of the various phenotypes of PBL under unstimulated conditions. Cells were obtained from 10 young and 10 elderly normal subjects. The basal Hsp70 levels in the various PBL phenotypes were comparable between young and elderly subjects. However, different patterns of Hsp70 response were noticed among the PBL subtypes, which were similar in both young and elderly subjects. In particular, the memory cell phenotypes produced more Hsp70 than the naïve phenotypes. These results suggest that aging-related changes in basal Hsp70 levels in PBL are linked to the altered frequency of lymphocyte subsets and not to increases in aged lymphocytes per se. In addition, the increase in Hsp70 can be interpreted as the result of a tendency towards more pronounced cellular differentiation in aging.

Immune activation driven by CTLA-4 blockade augments viral replication at mucosal sites in simian immunodeficiency virus infection

The importance of chronic immune activation in progression to AIDS has been inferred by correlative studies in HIV-infected individuals and in nonhuman primate models of SIV infection. Using the SIV(mac251) macaque model, we directly address the impact of immune activation by inhibiting CTLA-4, an immunoregulatory molecule expressed on activated T cells and a subset of regulatory T cells. We found that CTLA-4 blockade significantly increased T cell activation and viral replication in primary SIV(mac251) infection, particularly at mucosal sites, and increased IDO expression and activity. Accordingly, protracted treatment with anti-CTLA-4 Ab of macaques chronically infected with SIV(mac251) decreased responsiveness to antiretroviral therapy and abrogated the ability of therapeutic T cell vaccines to decrease viral set point. These data provide the first direct evidence that immune activation drives viral replication, and suggest caution in the use of therapeutic approaches for HIV infection in vivo that increase CD4(+) T cell proliferation.

IL-7/STAT5 cytokine signaling pathway is essential but insufficient for maintenance of naive CD4 T cell survival in peripheral lymphoid organs

Constitutive expression of suppressors of cytokine signaling (SOCS)1 in T lineage in vivo attenuated cytokine signaling and resulted in a dramatic reduction in the number of naive CD44(low)CD62L(high) CD4 T cells in the spleen. After adoptive transfer of thymocytes from SOCS1 transgenic mice into normal recipients, naive CD4 T cells rapidly disappeared from the spleen within 1 wk. Likewise, T cell-specific deletion of STAT5a/b in vivo resulted in a similar phenotype characterized by loss of naive CD4 T cells. Thus, STAT5-mediated signaling is crucial for promoting naive T cell survival. However, forced expression of constitutively active STAT5 failed to rescue CD4 T cells in SOCS1 transgenic mice, implying that STAT5 activation is necessary but not sufficient for naive CD4 T cell survival. Although blockade of the IL-7R, a SOCS1 target, resulted in clear inhibition of naive T cell survival, the effect occurred 3 wk after anti-IL-7R Ab treatment, but not at earlier time points. These results suggest that IL-7-mediated STAT5 activation is essential for long-term survival of naive CD4 cells after export from thymus, and that another SOCS1-sensitive cytokine is critical for short-term naive T cell survival.

Analysis of CD28 and CTLA-4 gene polymorphisms in Turkish patients with Behcet's disease

In this study we aimed to investigate IVS3 +17T/C single nucleotide polymorphism (SNP) of CD28 gene, +49A/G and -318C/T SNPs of CTLA-4 gene in patients with Behçet's disease (BD) and their potential association to the main clinical features of the disease. These polymorphisms were investigated in a Turkish population of 123 patients with BD and 179 healthy controls, by using PCR-RFLP technique. HLA-B*51 genotype was also studied in both groups by using PCR-SSP. The frequency of IVS3 +17TC genotype of the CD28 gene was significantly increased in BD patients compared to controls (43.6% vs. 31.2%, OR = 1.663, 95% CI = 1.033-2.679, P = 0.039). CTLA-4 +49GG genotype frequency was found to be significantly lower in patients with BD than those of healthy controls (4% vs. 10.6%, OR = 0.357, 95% CI = 0.130-0.983, P = 0.05). Genotype and allele frequencies of the CTLA-4-318C/T polymorphism between the BD and healthy control groups were not significantly different (12.2% vs. 10.6%, OR = 1.170, 95% CI = 0.570-2.402, P = 0.713). There were no associations between the studied polymorphisms and the main clinical features of BD. The frequencies of HLA-B*51 were 60.3% and 30.7% in BD and control groups, respectively (OR = 3.429, 95% CI = 2.115-5.559, P = 0.0001). Association between HLA-B*51 and each studied polymorphism did not reach to significant levels (OR = 0.479, 95% CI = 0.228-1.004, P = 0.064 for CD28 IVS3 +17TT genotype; OR = 2.180, 95% CI = 1.025-4.639, P = 0.061 for TC genotype; OR = 1.570, 95% CI = 0.870-2.836, P = 0.146 for C allele). These results may suggest that CD28 IVS3 +17TC genotype may be a risk factor for the development of BD, on the contrary CTLA-4 +49GG genotype may be protective in the studied Turkish population.

