Cooperation between T and B cells reinforce the establishment of bone metastases in a mouse model of breast cancer

Immune cells educated by the primary breast tumor and their secreted factors support the formation of bone pre-metastatic niche. Indeed, we showed that RANKL+ CD3+ T cells, specific for the 4T1 mammary carcinoma cell line, arrive at the bone marrow before metastatic cells and set the pre-metastatic niche. In the absence of RANKL expressed by T cells, there is no pre-metastatic osteolytic disease and bone metastases are completely blocked. Adding to the role of T cells, we have recently demonstrated that dendritic cells assist RANKL+ T cell activities at bone pre-metastatic niche, by differentiating into potent bone resorbing osteoclast-like cells, keeping their antigen-presenting cell properties, providing a positive feedback loop to the osteolytic profile. Here we are showing that bone marrow-derived CD19+ B cells, from 4T1 tumor-bearing mice, also express the pro-osteoclastogenic cytokine receptor activator of NFκB ligand (RANKL). Analysis of trabecular bone mineral density by conventional histomorphometry and X-ray microtomography (micro-CT) demonstrated that B cells expressing RANKL cooperate with 4T1-primed CD3+ T cells to induce bone loss. Moreover, RANKL expression by B cells depends on T cells activity, since experiments performed with B cells derived from 4T1 tumor-bearing nude BALB/c mice resulted in the maintenance of trabecular bone mass instead of bone loss. Altogether, we believe that 4T1-primed RANKL+ B cells alone are not central mediators of bone loss in vivo but when associated with T cells induce a strong decrease in bone mass, accelerating both breast cancer progression and bone metastases establishment. Although several studies performed in different pathological settings, showed that B cells, positively and negatively impact on osteoclastogenesis, due to their capacity to secret pro or anti-osteoclastogenic cytokines, as far as we know, this is the first report showing the role of RANKL expression by B cells on breast cancer-derived bone metastases scenario.

Programmed cell death protein 1 is a marker for neoadjuvant chemotherapy response in triple-negative breast cancer

OBJECTIVE

Tumor-infiltrating lymphocytes are detectable in up to 75% of triple-negative breast cancer. The composition of these infiltrates may influence prognosis and is not known regarding regulatory or effector lymphocytes. The objectives of this study were to describe and quantify the composition of the tumor-infiltrating lymphocytes before and after chemotherapy (neoadjuvant chemotherapy) and to evaluate their association with complete pathological response and overall survival.

METHODS

This was a retrospective observational study. Clinical and pathological data from 38 triple-negative breast cancer patients treated with neoadjuvant chemotherapy at the University Hospital (HUCFF/UFRJ), between November 2004 and November 2018, were analyzed. The Stromal tumor-infiltrating lymphocytes (Stromal tumor-infiltrating lymphocytes) have been identified on hematoxylin and eosin-stained sections according to the guidelines of the "International tumor-infiltrating lymphocytes Working Group." Immunohistochemistry studies were performed to identify T-cell subsets (i.e., CD3, CD4, CD8, and FOXP3) and T-cell exhaustion (i.e., programmed cell death protein 1).

RESULTS

Statistically significant changes in stromal tumor-infiltrating lymphocyte categories were observed before and post-neoadjuvant chemotherapy, with 32% of intermediate cases becoming high. The correlation between pre-neoadjuvant chemotherapy stromal tumor-infiltrating lymphocytes and pathological response, pre-neoadjuvant chemotherapy and post-neoadjuvant chemotherapy, and stromal tumor-infiltrating lymphocytes and overall survival was not statistically significant. However, we noticed an increase of cells that favor the antitumor activity (i.e., CD3, CD8, and CD8/FOXP3 ratio) and decreased levels of cells inhibiting tumor activities (i.e., FOXP3 and programmed cell death protein 1) post-neoadjuvant chemotherapy. Importantly, programmed cell death protein 1 expression pre-neoadjuvant chemotherapy showed an association with pathological response.

CONCLUSION

In this study, we observed that chemotherapy significantly increases stromal tumor-infiltrating lymphocytes, CD8 T cells, as well as CD8/FoxP3 ratio. Most importantly, programmed cell death protein 1 expression before neoadjuvant chemotherapy positively correlates with pathological response suggesting the use of programmed cell death protein 1 as a prognostic marker before neoadjuvant chemotherapy.

Central nervous system commitment in Chagas disease

The involvement of the central nervous system (CNS) during human acute and chronic Chagas disease (CD) has been largely reported. Meningoencephalitis is a frequent finding during the acute infection, while during chronic phase the CNS involvement is often accompanied by behavioral and cognitive impairments. In the same vein, several studies have shown that rodents infected with Trypanosoma cruzi (T. cruzi) display behavior abnormalities, accompanied by brain inflammation, in situ production of pro-inflammatory cytokines and parasitism in diverse cerebral areas, with involvement of microglia, macrophages, astrocytes, and neurons. However, the mechanisms used by the parasite to reach the brain remain now largely unknown. Herein we discuss the evidence unravelling the CNS involvement and complexity of neuroimmune interactions that take place in acute and chronic CD. Also, we provide some clues to hypothesize brain infections routes in human and experimental acute CD following oral infection by T. cruzi, an infection route that became a major CD related public health issue in Brazil.

CD8+ T cells from experimental in situ breast carcinoma interfere with bone homeostasis

Before bone colonization, immune cells primed by breast primary tumor cells actively modify the bone microenvironment, disturbing the complex and tightly homeostatic signaling network regulated by osteoblasts and osteoclasts. Indeed, we have shown that RANKL⁺ CD4⁺ T cells specific for the 4T1 mammary carcinoma cell line, arrive at the bone marrow (BM) before metastatic cells and set the pre-metastatic niche. In the absence of RANKL expressed by T cells, there is no pre-metastatic osteolytic disease and bone metastases are blocked. Adding to the role of T cells, we have recently demonstrated that dendritic cells (DCs) provide a positive feedback loop to the osteolytic profile induced by the metastatic tumor. In this setting, DCs are able to differentiate into potent bone resorbing osteoclast-like cells keeping their antigen-presenting cell (APC) properties to maintain RANKL⁺ CD4⁺ Th17 T cells activities, via IL-23 expression. Here we show that 67NR non-metastatic tumor cells, a sibling of 4T1 tumor cell line, induce an increase in trabecular bone mass on day 11 post-tumor implant. This observation was associated with an expansion of the osteoblastic lineage cells accompanied by a reduction of osteoclasts numbers. Moreover, BM derived CD8⁺ T cells from 67NR tumor-bearing mice, express an anti-osteoclastogenic cytokine milieu enriched by IFN-γ, IL-10 and producing low levels of RANKL. The frequency of BM derived CD8⁺ FoxP3⁺ regulatory T cells, known as potent suppressors of osteoclastogenesis both in vitro and in vivo, was also increased in such animals. This milieu was capable to suppress 4T1 tumor-specific CD4⁺ T cells phenotype in vivo and in vitro and strongly inhibited bone metastases establishment, restoring trabecular bone mass volume. We concluded that the 67NR⁺ tumor derived CD8⁺ T cells phenotypes, either contributing to bone homeostasis and/or control of 4T1 breast tumor pre-metastatic disease, interfere with osteoclasts and osteoblasts activities inside BM. Our study highlights the opposing roles of subverted tumor CD4⁺ and CD8⁺ T cell subtypes in directing breast cancer progression and bone metastases establishment. For non-metastatic tumors, the role of T cells regarding bone remodeling has never been addressed before. As far as we know, this is the first description that an in situ carcinoma can modify distant sites. In the case showed here, modification of the distant bone site disfavors pre-metastatic bone niche formation.