Human mesenchymal stem cells induce T cell anergy and downregulate T cell allo-responses via the TH2 pathway: relevance to tissue engineering human heart valves

To generate an ''off the shelf'' tissue-engineered heart valve, the cells would need to be of allogeneic origin. Here, we report the possibility of using human bone marrow-derived mesenchymal stem cells (MSCs) as a suitable allogeneic cell source for tissue-engineered heart valves. Proliferative responses of primary and primed CD4+ T cells to allogeneic MSCs were examined. A protein microarray system was used to detect soluble factors from supernatants collected from the T cell assays. MSCs are poor stimulators of primary and primed CD4+ T cell proliferation, despite provision of B7-1 trans-co-stimulation. MSCs not only directly inhibited primary and primed T cell responses to allogeneic peripheral blood mononuclear cells (PBMCs), but 24-h pre-culture of T cells with MSCs suppressed subsequent T cell proliferative responses to allogeneic PBMCs in a contact-dependent manner. Analysis of supernatants revealed a distinctly different cytokine profile after co-culture of T cells with MSCs than with PBMCs or endothelial cells. Pro-inflammatory Th1 cytokines interleukin (IL)-1alpha and beta, interferon (IFN)gamma, and tumor necrosis factor (TNF)alpha were downregulated, whereas, anti-inflammatory Th2 cytokines IL-3, IL-5, IL-10, and IL-13 and the Th2 chemokine I-309, a chemoattractant for regulatory T cells, were upregulated. Further analysis revealed that after co-culture with MSCs, the T cells exhibited a regulatory phenotype (CD4+ CD25(lo) CD69(lo) FoxP3+). MSCs downregulate T cell responses through direct contact and secretion of anti-inflammatory and tolerogenic cytokines, which may involve the recruitment of regulatory T cells. This implies that allogeneic MSCs could be a suitable cell source for tissue engineering a heart valve.

CD28-dependent differentiation into the effector/memory phenotype is essential for induction of arthritis in interleukin-1 receptor antagonist-deficient mice

OBJECTIVE

Interleukin-1 receptor antagonist (IL-1Ra)-deficient mice on a BALB/c background spontaneously develop a chronic inflammatory polyarthropathy closely resembling that of rheumatoid arthritis in humans. To elucidate the role of CD28 costimulatory signals in the development of this disease, we studied IL-1Ra/CD28-double-deficient mice.

METHODS

We crossed IL-1Ra-deficient mice with CD28-deficient mice and observed the incidence and severity of arthritis. To investigate functions of IL-1Ra/CD28-double-deficient T cells, cells were stimulated with CD3 monoclonal antibody or allogeneic antigen-presenting cells (APCs) and their proliferative responses and levels of cytokine production were measured.

RESULTS

Disease severity was lower in IL-1Ra/CD28-double-deficient mice than in mice that were deficient only in IL-1Ra, although incidence of arthritis was not affected by the presence or absence of CD28. When pathogenic IL-1Ra-KO T cells were transferred into nude mice, severe arthritis developed. Even though T cells from double-deficient mice showed the same diminished proliferative capacity as was seen in T cells from CD28-single-deficient animals, nude mice into which double-deficient T cells were transferred never developed arthritis.

CONCLUSION

These findings indicate that IL-1Ra/CD28-double-deficient T cells can be activated by IL-1Ra-deficient activated APCs, resulting in induction of arthritis; however, these T cells did not induce the disease under normal conditions, because they did not differentiate into effector/memory phenotype.

Inhibition of polymorphonuclear leukocyte-mediated graft damage synergizes with short-term costimulatory blockade to prevent cardiac allograft rejection

BACKGROUND

The early inflammatory response during reperfusion of cardiac allografts is initiated by the infiltration of polymorphonuclear leukocytes (PMNs) into the graft. The impact of early PMN infiltration on allograft rejection compared with long-term graft survival remains poorly understood.

METHODS AND RESULTS

We tested the role of CXCR2, the receptor for 2 PMN attractant chemokines, KC/CXCL1 and MIP-2/CXCL2, on intragraft inflammation and vascularized cardiac allograft rejection in a murine model. Compared with allografts retrieved from control recipients, both PMN infiltration and intragraft proinflammatory cytokine expression were significantly attenuated in allografts from CXCR2-antisera-treated wild-type or from CXCR2(-/-) recipients. Adoptive transfer of alloantigen-primed T cells rapidly infiltrated and rejected allografts in control recipients, but T-cell infiltration was significantly decreased in recipients depleted of PMNs at transplantation. The influence of early PMN-mediated inflammation on the therapeutic efficacy of costimulatory blockade to prevent allograft rejection was tested. Short-term treatment of recipients with anti-CD154 mAb or CTLA-4 Ig induced modest prolongation of cardiac allograft survival. However, CD154 mAb or CTLA-4 Ig treatment, combined with either peritransplantation PMN depletion or antibodies specific for KC/CXCL1 plus MIP-2/CXCL2, prolonged cardiac allograft survival beyond 100 days.

CONCLUSIONS

Results suggest that strategies attenuating PMN-mediated tissue damage during reperfusion significantly improve the efficacy of short-term costimulatory blockade to prevent T-cell-mediated rejection of cardiac allografts.

Effects of allergen inhalation and oral glucocorticoid on concentrations of serum-soluble CD86 in allergic asthmatics

The aim of the present study was to investigate effects of allergen inhalation and oral glucocorticoid on concentration of serum soluble CD86 in patients with allergic asthma. Our results showed that the serum soluble CD86 concentrations in the dual responder group increased from 491.8 +/- 15.4 IU/ml before allergen inhalation to 603.8 +/- 19.3 IU/ml 24 h after allergen inhalation. In the isolated early responders, there was no significant increase in serum soluble CD86 concentrations after allergen inhalation compared with baseline levels. There was a significant decrease in serum soluble CD86 concentrations after 2 weeks of glucocorticoid therapy (448.3 +/- 15.1 IU/ml) compared with baseline values (532.7 +/- 12.3 IU/ml), whereas there was no significant difference in the placebo group. This study has demonstrated that serum soluble CD86 concentrations increased after allergen inhalation in sensitized asthmatic subjects, and that serum sCD86 concentrations were downregulated by prednisolone therapy.

Effects of allergen inhalation and oral glucocorticoid on serum soluble CTLA-4 in allergic asthmatics

BACKGROUND

The serum soluble cytotoxic T lymphocyte associated antigen-4 (sCTLA-4) concentration is significantly elevated in patients with asthma, and sCTLA-4 concentration correlate with the severity of asthma. The aim of the present study was to investigate effects of allergen inhalation and oral glucocorticoid on concentration of serum sCTLA-4 in patients with allergic asthma.

METHODS

Allergen inhalation challenge was conducted in allergic asthmatics with isolated early asthma response and those with dual asthma response. In a randomized, double-blind, placebo-controlled, parallel group fashion, prednisolone or placebo was give orally once a day for 2 weeks. Venous blood samples were collected before and after allergen inhalation or prednisolone administration for obtaining sera. The serum sCTLA-4 concentrations were determined using enzyme-linked immunosorbent assay.

RESULTS

The serum sCTLA-4 concentrations in the dual responder group increased from 29.0 (14.5-43.7) microg/l [median (25-75 percentiles)] before allergen inhalation to 44.0 (24.3-61.3) microg/l 24 h after allergen inhalation. In the isolated early responders, there were no significant increase in serum sCTLA-4 concentrations after allergen inhalation compared with baseline levels. There was a significant decrease in serum sCTLA-4 concentrations after 2 weeks of glucocorticoid therapy [22.0 (15.5-31.0) microg/l] compared with baseline values [37.0 (19.5-53.0) microg/l], whereas there was no significant difference in the placebo group.

CONCLUSION

This study has demonstrated that serum sCTLA-4 concentrations increased after allergen inhalation in sensitized asthmatic subjects, and that serum sCTLA-4 concentrations were downregulated by prednisolone therapy.

Redirected primary T cells harboring a chimeric receptor require costimulation for their antigen-specific activation

Chimeric receptor (CR)–redirected lymphocytes (T bodies) have great potential in the eradication of tumor cells. To extend this approach to target cells that do not express surface ligands to costimulatory receptors (eg, cancer cells), we have generated an antibody-based tripartite chimeric receptor (TPCR) that contains scFv linked to the costimulatory molecule, CD28 without its ligand-binding domain, and to the cytoplasmic moiety of the FcRγ subunit. In this study, we tested the ability of 2,4,6-trinitrophenyl (TNP)–specific TPCR to drive primary, naïve T cells derived from CR-transgenic (Tg) mice to undergo full activation. As a control, we used Tg mice expressing a similar transgene but lacking the signaling region of CD28 (Tg-TPCRΔCD28). Only T cells from the TPCR-Tg and not the CD28-truncated TPCR-Tg mice could undergo activation following stimulation on hapten-modified target cells not expressing B7. Moreover, when stimulated with TNP protein displayed on plastic, the TPCR-Tg T cells expressing the entire TPCR gene became fully activated for proliferation, interleukin 2 production, protection from apoptosis, and killing of TNP-modified target cells. Finally, TPCR-Tg mice manifested a delayed-type hypersensitivity response following skin challenge in the absence of priming. Taken together, our results suggest that the TPCR is the receptor configuration of choice for clinical applications using primary T or stem cells.