Dendritic cells development into osteoclast-type APCs by 4T1 breast tumor T cells milieu boost bone consumption

Bone metastases occur in 70% of patients with advanced breast cancer, causing severe morbidity and increased mortality due to osteolytic lesions driven by osteoclasts (OCs) inside the bone marrow (BM) microenvironment. A reciprocal vicious cycle between bone remodeling system and the tumor itself is established by the release of growth factors stored in the mineralized matrix, which in turn feed the tumor, changing tumor behavior and growth. However, BM is not a passive host microenvironment for circulating tumor cells, but instead can be actively modified by the primary tumor before metastatic spread occurs. Indeed, we have shown that T cells specific for the 4T1 mammary carcinoma cell line, are characteristically RANKL⁺ IL-17F⁺ CD4⁺ T cells. Those cells arrive in the BM before metastatic cells and set the pre-metastatic niche. In the absence of T cell derived RANKL, there is no pre-metastatic osteolytic disease and bone metastases do not take place. Recently, dendritic cells (DCs), the main T cell partner at the beginning of the immune response, came into the spotlight as a potential source of OCs progenitors under inflammatory conditions. Regarding bone metastasis, nothing is currently known about DCs plasticity or even its partnership with tumor induced T cells for BM pre-metastatic niche formation. Here, we show that splenic CD11c⁺ DCs stimulated with 4T1 conditioned media (CM) efficiently differentiated into mature and activated multinucleated giant cells (DC-OC) expressing TRAP and IL-23 cytokine. More important, 4T1 CM derived DC-OCs build a positive loop which amplifies the osteolytic phenomena by maintaining the RANKL⁺ Th17 T cells and by its own osteoclastic activity. In conclusion, our results indicate that differentiation of OCs from DCs may be achievable in the bone pre osteolytic disease context representing an alternative OC differentiation pathway. Besides being induced by high levels of T cells pro osteoclastogenic cytokines, especially by RANKL, DC-OC keep a positive feedback loop towards osteolysis, maintaining the pro-osteoclastogenic T cell phenotype in the BM.

Class I HLA Allele Predicted Restricted Antigenic Coverages for Spike and Nucleocapsid Proteins Are Associated With Deaths Related to COVID-19

The world is dealing with one of the worst pandemics ever. SARS-CoV-2 is the etiological agent of COVID-19 that has already spread to more than 200 countries. However, infectivity, severity, and mortality rates do not affect all countries equally. Here we consider 140 HLA alleles and extensively investigate the landscape of 3,723 potential HLA-I A and B restricted SARS-CoV-2-derived antigens and how 37 countries in the world are predicted to respond to those peptides considering their HLA-I distribution frequencies. The clustering of HLA-A and HLA-B allele frequencies partially separates most countries with the lowest number of deaths per million inhabitants from the other countries. We further correlated the patterns of in silico predicted population coverage and epidemiological data. The number of deaths per million inhabitants correlates to the predicted antigen coverage of S and N derived peptides and its module is influenced if a given set of frequent or rare HLA alleles are analyzed in a given population. Moreover, we highlighted a potential risk group carrying HLAs associated with an elevated number of deaths per million inhabitants. In addition, we identified three potential antigens bearing at least one amino acid of the four-length insertion that differentiates SARS-CoV-2 from previous coronavirus strains. We believe these data can contribute to the search for peptides with the potential to be used in vaccine strategies considering the role of herd immunity to hamper the spread of the disease. Importantly, to the best of our knowledge, this work is the first to use a populational approach in association with COVID-19 outcome.

Abstract P2-04-15: Osteoclasts derived from dendritic cells by 4T1 T cells millieu maintain antigen presenting capability and osteolytic activity

This abstract was withdrawn by the authors.

Macrophage-dependent IL-1β production induces cardiac arrhythmias in diabetic mice

Diabetes mellitus (DM) encompasses a multitude of secondary disorders, including heart disease. One of the most frequent and potentially life threatening disorders of DM-induced heart disease is ventricular tachycardia (VT). Here we show that toll-like receptor 2 (TLR2) and NLRP3 inflammasome activation in cardiac macrophages mediate the production of IL-1β in DM mice. IL-1β causes prolongation of the action potential duration, induces a decrease in potassium current and an increase in calcium sparks in cardiomyocytes, which are changes that underlie arrhythmia propensity. IL-1β-induced spontaneous contractile events are associated with CaMKII oxidation and phosphorylation. We further show that DM-induced arrhythmias can be successfully treated by inhibiting the IL-1β axis with either IL-1 receptor antagonist or by inhibiting the NLRP3 inflammasome. Our results establish IL-1β as an inflammatory connection between metabolic dysfunction and arrhythmias in DM.

G-CSF-Induced Suppressor IL-10+ Neutrophils Promote Regulatory T Cells That Inhibit Graft-Versus-Host Disease in a Long-Lasting and Specific Way

Acute graft-versus-host disease (aGVHD) is the main complication of allogeneic hematopoietic stem cell transplantation, and many efforts have been made to overcome this important limitation. We showed previously that G-CSF treatment generates low-density splenic granulocytes that inhibit experimental aGVHD. In this article, we show that aGVHD protection relies on incoming IL-10⁺ neutrophils from G-CSF-treated donor spleen (G-Neutrophils). These G-Neutrophils have high phagocytic capacity, high peroxide production, low myeloperoxidase activity, and low cytoplasmic granule content, which accounts for their low density. Furthermore, they have low expression of MHC class II, costimulatory molecules, and low arginase1 expression. Also, they have low IFN-γ, IL-17F, IL-2, and IL-12 levels, with increased IL-10 production and NO synthase 2 expression. These features are in accordance with the modulatory capacity of G-Neutrophils on regulatory T cell (Treg) generation. In vivo, CD25⁺ Treg depletion shortly after transplantation with splenic cells from G-CSF-treated donors blocks suppression of aGVHD, suggesting Treg involvement in the protection induced by the G-Neutrophils. The immunocompetence and specificity of the semiallogeneic T cells, long-term after the bone marrow transplant using G-Neutrophils, were confirmed by third-party skin graft rejection; importantly, a graft-versus-leukemia assay showed that T cell activity was maintained, and all of the leukemic cells were eliminated. We conclude that G-CSF treatment generates a population of activated and suppressive G-Neutrophils that reduces aGVHD in an IL-10- and Treg-dependent manner, while maintaining immunocompetence and the graft versus leukemia effect.

A T Cell View of the Bone Marrow

The majority of T cells present in the bone marrow (BM) represent an activated/memory phenotype and most of these, if not all, are circulating T cells. Their lodging in the BM keeps them activated, turning the BM microenvironment into a “memory reservoir.” This article will focus on how T cell activation in the BM results in both direct and indirect effects on the hematopoiesis. The hematopoietic stem cell niche will be presented, with its main components and organization, along with the role played by T lymphocytes in basal and pathologic conditions and their effect on the bone remodeling process. Also discussed herein will be how “normal” bone mass peak is achieved only in the presence of an intact adaptive immune system, with T and B cells playing critical roles in this process. Our main hypothesis is that the partnership between T cells and cells of the BM microenvironment orchestrates numerous processes regulating immunity, hematopoiesis, and bone remodeling.

Abstract P2-05-24: OPG+ bone marrow B cells induced by non-metastatic tumors inhibit the pre-metastatic bone niche induced by T cells

Using the 4T1 model of experimental breast cancer we had recently shown that cancer induced bone disease starts before metastatic colonization and is mediated by RANKL expressed by tumor specific T cells. The role of anti-tumor B cell immune response in the context of cancer induced bone disease has never been investigated. There is evidence in the literature that B cells are good prognostic markers for metastatic breast cancer. B cells have an intimate relationship with bone cells as they differentiate from HSC present on endosteal surfaces; cross-talk with skeletal system through the RANK-RANKL-OPG signaling axis; and produce OPG, a decoy receptor of RANKL.

Here we used the BALB/c derived 4T1 (metastatic) and 67NR (non-metastatic) sibling cell lines of mammary mouse carcinomas. By day 7, 14 and 21 after tumor injection, B220+ BM B cells from 67NR+ animals produce high amounts of OPG in vitro in contrast to B220+ BM B cells of 4T1+ mice. In vitro, BM B cells from 67NR+ mice, but not from 4T1+, could inhibit the RANKL dependent, anti-4T1 T cell mediated-OC differentiation ascertained by TRAP enzymatic activity, morphology and osteolytic disk assay.

Transference of BM B cells from 67NR+ mice together with 4T1 tumor cells to BALB/c mice led to inhibition of osteoclastogenesis, increased numbers of bone lining cells and mesenchyme stem cell. Besides acting directly on the bone remodeling system, these B cells also modulated T cell activity evidenced by diminished RANKL and IL-17F production.

All the anti-osteolytic and pro-osteogenic activity of B cells modulate and inhibits the pre-metastatic niche formation. Indeed transference of such cells to 4T1 animals inhibited LN and BM metastatic colonization.

We conclude that 67NR induced OPG+ B cells can inhibit pro-osteoclastic / pre-metastatic activity of tumor induced T cells, favoring a bone metastasis free-phenotype. These findings have implications, not only for the understanding of the direct contribution of B cells in the control of bone metastasis but also it might be a promising prognostic tool for predicting cancer-induced bone metastasis.

Citation Format: Bonomo A, Monteiro AC, Leal AC, Fontão AP, Spinetti E, Balduino A. OPG+ bone marrow B cells induced by non-metastatic tumors inhibit the pre-metastatic bone niche induced by T cells. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-05-24.

Abstract B39: Neutrophils G-CSF stimulated promotes specific protection against graft vs. host disease and keeps the graft vs. leukemia effect

Allogeneic hematopoietic stem cell transplantation (HSCT) is used to treat a series of hematological diseases. While the presence of T cells mediates the graft-versus-leukemia (GVL) effect and improves engraftment, it is also responsible for the graft-versus-host disease (GVHD), which is the main barrier of HSCT. Patients transplanted with cells from G-CSF treated donors show an unexpected low rate of acute GVHD given the high numbers of T cells present. We have previously shown that blood from G-CSF treated donors have high numbers of inhibitory granulocytes. Experimentally these granulocytes are able to prevent aGVHD in a semi-allogeneic mouse model. Here, our goal is to characterize the granulocytes and its mechanism of action. When we compare this granulocytes from the spleens of 5 day G-CSF treated donors and its untreated control, we observed on flow cytometry that the percentage of this granulocytes/neutrophils Ly6G+ increases from about 2% to about 20%. These cells have some differences among themselves after treatment as increased burst oxidative (measured by DHR) and phagocytosis of E.coli, as well as differences in the pattern of expression of some important surface molecules, such as MHC-II. Levels of myeloperoxidase are lower after treatment with G-CSF, and we confirmed by transmission electron microscopy that these neutrophils have a degranulated profile, with 83% fewer cytoplasmic granules than controls. Indeed, the spleens from 5 day G-CSF treated donors together with control bone marrow cells (G-B6) injected into irradiated F1(B6XBALB/c) mice shows survival rate of 100%, against 10% in non-G-B6 transplants. This protection depends on Gr1+ cells and presents milder pathological and clinical manifestations in gastrointestinal mucosa, skin and liver. However, when these G-B6 neutrophils are from IL-10 KO mice, protection is abolished both in survival curve and in clinical score. Surprisingly, 25 days after transplantation the percentage of the subtype of T regulatory Foxp3+ cells in protected chimeras is increased in all lymphoid organs analyzed and this can be associated with the long term specific tolerance observed. Finally, the anti-tumoral effect in G-B6 chimeras is as potent as in the B6 control chimera and this effect was maintained for more than 20 weeks after HSCT. So we can conclude that treatment with G-CSF generates degranulated neutrophils that reduce GVHD in an IL-10 dependent manner while keeping GVL effect opening a promising road in the prevention of human aGVHD. Financial Support: FAF, INCA, Swiss Bridge, INCT Cancer, FAPERJ, CNPQ, CAPES, Fiocruz.