Potential immunogenicity of adult T cell leukemia cells in vivo

Experimental vaccines targeting human T cell leukemia virus type-I (HTLV-I) Tax have been demonstrated in a rat model of HTLV-I-induced lymphomas. However, the scarcity of HTLV-I-expression and the presence of defective HTLV-I-proviruses in adult T cell leukemia (ATL) cells have raised controversy about the therapeutic potential of HTLV-I-targeted immunotherapy in humans. We investigated the expression of HTLV-I antigens in fresh ATL cells by using both in vitro and in vivo assays. In flow cytometric analysis, we found that 3 of 5 acute-type and six of fifteen chronic-type ATL patients tested showed significant induction of HTLV-I Tax and Gag in their ATL cells in a 1-day culture. Concomitantly with HTLV-I-expression, these ATL cells expressed co-stimulatory molecules such as CD80, CD86 and OX40, and showed elevated levels of antigenicity against allogeneic T cells and HTLV-I Tax-specific cytotoxic T-lymphocytes (CTL). Representative CTL epitopes restricted by HLA-A2 or A24 were conserved in 4 of 5 acute-type ATL patients tested. Furthermore, spleen T cells from rats, which had been subcutaneously inoculated with formalin-fixed uncultured ATL cells, exhibited a strong interferon gamma-producing helper T cell responses specific for HTLV-I Tax-expressing cells. Our study indicated that ATL cells from about half the patients tested readily express HTLV-I antigens including Tax in vitro, and that ATL cells express sufficient amounts of Tax or Tax-induced antigens to evoke specific T cell responses in vivo.

B7-H1 expression on non-small cell lung cancer cells and its relationship with tumor-infiltrating lymphocytes and their PD-1 expression

PURPOSE

B7-H1/PD-L1 (B7-H1) and B7-DC/PD-L2 (B7-DC) are ligands for the receptor PD-1, which is known to negatively regulate T-cell activation. In the present study, we investigated the expression of B7-H1 and B7-DC in tumor specimens of non-small cell lung cancer and their relationships with clinicopathological variables and postoperative survival. Furthermore, we examined the correlation between B7-H1 expression on tumor cells and the number of tumor-infiltrating lymphocytes (TILs) or PD-1 expression on TILs.

EXPERIMENTAL DESIGN

The expression of B7-H1 and B7-DC in 52 surgically resected specimens of non-small cell lung cancer was evaluated immunohistochemically.

RESULTS

Expression of B7-H1 and B7-DC was focally observed in all non-small cell lung cancer tumor specimens. No relationship was found between the expression of B7-H1 or B7-DC and clinicopathological variables or postoperative survival. However, in the same sections evaluated, significantly fewer TILs were identified in B7-H1-positive tumor regions than in B7-H1-negative tumor regions in a subset of five patients (P = 0.01). Moreover, the percentage of TILs expressing PD-1 was significantly lower in B7-H1-positive tumor regions than in B7-H1-negative tumor regions (P = 0.02).

CONCLUSIONS

The expression of B7-H1 on tumor cells in local areas reciprocally correlated with the number of TILs, and this may contribute to negative regulation in antitumor immune responses in non-small cell lung cancer.

A Novel Bispecific Tetravalent Antibody Fusion Protein to Target Costimulatory Activity for T-cell Activation to Tumor Cells Overexpressing ErbB2/HER2

Persistent activation of T-lymphocytes requires two signals: one is initiated by T-cell receptor binding to antigenic peptide presented by MHC molecules. In addition, binding of the B7 family members CD80 or CD86 on professional antigen presenting cells to CD28 on T cells is considered to provide an important costimulatory signal. Activation without costimulation induces T-cell unresponsiveness or anergy. To selectively localize costimulatory activity to the surface of tumor cells and enhance activation of tumor-specific T cells, we have developed a novel molecular design for bispecific costimulatory proteins with antibody-like structure. Within a single polypeptide chain we have assembled the IgV-like, CD28-binding domain of human CD86 (CD86(111)) together with hinge, CH2 and CH3 domains of human IgG1, and the scFv(FRP5) antibody fragment which recognizes the ErbB2 (HER2) protooncogene present at high levels on the surface of many human tumor cells. Upon expression in the yeast Pichia pastoris, the resulting CD86(111)-IgG-scFv(FRP5) protein could be purified as a homodimeric, tetravalent molecule from culture supernatants using single-step affinity chromatography. Bispecific binding of the molecule to ErbB2 on the surface of tumor cells and to the B7 counter receptor CTLA-4 was demonstrated by FACS analysis. Potent costimulatory activity of chimeric CD86(111)-IgG-scFv(FRP5) was confirmed by its ability to stimulate the proliferation of primary human lymphocytes pre-activated by low concentrations of anti-CD3 antibody. Our results suggest that such multivalent soluble proteins which combine specific targeting to tumor cells with costimulatory activity may become useful tools to elicit and/or improve T-cell mediated, tumor-specific immune responses.

The systemic immune response is more prominent than the mucosal immune response in the pathogenesis of periodontal disease

BACKGROUND/AIM

The diseased periodontium appears to express features of a systemic and a mucosal immune response. Our aims were to determine differences in immunoglobulin expression between gingivitis and periodontitis lesions and to ascertain whether immune and inflammatory cells were recruited into the diseased periodontium by the mucosal addressin adhesion molecule (MAdCAM-1).

METHODS

In situ hybridization and immunohistochemistry were used to detect the expression of chemokines, adhesion molecules and immunoglobulins in tissue sections of gingival and granulation tissues excised from periodontitis-affected sites and of healthy tissue and gingivitis-affected tissue excised during crown-lengthening procedures.