Citation Format: Suelen Martins Perobelli, Ana Carolina Terra Mercadante, Triciana Gonçalves-Silva, Rômulo Galvani, Antônio Pereira-Neves, Marlene Benchimol, Alberto Nobrega, Adriana Bonomo. Neutrophils G-CSF stimulated promotes specific protection against graft vs. host disease and keeps the graft vs. leukemia effect. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B39.

Plasticity of neutrophils reveals modulatory capacity

Neutrophils are widely known as proinflammatory cells associated with tissue damage and for their early arrival at sites of infection, where they exert their phagocytic activity, release their granule contents, and subsequently die. However, this view has been challenged by emerging evidence that neutrophils have other activities and are not so short-lived. Following activation, neutrophil effector functions include production and release of granule contents, reactive oxygen species (ROS), and neutrophil extracellular traps (NETs). Neutrophils have also been shown to produce a wide range of cytokines that have pro- or anti-inflammatory activity, adding a modulatory role for this cell, previously known as a suicide effector. The presence of cytokines almost always implies intercellular modulation, potentially unmasking interactions of neutrophils with other immune cells. In fact, neutrophils have been found to help B cells and to modulate dendritic cell (DC), macrophage, and T-cell activities. In this review, we describe some ways in which neutrophils influence the inflammatory environment in infection, cancer, and autoimmunity, regulating both innate and adaptive immune responses. These cells can switch phenotypes and exert functions beyond cytotoxicity against invading pathogens, extending the view of neutrophils beyond suicide effectors to include functions as regulatory and suppressor cells.

Disease severity and mortality can be independently regulated in a mouse model of experimental graft versus host disease

Graft versus host disease (GVHD) is the major limitation of allogeneic hematopoietic stem cell transplantation (HSCT) presenting high mortality and morbidity rates. However, the exact cause of death is not completely understood and does not correlate with specific clinical and histological parameters of disease. Here we show, by using a semi-allogeneic mouse model of GVHD, that mortality and morbidity can be experimentally separated. We injected bone marrow-derived dendritic cells (BMDC) from NOD2/CARD15-deficient donors into semi-allogeneic irradiated chimaeras and observed that recipients were protected from death. However, no protection was observed regarding clinical or pathological scores up to 20 days after transplantation. Protection from death was associated with decreased bacterial translocation, faster hematologic recovery and epithelial integrity maintenance despite mononuclear infiltration at day 20 post-GVHD induction with no skew towards different T helper phenotypes. The protected mice recovered from aGVHD and progressively reached scores compatible with healthy animals. Altogether, our data indicate that severity and mortality can be separate events providing a model to study transplant-related mortality.

Abstract 2590: Oral combined therapy with probiotics and alloantigen induces B cell dependent long lasting specific tolerance

Background. Allogeneic hematopietic stem cell transplantation (aHSCT) is widely used for the treatment of hematologic malignancies. Although aHSCT provides a good response against the malignant cells (GVL), it also leads to the development of graft-versus-host disease (GVHD), a severe disease with high mortality and morbidity rates. Therapy for GVHD is commonly based on non-specific immunosupression of the transplanted recipient, resulting in the concomitant inhibition of the GVL effect. Material and Methods. Here we propose an alternative approach to specifically suppress GVHD, while sparing the GVL, based on oral treatment of transplant donors with recipient antigens, associated with the intake of probiotic Lactococcus lactis as tolerogenic adjuvant (combined therapy). Results. We show that treatment of C57Bl/6 donor mice with combined therapy before the transplant protects the recipients F1 (C57Bl/6XBAL/c) mice from clinical and pathological manifestations of disease, resulting in 100% survival rate. Importantly, the animals keep the immunological competence maintaining the GVL response as well as the response to third party antigens. The protection is specific, long lasting and dependent on donor IL-10 sufficient B cells activity which induces regulatory T cells in the host. Conclusion. These data suggest that combined therapy is a promising strategy for prevention of GVHD with preservation of GVL, opening new possibilities to treat human patients subjected transplantation.

Note: This abstract was not presented at the meeting.

Citation Format: Ana Carolina T. Mercadante, Suelen Perobelli, Ana Paula G. Alves, Triciana Gonçalves-Silva, Wallace Mello, Ana C Gomes-Santos, Anderson Miyoshi, Ana Maria C. Faria, Adriana Bonomo. Oral combined therapy with probiotics and alloantigen induces B cell dependent long lasting specific tolerance. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2590. doi:10.1158/1538-7445.AM2014-2590

Cigarette smoke condensate affects monocyte interaction with endothelium

OBJECTIVE

Circulating monocytes adhere to the endothelium and migrate into the intima contributing to atherosclerotic plaque growth. Cigarette smoke is a risk factor for atherosclerosis, but it is not completely known how it affects monocyte behavior in atherogenesis.

METHODS

We studied the effects of cigarette smoke condensate (CSC) on human monocytes (HM) chemotaxis and transmigration through an endothelial cell (EC) monolayer.

RESULTS

Pre-treatment with CSC caused a decrease in HM chemotaxis and transmigration (-55% and -18% vs control, p < 0.05, respectively), paralleled by a reduced expression of Rac 1 GTPase. On the contrary, direct exposure of both HM and EC to CSC increased (+23% vs control, p < 0.05) HM transmigration, paralleled by a strong stimulation of VCAM1 and ICAM1 expression by ECs, and by a slight increase in monocyte integrin expression. An enhancement of monocyte transmigration was obtained after the exposure of both HM and EC to medium conditioned by HM previously incubated with CSC (+265% vs control, p < 0.001). CSC showed a stimulatory effect on the expression by HM of TLR4, MCP1, IL8, IL1beta, and TNFalfa, which was ablated by pre treatment with PDTC. Incubation with neutralizing antibodies against both MCP1 or IL8 completely abolished the CSC-conditioned medium induced HM transmigration.

CONCLUSIONS

CSC induces HM to release chemotactic factor(s), which amplify the recruitment and transmigration of inflammatory cells through EC, but CSC may also reduce HM migratory capacity. Therefore, exposure to CSC affects monocyte behavior and interaction with the endothelium, thus potentially facilitating and/or further aggravating the atherogenic process.

Oral combined therapy with probiotics and alloantigen induces B cell-dependent long-lasting specific tolerance

Allogeneic hematopietic stem cell transplantation (aHSCT) is widely used for the treatment of hematologic malignancies. Although aHSCT provides a good response against the malignant cells (graft-versus-leukemia [GVL]), it also leads to the development of graft-versus-host disease (GVHD), a severe disease with high mortality and morbidity rates. Therapy for GVHD is commonly based on nonspecific immunosupression of the transplanted recipient, resulting in the concomitant inhibition of the GVL effect. In this study, we propose an alternative approach to specifically suppress GVHD while sparing the GVL, based on oral treatment of transplant donors with recipient Ags, associated with the intake of probiotic Lactococcus lactis as tolerogenic adjuvant (combined therapy). We show that treatment of C57BL/6 donor mice with combined therapy before the transplant protects the recipients F1 (C57BL/6 × BAL/c) mice from clinical and pathological manifestations of disease, resulting in 100% survival rate. Importantly, the animals keep the immunological competence maintaining the GVL response as well as the response to third-party Ags. The protection is specific, long lasting and dependent on donor IL-10-sufficient B cells activity, which induces regulatory T cells in the host. These data suggest that combined therapy is a promising strategy for prevention of GVHD with preservation of GVL, opening new possibilities to treat human patients subjected to transplantation.

T cells induce pre-metastatic osteolytic disease and help bone metastases establishment in a mouse model of metastatic breast cancer

Bone metastases, present in 70% of patients with metastatic breast cancer, lead to skeletal disease, fractures and intense pain, which are all believed to be mediated by tumor cells. Engraftment of tumor cells is supposed to be preceded by changes in the target tissue to create a permissive microenvironment, the pre-metastatic niche, for the establishment of the metastatic foci. In bone metastatic niche, metastatic cells stimulate bone consumption resulting in the release of growth factors that feed the tumor, establishing a vicious cycle between the bone remodeling system and the tumor itself. Yet, how the pre-metastatic niches arise in the bone tissue remains unclear. Here we show that tumor-specific T cells induce osteolytic bone disease before bone colonization. T cells pro-metastatic activity correlate with a pro-osteoclastogenic cytokine profile, including RANKL, a master regulator of osteoclastogenesis. In vivo inhibition of RANKL from tumor-specific T cells completely blocks bone loss and metastasis. Our results unveil an unexpected role for RANKL-derived from T cells in setting the pre-metastatic niche and promoting tumor spread. We believe this information can bring new possibilities for the development of prognostic and therapeutic tools based on modulation of T cell activity for prevention and treatment of bone metastasis.

An Ectopic Stromal Implant Model for Hematopoietic Reconstitution and in Vivo Evaluation of Bone Marrow Niches

In adults, hematopoiesis takes places in the bone marrow, where specialized niches containing mesenchymal nonhematopoietic cells (stroma) harbor the hematopoietic stem cell (HSC). These niches are responsible and essential for the maintenance of HSCs. Attempts to expand HSCs fail to keep the general properties of stem cells, which depend on several niche components difficult to reproduce in in vitro culture systems. Here, we describe a methodology for in vivo study of hematopoietic stroma. We use stroma-loaded macroporous microcarriers implanted in the subcutaneous tissue of experimental animals and show that the ectopic stroma implant (ESI) is able to support hematopoiesis. Moreover, lethally irradiated mice can be rescued by ESI preloaded with HSCs, showing that they function as an ectopic bone marrow. ESI is also shown as a good system to study the role of different niche components. As an example, we used stromas lacking connexin 43 (Cx43) and confirm the importance of this molecule in the maintenance of the HSC niche in vivo. We believe ESI can work as an ectopic bone marrow allowing in vivo testing of different niches components and opening new avenues for the treatment of a variety of hematologic conditions particularly when stromal cell defects are the main cause of disease.

Prolonged acceptance of skin grafts induced by B cells places regulatory T cells on the histopathology scene

The participation of regulatory T (Treg) cells in B cell-induced T cell tolerance has been claimed in different models. In skin grafts, naive B cells were shown to induce graft tolerance. However, neither the contribution of Treg cells to B cell-induced skin tolerance nor their contribution to the histopathological diagnosis of graft acceptance has been addressed. Here, using male C57BL/6 naive B cells to tolerize female animals, we show that skin graft tolerance is dependent on CD25⁺ Treg cell activity and independent of B cell-derived IL-10. In fact, B cells from IL-10-deficient mice were able to induce skin graft tolerance while Treg depletion of the host inhibited 100% graft survival. We questioned how Treg cell-mediated tolerance would impact on histopathology. B cell-tolerized skin grafts showed pathological scores as high as a rejected skin from naive, non-tolerized mice due to loss of skin appendages, reduced keratinization and mononuclear cell infiltrate. However, in tolerized mice, 40% of graft infiltrating CD4⁺ cells were FoxP3⁺ Treg cells with a high Treg:Teff (effector T cell) ratio (6:1) as compared to nontolerized mice where Tregs comprise less than 8% of total infiltrating CD4 cells with a Treg:Teff ratio below 1:1. These results render Treg cells an obligatory target for histopathological studies on tissue rejection that may help to diagnose and predict the outcome of a transplanted organ.

P1-01-02: T Cell Is a Key Player in the Establishment of Cancer Associated Pre-Metastatic Bone Disease

Syngeneic mouse models of malignant diseases have the important advantage of allowing studies to be carried out in immunocompetent animals. In this work, the 4T1(metastatic) and 67NR (non-metastatic) sibling cell lines of mammary mouse carcinomas, syngeneic to BALB/c mouse were used to study tumor specific immune response and its impact on bone disease.

By day 11 after tumor injection, in the absence of metastasis, pro-osteoclastogenic cytokines IL17F, TNFα, IL-1β and RANKL were present in the BM of 4T1+ mice in contrast to the virtual absence of these in the BM of 67NR+ animals.

More important, imaging studies (histomorphometry and microCT) showed that trabecular bone mass is close to maximum loss (around 50%) already by day 11, in the absence of metastasis. These results support the possibility of T cell involvement in pre-metastatic lesion. Indeed, in vitro, BM T cells from 4T1+ mice, but not from 67NR+, could induce OC differentiation in response to tumor antigens ascertained by TRAP enzymatic activity, morphology and osteolytic disk assay. In vivo transfer experiments showed that T cells from 4T1+ mice (Day 11), when transferred into nude mice produce 3 times more IL17F and 4 times more RANKL than donor 67NR+ T cells. Moreover, trabecular bone at day 14 after transfer of 4T1+T cells was already 30% that of normal nude mice in contrast to 100% from 67NR+ T cells. Of note is the fact that these activities are achieved in the absence of the metastatic 4T1 tumor in the nude host, but challenged with either 67NR or protein antigen extract.