RESULTS

Greater numbers of plasma cells were observed in periodontitis gingival/granulation tissue lesions compared with gingivitis lesions. While IgA1 were predominant in all lesions, IgA2 and J-chain expressing plasma cells were present in increased proportions in gingival tissues compared with granulation tissue. Intracellular adhesion molecule-1 (ICAM-1) was higher in periodontitis than in gingivitis and interleukin-8 mRNA was higher in lesions with a pronounced neutrophil infiltrate. Vascular cell adhesion molecule-1 (VCAM-1) localized to the deep connective tissue and indicated the presence of a systemic type of immune response in this region. Periodontal tissues (n=71 biopsies) did not appear to express MAdCAM-1, in positive control sections of small intestine where it was detected.

CONCLUSION

Overall, the systemic-type immune response is predominant, and although the mucosal immune response is minor and limited to the superficial tissues it may have an important role in the host defense to periodontal pathogens.

Differential T-cell activation by B7-1 expression

T-cell receptor-mediated T-cell activation requires cosimulation signal, which can be provided by B7-1 molecule. Our previous study demonstrated that the coexpression of a covalent peptide/major histocompatibility complex class II molecule complex and costimulatory molecule B7-1 by recombinant adenovirus leads to synergy in peptide-specific T-cell activation. However, the viral antigen-specific T-cell activation is not enhanced by B7-1 expressed by the adenovirus. To verify the differential T cell activation by B7-1 and investigate its underlying mechanisms, we constructed an adenovirus coexpressing a covalent complex of hen egg lysozyme peptide/I-Ak (HEL46-61/I-Ak) and B7-1 in the present study. In vivo studies revealed that HEL46-61-specific T-cell response, but not viral antigen-specific T-cell response, was enhanced by B7-1 expression mediated by the adenovirus, suggesting that exogenous B7-1 expression may regulate T-cell response to these two different antigens through distinct mechanisms. Furthermore, our results revealed that antigen-presenting cells were not susceptible to adenovirus infection in vivo. Based on these findings, the possible mechanism of differential B7-1 costimulation on peptide-specific and viral antigen-specific T-cell activation is discussed.

Expression of the costimulatory molecule B7-H2 (inducible costimulator ligand) by human airway epithelial cells

Tissue structural cells are known in some situations to play a role in the presentation of antigen and in immunoregulation. We assessed the expression of B7 homologs, known to be involved in antigen presentation and lymphocyte costimulation, in human airway epithelial cells. Flow cytometry performed on the airway epithelial cell line BEAS-2B, as well as primary bronchial epithelial cells (PBEC), showed that B7-H2 was constitutively expressed on both BEAS-2B and PBEC, whereas B7-1 and B7-2 were undetectable on either epithelial cell type. B7-H2 expression was confirmed by Western blot using a specific antibody. Stimulation with various cytokines, including tumor necrosis factor-alpha, interferon-gamma, and interleukin-4, slightly downregulated B7-H2 expression detected by flow cytometry, but did not significantly alter the apparent level of protein as assessed by Western blotting. Northern blotting detected mRNA for B7-H2 and B7-1, but not B7-2. B7-H2 was cloned from BEAS-2B cells and the sequence verified. Expression of B7-H2 mRNA was detected by real-time reverse transcriptase-polymerase chain reaction in PBEC from three independent donors. Immunohistochemical analysis of airway derived from autopsies revealed expression of B7-H2 in human airway epithelial cells. These results demonstrate that airway epithelial cells express the costimulatory molecule B7-H2, and suggest the possibility that B7-H2 may participate in antigen presentation by epithelial cells.

A role of suppressor of cytokine signaling 3 (SOCS3/CIS3/SSI3) in CD28-mediated interleukin 2 production

Suppressor of cytokine signaling (SOCS)3 has been characterized as a negative feedback regulator in cytokine-mediated Janus kinase signal transducer and activator of transcription signaling. However, this study shows that T cells from transgenic mice expressing SOCS3 exhibit a significant reduction in interleukin (IL)-2 production induced by T cell receptor cross-linking when T cells are costimulated with CD28. Decreased protein expression in SOCS3(+/-) mice enhanced CD28-mediated IL-2 production, clearly indicating the correlation between expression level of SOCS3 and IL-2 production ability. The SOCS3 protein interacted with phosphorylated CD28 through its SH2 domain but not the kinase inhibitory region. In addition, a point mutation in the SOCS3 SH2 domain attenuated the inhibition of CD28 function in IL-2 promoter activation. Committed T helper (Th)2 cells exclusively expressed SOCS3 and production of Th2 cytokines, such as IL-4 and IL-5, was much less dependent on CD28 costimulation compared with interferon gamma and IL-2 production in Th1 cells. Consistent with this notion, the expression level of SOCS3 in early T cell activation influenced the ability of IL-2 production induced by CD28 costimulation. Therefore, the SOCS3 may play an alternative role in prohibiting excessive progression of CD28-mediated IL-2 production.