To address the role of T cell derived IL17F and RANKL, T cells from 4T1 bearing mice (day 11) were silenced with shRNA specific for each of these cytokines and transferred into nude mice. Animals were challenged with soluble tumor antigen. Silencing IL17F had no effect over bone loss. However, RANKL silencing completely inhibited osteolytic lesions. Together, these results indicate that RANKL in T cells mediate the osteolytic lesions and that cancer induced bone disease can be metastasis independent.

Since osteolytic lesions are believed to be important to feed the tumor with growth factors in a vicious cycle established in the metastatic niche, we asked if T cells could be preparing the pre-metastatic niche. When 4T1 cells are injected into athymic nude mice, bone metastasis is not observed up to day 24, while by day 20 it is already present in euthymic BALB/c animals, indicating that T cells are critical to prepare the seeding soil for tumor cells within the bone. We are currently investigating the role of T cells in the establishment of metastasis at later time points as well as in the primary tumor growth. Our results strongly suggest that tumor cells, according to its metastatic activity, can modulate T cell activity systemically. Moreover, and not less important, we show that cancer induced bone disease starts before metastatic colonization and is mediated by RANKL expressed in tumor specific T cells. We propose that this is the very first step on the establishment of the “vicious cycle” which will allow tumor growth.

We believe this work can open new avenues on the prognostic evaluation and treatment of women with breast cancer.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-01-02.

Group II metabotropic glutamate receptor activation by agonist LY379268 treatment increases the expression of brain derived neurotrophic factor in the mouse brain

A number of in vitro and in vivo studies using selective agonists have indicated a neuroprotective role for group-II metabotropic glutamate (mGlu2/3) receptors in various models of neuronal injury. Although an interplay among neurotrophic factors and mGlu2/3 receptors signalling system has been suggested as possible mechanism involved on neuroprotection, at present poor information are available concerning the in vivo regulation by mGlu2/3 receptors activation of specific neurotrophic factors. By using in situ hybridization and western blotting methods the aim of present study was to analyse the potential regulatory role of selective mGluR2/3 agonist LY379268 treatment on brain derived neurotrophic factor (BDNF) expression in the mouse brain. The treatment with LY379268 evidenced a significant upregulation of BDNF mRNA levels in the cerebral cortex and in the hippocampal formation with a peak at 3 h from treatment and its disappearance already at 6 h from treatment. An analysis of dose-effect curve revealed that LY379268 may significantly enhance BDNF mRNA expression already at dose of 0.250 mg/kg b.w. The upregulation of BDNF mRNA expression was followed by a significant increase of BDNF protein levels at 24 h from LY379268 treatment. These effects of LY379268 treatment on BDNF expression were restricted to neuronal cells and were blocked by the new selective mGlu2/3 receptor antagonist LY341495, suggesting a receptor specificity. Taken together these findings suggest that several previous observed neuroprotective and trophic actions of mGluR2/3 agonists treatment may be mediated, at least in the cerebral cortex and hippocampal formation, by upregulation of BDNF expression.

Risk factors for type 2 diabetes in women attending menopause clinics in Italy: a cross-sectional study

OBJECTIVE

To analyze risk factors for type 2 diabetes among women attending menopause clinics in Italy for counselling about the menopause.

SUBJECTS

Women attending a network of first-level outpatient menopause clinics in Italy for general counselling about menopause or treatment of menopausal symptoms.

METHODS

Cross-sectional study with no exclusion criteria. Type 2 diabetes was defined according to National Diabetes Data Groups Indications and the fasting blood glucose at an oral glucose tolerance test within the previous year.

RESULTS

Out of the 44 694 considered in this analysis, 808 had a diagnosis of diabetes type 2 (1.8%). In comparison with women aged < 50 years, the multivariate odds ratios (OR) of type 2 diabetes were 1.31 (95% confidence interval (CI), 0.99-1.74) for women aged 50-52 years, 1.66 (95% CI, 1.27-2.17) at 53-56 years and 2.84 (95% CI, 2.20-3.67) in women aged > or = 57 years. Type 2 diabetes was less frequently reported in more educated women (OR high school/university vs. primary school = 0.44 (95% CI, 0.36-0.55)). Being overweight was associated with an increased risk of type 2 diabetes. In comparison with women reporting a low level of physical activity, the multivariate OR of type 2 diabetes was 0.67 (95% CI, 0.54-0.84) for women reporting regular physical activity. In comparison with premenopausal women, the multivariate OR of type 2 diabetes was 1.38 (95% CI, 1.03-1.84) in women with natural menopause. This finding was present also after allowing for the potential confounding effect of age. The multivariate OR of diabetes for users of hormonal replacement therapy was 0.58 (95% CI, 0.46-0.73).

CONCLUSIONS

This large cross-sectional study suggests that postmenopausal women are at higher risk of type 2 diabetes after allowance for the effect of age. Other main determinants of risk of type 2 diabetes in women around menopause were low socioeconomic status and being overweight. Diabetes was found less frequently in those taking hormone replacement therapy.

Relationship of neutrophil phagocytosis and oxidative burst with the subgingival microbiota of generalized aggressive periodontitis

INTRODUCTION

Polymorphonuclear neutrophil (PMN) dysfunctions have been associated with severe forms of periodontitis. This study evaluated the correlation between PMN phagocytosis and oxidative burst with the subgingival microbiota of patients with generalized aggressive periodontitis (GAgP).

METHODS

Heparinized peripheral blood samples were obtained from 18 GAgP patients and 11 periodontally healthy (PH) subjects, and PMNs were isolated on a Ficoll-Hypaque gradient. For phagocytosis analysis, PMNs were incubated with fluorescein-labeled Staphylococcus aureus. The oxidative burst was evaluated by incubation of PMNs with dihydroethidium and activation by S. aureus. The assays were examined using flow cytometry. Subgingival biofilm samples were obtained from periodontal sites with and without periodontitis and 24 species were detected by checkerboard.

RESULTS

A significantly lower phagocytosis rate was observed for patients with GAgP compared with PH subjects over time (P < 0.05). No differences between groups were found for superoxide production. GAgP patients presented significantly higher prevalence and levels of Porphyromonas gingivalis, Tannerella forsythia, and Aggregatibacter actinomycetemcomitans serotype b than controls (P < 0.05). Significant negative correlations between T. forsythia and P. gingivalis and PMN functions were observed.

CONCLUSIONS

GAgP subjects presented diminished phagocytic activity of peripheral PMNs and high prevalence and levels of classical periodontal pathogens.

Pathogenic effector T cell enrichment overcomes regulatory T cell control and generates autoimmune gastritis

Regulatory T cells (Treg) deficiency leads to a severe, systemic, and lethal disease, as showed in immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome patients, and scurfy mouse. Postneonatal thymectomy autoimmune gastritis has also been attributed to the absence of Tregs. In this case however, disease is mild, organ-specific, and, more important, it is not an obligatory outcome. We addressed this paradox comparing T cell compartments in gastritis-susceptible and resistant animals. We found that neonatal thymectomy-induced gastritis is not caused by the absence of Tregs. Instead of this, it is the presence of gastritogenic T cell clones that determines susceptibility to disease. The expansion of such clones under lymphopenic conditions results in a reduced Treg:effector T cell ratio that is not enough to control gastritis development. Finally, the presence of gastritogenic clones is determined by the amount of gastric Ag expressed in the neonatal thymus, emphasizing the importance of effector repertoire variability, present even in genetically identical subjects, to organ-specific autoimmune disease susceptibility.

Study of membrane potential in T lymphocytes subpopulations using flow cytometry

Background

Ion channels are involved in the control of membrane potential (ψ) in a variety of cells. The maintenance of ψ in human T lymphocytes is essential for T-cell activation and was suggested to depend mostly on the voltage-gated Kv1.3 channel. Blockage of Kv1.3 inhibits cytokine production and lymphocyte proliferation in vitro and suppresses immune response in vivo. T lymphocytes are a heterogeneous cell population and the expression of Kv1.3 varies among cell subsets. Oxonol diBA-C4-(3) was used to determine ψ by flow cytometry. The presence of distinct T cell subsets was evaluated by immunophenotyping techniques and the contribution of Kv1.3 channels for the maintenance of ψ was investigated using selective blockers.

Results

The distribution of ψ in T lymphocytes varied among blood donors and did not always follow a unimodal pattern. T lymphocytes were divided into CD3⁺/CD45RO^- and CD3⁺/CD45RO⁺ subsets, whose peak channel values of ψ were -58 ± 3.6 mV and -37 ± 4.1 mV, respectively. MgTX (specific inhibitor of Kv1.3 channels) had no significant effect in the ψ of CD3⁺/CD45RO^- subsets but depolarized CD3⁺/CD45RO⁺ cells to -27 ± 5.1 mV.

Conclusion

Combination of optical methods for determination of ψ by flow cytometry with immuophenotyping techniques opens new possibilities for the study of ion channels in the biology of heterogeneous cell populations such as T lymphocyte subsets.

Cooperative Activation of TLR2 and Bradykinin B2 Receptor Is Required for Induction of Type 1 Immunity in a Mouse Model of Subcutaneous Infection by Trypanosoma cruzi

We have previously reported that exogenous bradykinin activates immature dendritic cells (DCs) via the bradykinin B(2) receptor (B(2)R), thereby stimulating adaptive immunity. In this study, we show that these premises are met in a model of s.c. infection by Trypanosoma cruzi, a protozoan that liberates kinins from kininogens through its major protease, cruzipain. Intensity of B(2)R-dependent paw edema evoked by trypomastigotes correlated with levels of IL-12 produced by CD11c(+) dendritic cells isolated from draining lymph nodes. The IL-12 response induced by endogenously released kinins was vigorously increased in infected mice pretreated with inhibitors of angiotensin converting enzyme (ACE), a kinin-degrading metallopeptidase. Furthermore, these innate stimulatory effects were linked to B(2)R-dependent up-regulation of IFN-gamma production by Ag-specific T cells. Strikingly, the trypomastigotes failed to up-regulate type 1 immunity in TLR2(-/-) mice, irrespective of ACE inhibitor treatment. Analysis of the dynamics of inflammation revealed that TLR2 triggering by glycosylphosphatidylinositol-anchored mucins induces plasma extravasation, thereby favoring peripheral accumulation of kininogens in sites of infection. Further downstream, the parasites generate high levels of innate kinin signals in peripheral tissues through the activity of cruzipain. The demonstration that the deficient type 1 immune responses of TLR2(-/-) mice are rescued upon s.c. injection of exogenous kininogens, along with trypomastigotes, supports the notion that generation of kinin "danger" signals is intensified through cooperative activation of TLR2 and B(2)R. In summary, we have described a s.c. infection model where type 1 immunity is vigorously up-regulated by bradykinin, an innate signal whose levels in peripheral tissues are controlled by an intricate interplay of TLR2, B(2)R, and ACE.

G-CSF-treated granulocytes inhibit acute graft-versus-host disease

It has been shown that in vivo and in vitro treatment with G-CSF induces the generation of low-density granulocytes (LDGs), which copurify with PBMCs and inhibit IFN-gamma production by human T cells. These results prompted us to postulate an immunomodulatory role for LDGs in acute graft-versus-host disease (aGVHD). Here it is shown that in the mouse experimental model, in vivo and in vitro G-CSF treatment generates LDGs capable of inhibiting 80% of T-cell IFN-gamma production. To assess the role of these LDGs in aGVHD, lethally irradiated (C57BL/6 x BALB/c) F1 hosts were reconstituted with T cell-depleted bone marrow cells plus nylon wool-purified spleen cells from G-CSF-treated (G-NWS) or -nontreated (NWS) C57BL/6 donors. Recipients of G-NWS had a 75% survival rate in contrast to a rate of 25% in the NWS recipients. The protective effect was completely abolished, and the mortality rate was 100% if donor-cell infusion was treated with anti-Gr1. Moreover, if LDGs were infused with NWS, full protection of aGVHD was observed, and no signs of disease were evidenced by mortality rate, weight loss, or histopathology of target organs. These results revealed the unexpected immunosuppressive capacity of G-CSF based on the generation of LDGs, leading to the possibility of using these cells as inhibitors of aGVHD.

Linking immunity and hematopoiesis by bone marrow T cell activity

Two different levels of control for bone marrow hematopoiesis are believed to exist. On the one hand, normal blood cell distribution is believed to be maintained in healthy subjects by an "innate" hematopoietic activity, i.e., a basal intrinsic bone marrow activity. On the other hand, an "adaptive" hematopoietic state develops in response to stress-induced stimulation. This adaptive hematopoiesis targets specific lineage amplification depending on the nature of the stimuli. Unexpectedly, recent data have shown that what we call "normal hematopoiesis" is a stress-induced state maintained by activated bone marrow CD4+ T cells. This T cell population includes a large number of recently stimulated cells in normal mice whose priming requires the presence of the cognate antigens. In the absence of CD4+ T cells or their cognate antigens, hematopoiesis is maintained at low levels. In this review, we summarize current knowledge on T cell biology, which could explain how CD4+ T cells can help hematopoiesis, how they are primed in mice that were not intentionally immunized, and what maintains them activated in the bone marrow.