Naturally occurring human IgM antibody that binds B7-DC and potentiates T cell stimulation by dendritic cells

A human IgM Ab, serum-derived human IgM 12 (sHIgM12), is identified that binds mouse and human dendritic cells (DC), inducing dramatic immunopotentiation following treatment of the mouse DC in vitro. Competition, transfection, and knockout studies identified the ligand on mouse DC as the costimulatory molecule family member B7-DC. Potent T cell responses are stimulated by Ag-pulsed DC treated with the sHIgM12 Ab in vitro and upon adoptive transfer of Ab-treated Ag-pulsed DC into animals. The multivalent structure of pentameric IgM provides the potential for cross-linking cell surface targets, endowing the soluble Abs with biological potential not normally associated with immune function. The ability of the sHIgM12 Ab to potentiate the immune response is dependent on the multimeric structure of IgM, as bivalent monomers do not retain this property. Furthermore, pretreatment of DC with IgM monomers blocks subsequent potentiation by intact IgM pentamers, an indication that cross-linking of B7-DC on the cell surface is critical for potentiation of Ag presentation. These findings imply that, in addition to known costimulatory roles, B7-DC can function as a receptor for signals delivered by cells expressing B7-DC ligands.

Involvement of PD-L1 on tumor cells in the escape from host immune system and tumor immunotherapy by PD-L1 blockade

PD-1 is a receptor of the Ig superfamily that negatively regulates T cell antigen receptor signaling by interacting with the specific ligands (PD-L) and is suggested to play a role in the maintenance of self-tolerance. In the present study, we examined possible roles of the PD-1/PD-L system in tumor immunity. Transgenic expression of PD-L1, one of the PD-L, in P815 tumor cells rendered them less susceptible to the specific T cell antigen receptor-mediated lysis by cytotoxic T cells in vitro, and markedly enhanced their tumorigenesis and invasiveness in vivo in the syngeneic hosts as compared with the parental tumor cells that lacked endogenous PD-L. Both effects could be reversed by anti-PD-L1 Ab. Survey of murine tumor lines revealed that all of the myeloma cell lines examined naturally expressed PD-L1. Growth of the myeloma cells in normal syngeneic mice was inhibited significantly albeit transiently by the administration of anti-PD-L1 Ab in vivo and was suppressed completely in the syngeneic PD-1-deficient mice. These results suggest that the expression of PD-L1 can serve as a potent mechanism for potentially immunogenic tumors to escape from host immune responses and that blockade of interaction between PD-1 and PD-L may provide a promising strategy for specific tumor immunotherapy.

Restriction of de novo pyrimidine biosynthesis inhibits Th1 cell activation and promotes Th2 cell differentiation

Leflunomide, an inhibitor of de novo pyrimidine biosynthesis, has recently been introduced as a treatment for rheumatoid arthritis in an attempt to ameliorate inflammation by inhibiting lymphocyte activation. Although the immunosuppressive ability of leflunomide has been well described in several experimental animal models, the precise effects of a limited pyrimidine supply on T cell differentiation and effector functions have not been elucidated. We investigated the impact of restricted pyrimidine biosynthesis on the activation and differentiation of CD4 T cells in vivo and in vitro. Decreased activation of memory CD4 T cells in the presence of leflunomide resulted in impaired generation and outgrowth of Th1 effectors without an alteration of Th2 cell activation. Moreover, priming of naive T cells in the presence of leflunomide promoted Th2 differentiation from uncommitted precursors in vitro and enhanced Th2 effector functions in vivo, as indicated by an increase in Ag-specific Th2 cells and in the Th2-dependent Ag-specific Ig responses (IgG1) in immunized mice. The effects of leflunomide on T cell proliferation and differentiation could be antagonized by exogenous UTP, suggesting that they were related to a profound inhibition of de novo pyrimidine biosynthesis. These results indicate that leflunomide might exert its anti-inflammatory activities in the treatment of autoimmune diseases by preventing the generation of proinflammatory Th1 effectors and promoting Th2 cell differentiation. Moreover, the results further suggest that differentiation of CD4 T cells can be regulated at the level of nucleotide biosynthesis.

CD8(+) T cell tolerance to a tumor-associated antigen is maintained at the level of expansion rather than effector function

CD8+ T cell tolerance to self-proteins prevents autoimmunity but represents an obstacle to generating T cell responses to tumor-associated antigens. We have made a T cell receptor (TCR) transgenic mouse specific for a tumor antigen and crossed TCR-TG mice to transgenic mice expressing the tumor antigen in hepatocytes (gag-TG). TCRxgag mice showed no signs of autoimmunity despite persistence of high avidity transgenic CD8+ T cells in the periphery. Peripheral CD8+ T cells expressed phenotypic markers consistent with antigen encounter in vivo and had upregulated the antiapoptotic molecule Bcl-2. TCRxgag cells failed to proliferate in response to antigen but demonstrated cytolytic activity and the ability to produce interferon gamma. This split tolerance was accompanied by inhibition of Ca(2+) flux, ERK1/2, and Jun kinase phosphorylation, and a block in both interleukin 2 production and response to exogenous interleukin 2. The data suggest that proliferation and expression of specific effector functions characteristic of reactive cells are not necessarily linked in CD8+ T cell tolerance.

CD28 costimulation induces delta opioid receptor expression during anti-CD3 activation of T cells

Previous studies have demonstrated that naive splenic mouse T cells express no or only very low levels of the delta-type opioid receptor (delta OR), but stimulation of mouse splenocytes with Con A results in induction of delta OR mRNA and protein. In this report we have shown that stimulation of highly purified populations of naive mouse T cells with anti-CD3 mAb alone results in T cell activation, as evidenced by sustained IL-2 secretion and cell proliferation, but fails to elicit delta OR expression. However, delta OR expression is induced by costimulation of these very pure T cells with anti-CD3 and anti-CD28 mAbs. The delta OR induction by anti-CD3 and anti-CD28 costimulation was completely blocked by inhibition of phosphatidylinositol 3-kinase with wortmannin. Because phosphatidylinositol 3-kinase activation in T cells is linked to costimulation, these results suggest that induction of delta OR expression during T cell activation is strictly dependent on costimulation. It also appears that costimulatory receptors other than CD28 can provide the signaling required for delta OR expression because delta OR mRNA was induced by Con A stimulation of splenocytes from CD28-deficient mice.

Modulatory effects of garlic extracts on proliferation of T-lymphocytes in vitro stimulated with concanavalin A

Different active components from the garlic (Allium sativum) possess immunomodulatory activity both in vitro and in vivo. However, mechanisms of their actions are not sufficiently elucidated. In this study we examined the effects of garlic aqueous extract (GAE) and garlic ethanolic extract (GEE), prepared from two different garlic powder samples, on proliferation of rat thymocytes and splenocytes in culture, stimulated with concanavalin A (Con A). It has been shown that the extracts from both samples significantly modulate lymphocyte proliferation, triggered by this potent T-cell mitogen, depending on the type and dilutions of extracts and concentrations of Con A. The extracts, alone, were not mitogenic for lymphocytes. Generally, higher concentrations of the extracts showed inhibitory effects, whereas lower concentrations significantly augmented proliferation of lymphocytes. The stimulatory effect of GAE was stronger using splenocytes and suboptimal concentrations of Con A as a consequence of increased interleukin 2 (IL-2) production as well as the expression of IL-2 receptor alpha (IL-2Ralpha). The relationship between these two phenomena was demonstrated using neutralizing anti-IL-2Ralpha monoclonal antibody. The inhibitory effect of GAE correlated with a decrease in IL-2 production, but was not followed by down-regulation of IL-2Ralpha expression. The addition of IL-2 almost completely abolished inhibition of lymphocyte proliferation in the presence of higher concentrations of GAE.

Dendritic cells pulsed with intact Streptococcus pneumoniae elicit both protein- and polysaccharide-specific immunoglobulin isotype responses in vivo through distinct mechanisms

Immature bone marrow-derived myeloid dendritic cells (BMDCs) are induced to undergo phenotypic maturation and secretion of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-12, and IL-10 when pulsed in vitro with intact Streptococcus pneumoniae. After transfer to naive mice, pulsed BMDCs induce immunoglobulin (Ig) isotype responses specific for both protein and polysaccharide pneumococcal antigens, having in common the requirement for viable BMDCs, T cells, and B7-dependent costimulation in the recipient mice. Whereas primary Ig isotype responses to bacterial proteins uniformly require BMDC expression of major histocompatibility complex class II, CD40, and B7, and the secretion of IL-6, but not IL-12, similar requirements for antipolysaccharide Ig responses were only observed for the IgG1 isotype.

Co-stimulatory blockade and tolerance induction in transplantation

Recipients of organ and tissue transplants require lifelong immunosuppression to prevent rejection. Better understanding of the processes culminating in allograft rejection has led to novel approaches to modulating the immune response. Co-stimulatory signals between antigen-presenting and -responding cells are essential for a normal alloimmune response, and blockade of these pathways during initial graft-host interaction may be used to ameliorate or prevent a destructive response from proceeding. A large number of experimental studies now support this concept, and early clinical trials have been initiated. Despite some early difficulties and many unanswered questions, co-stimulatory blockade has major potential as a future immune-modulating mechanism for use in clinical transplantation.

Costimulation and endogenous MHC ligands contribute to T cell recognition

To initiate an immune response, key receptor-ligand pairs must cluster in "immune synapses" at the T cell-antigen-presenting cell (APC) interface. We visualized the accumulation of a major histocompatibility complex (MHC) class II molecule, I-E(k), at a T cell-B cell interface and found it was dependent on both antigen recognition and costimulation. This suggests that costimulation-driven active transport of T cell surface molecules helps to drive immunological synapse formation. Although only agonist peptide-MHC class II (agonist pMHC class II) complexes can initiate T cell activation, endogenous pMHC class II complexes also appeared to accumulate. To test this directly, we labeled a "null" pMHC class II complex and found that, although it lacked major TCR contact residues, it could be driven into the synapse in a TCR-dependent manner. Thus, low-affinity ligands can contribute to synapse formation and T cell signaling.

CTLA-4/CD 28 region polymorphisms in children from families with autoimmune hepatitis

Susceptibility to autoimmune hepatitis is associated with particular human leucocyte antigen class II alleles. However, non-HLA genetic factors are likely to be required for development of the disease. Among the candidate genes, the cytotoxic T-lymphocyte antigen 4 (CTLA-4) and CD28 genes, located on chromosome 2q33 in humans, encode a cell surface molecule playing a dominant role in the regulation of T-cell activation. The CTLA-4 and CD28 polymorphisms were investigated in children from 32 families with autoimmune hepatitis (AIH). The transmission/disequilibrium test revealed increased transmission of the (AT)8 (dinucleotide repeat) and A (exon 1) alleles of CTLA-4 gene from heterozygous parents to affected offspring (87.5% and 83.5%) with type 1 AIH, compared with unaffected offspring (50.0% for both, p = 0.009 and 0.02, respectively). In contrast, no deviation in transmission for CTLA-4 polymorphisms was found between type 2 AIH patients and unaffected offspring. No evidence for association was found between CD28 gene polymorphism or D2S72 genetic marker and both types of AIH. This study identified the CTLA-4 gene polymorphism as a non-HLA determinant that predisposes to AIH type 1 in children. The genetic heterogeneity seen in the present study provides a new argument in favor of pathogenic differences between type 1 and type 2 AIH.

CD4 ligation promotes the IL-4-independent development of IL-4-producing clones from naive CD4(+) T cells

The signals that trigger IL-4-independent IL-4 synthesis by conventional CD4(+) T cells are not yet defined. In this study, we show that coactivation with anti-CD4 mAb can stimulate single naive CD4(+) T cells to form IL-4-producing clones in the absence of APC and exogenous IL-4, independently of effects on proliferation. When single CD4(+) lymph node cells from C57BL/6 mice were cultured with immobilized anti-CD3epsilon mAb and IL-2, 65-85% formed clones over 12-14 days. Coimmobilization of mAb to CD4, CD11a, and/or CD28 increased the size of these clones but each exerted different effects on their cytokine profiles. Most clones produced IFN-gamma and/or IL-3 regardless of the coactivating mAb. However, whereas 0-6% of clones obtained with mAb to CD11a or CD28 produced IL-4, 10-40% of those coactivated with anti-CD4 mAb were IL-4 producers. A similar response was observed among CD4(+) cells from BALB/c mice. Most IL-4-producing clones were derived from CD4(+) cells of naive (CD44(low) or CD62L(high)) phenotype and the great majority coproduced IFN-gamma and IL-3. The effect of anti-CD4 mAb on IL-4 synthesis could be dissociated from effects on clone size since anti-CD4 and anti-CD11a mAb stimulated formation of clones of similar size which differed markedly in IL-4 production. Engagement of CD3 and CD4 in the presence of IL-2 is therefore sufficient to induce a substantial proportion of naive CD4(+) T cells to form IL-4-producing clones in the absence of other exogenous signals, including IL-4 itself.

Targeted delivery of anti-CTLA-4 antibody downregulates T cell function in vitro and in vivo

CTLA-4 is a T cell surface molecule that binds to the costimulatory molecules CD80 and CD86 on antigen-presenting cells and downregulates T cell function. Therefore, we wanted to test whether antigen-specific activated T cells could be inhibited through directed CTLA-4 signaling using a bispecific antibody (BiAb) capable of simultaneously binding to CTLA-4 and a tissue-specific antigen. The BiAb was prepared by linking two separate monoclonal antibodies against CTLA-4 and the thyroid-stimulating hormone receptor (TSHR). The mouse B cell lymphoma line M12 (H2(d)) was used to induce alloreactive T cells in CBA/J mice (H2(k)); M12 cells stably transfected with the cDNA encoding murine TSHR (mM12) were used to restimulate the alloresponse in vitro. Results of assays for in vitro T cell proliferation, IL-2 production, and cytotoxicity in the presence of BiAb demonstrated that the BiAb could inhibit the T cell alloresponse when stimulated with mM12 cells but not with M12 cells. This effect was dependent on binding of TSHR-bound BiAb to CTLA-4, since the addition of soluble CTLA-4-Ig blocked the inhibitory effect. Injection of mM12 cells, along with the BiAb, not with antibodies against TSHR or CTLA-4 either separately or together, into CBA/J mice (H2(k)) downregulated alloreactive T cell responses. Our study demonstrated that the presence of CTLA-4 signaling molecules on the surface of target cells can protect those cells from immune attack by antigen-specific T cells and suggested that a similar approach could have potential therapeutic value in transplant rejection and tissue-specific autoimmune diseases.