Atrophy of mesenteric lymph nodes in experimental Chagas' disease: differential role of Fas/Fas-L and TNFRI/TNF pathways

It is currently accepted that experimental acute infection by Trypanosoma cruzi promotes changes in secondary lymphoid organs, with general T and B lymphocyte polyclonal activation. Here we show that mesenteric lymph nodes (MLN) of acutely infected mice show severe atrophy due to extensive lymphocyte apoptosis. Accordingly, clusters of apoptotic cells are detected in the initial phase of infection in MLN but not in subcutaneous nodes. Moreover, such atrophy is independent of the infection route, parasite load or the mouse strain used. Studies in Fas-L deficient (BALB gld/gld+/+) and in TNF type 1 receptor (p55-/-) knockout mice indicate that both molecules are involved in MLN atrophy: Fas-L participates in cell death of CD4+ as well as B lymphocytes, whereas the TNF type 1 receptor is important for the apoptosis of CD4+ and CD8+ T lymphocytes. In contrast, perforin does not play a role, as lymph nodes from perforin-deficient mice do not behave differently from the corresponding wild types. Our data support the concept that, even in a systemic infection, differential (even opposing) responses can be found in different lymph node chains.

[Staging role of micrometastatic sentinel lymph nodes in breast cancer]

AIM

Axillary dissection may be avoided in patients with breast cancer and negative sentinel lymph node (SL); not all metastatic SL patients show metastasis on the remaining axillary lymph nodes. The purpose of this study was to evaluate the possible presence of metastases in the remaining axillary lymphatic glands, the so called not-SL, in patients with SL either macro- or micrometastatic, and to try to locate a subgroup of patients in which metastases are present only in SL.

METHODS

A retrospective study was conducted in 91 patients who from March 2000 to June 2003 underwent a biopsy of SL and dissection of the axillary cavity (23 patients with micrometastatic SL and 68 with macrometastatic SL). A multivariate analysis evaluated the statistic association with not-SL metastases of almost 22 prognostic factors.

RESULTS

Of the 68 patients affected by macrometastatic SL, 32 (47%) showed metastases of the not-SL; of the 23 patients with micrometastatic SL, 7 (30%) showed metastases of the not-SL. In the last 2 years, among all those patients with micrometastatic SL, the probability of disease at the not-SL reached the null percentage. During year 2000, 3 (50%) patients out of 6 with micrometastatic SL showed metastases at the not-SL; during years 2002/2003 no patients out of 8 with micrometastatic SL showed metastases at the not-SL. A multivariate analysis showed only 2 factors significantly associated to the metastatic not-SL: age (cut off 60 years) OR 4.6, P 0.003 and histological examination of the SL OR 2.8, P 0.003.

CONCLUSIONS

The average frequency of disease of not-SL in patients with either micro- or macrometastatic SL is not so different than values observed in literature. The predictive disease value of the remaining axillary lymphatic glands of the micrometastatic SL reached the null percentage in the last 2 years, therefore at seems to depend on the operators experience in SL biopsy technique. Among patients with metastatic SL (micro and macro), it was not possible to detect a subgroup in which not-SL are not metastatic with reasonable certainty. Nevertheless, a multivariate analysis showed the histological factor of the SL, to be significantly associated to not-SL metastases, as well as to the age-factor.

Apoptotic mimicry: an altruistic behavior in host/Leishmania interplay

Apoptosis is the most common phenotype observed when cells die through programmed cell death. The morphologic and biochemical changes that characterize apoptotic cells depend on the activation of a diverse set of genes. Apoptosis is essential for multicellular organisms since their development and homeostasis are dependent on extensive cell renewal. In fact, there is strong evidence for the correlation between the emergence of multicellular organisms and apoptosis during evolution. On the other hand, no obvious advantages can be envisaged for unicellular organisms to carry the complex machinery required for programmed cell death. However, accumulating evidence shows that free-living and parasitic protozoa as well as yeasts display apoptotic markers. This phenomenon has been related to altruistic behavior, when a subpopulation of protozoa or yeasts dies by apoptosis, with clear benefits for the entire population. Recently, phosphatidylserine (PS) exposure and its recognition by a specific receptor (PSR) were implicated in the infectivity of amastigote forms of Leishmania, an obligatory vertebrate intramacrophagic parasite, showing for the first time that unicellular organisms use apoptotic features for the establishment and/or maintenance of infection. Here we focus on PS exposure in the outer leaflet of the plasma membrane--an early hallmark of apoptosis--and how it modulates the inflammatory activity of phagocytic cells. We also discuss the possible mechanisms by which PS exposure can define Leishmania survival inside host cells and the evolutionary implications of apoptosis at the unicellular level.

Normal hematopoiesis is maintained by activated bone marrow CD4+ T cells

CD4(+) T cells produce hematopoietic-related cytokines and are essential for hematopoiesis stimulation during infection and hematologic recovery after bone marrow transplantation. However, it remains unclear if T cells are necessary to maintain normal hematopoiesis. We report here that, in T-cell-deficient mice, terminal differentiation of myeloid progenitors is defective, resulting in very low levels of granulocytes in the periphery. Hematopoiesis is restored after thymus graft or reconstitution with CD4(+) T cells but not CD8(+) T cells. Bone marrow CD4(+) T cells have an activated phenotype and produce cytokines, apparently, in the absence of exogenous stimulation. Transgenic mice carrying T-cell receptor specific for an ovalbumin peptide presented in the context of a specific class II molecule (I-A(d)) (DO11.10 RAG(-/-)) show the same hematopoietic deficiency as athymic mice. Their bone marrow CD4(+) T cells are not activated, suggesting that hematopoiesis maintenance requires the presence of cognate antigen in order to activate bone marrow T-helper cells. In fact, priming of transgenic mice with ovalbumin restores normal hematopoiesis. The data show that the current concept of "normal hematopoiesis" does not reflect a basal bone marrow activity, but it is an antigen-induced state maintained by constant activation of bone marrow CD4(+) T cells.

T-lymphocyte function from peripheral blood stem-cell donors is inhibited by activated granulocytes

BACKGROUND

PBSC transplant provides 10 times more T cells than BMT However, the incidence and severity of acute GvHD is similar among recipients of both types of transplants. Studies in mouse models suggest that the similar clinical outcome in BMT and PBSCT is due to differences in the lymphokine profiles.

METHODS

PBMC, PBMC from G-CSF mobilized donors (G-PBMC)and BM mononuclear cells (BM-MC) were analyzed by flow cytometry and ELISA to detect gamma-IFN and IL-4 production. Hematoxylin and eosin staining was used to identify morphology and annexin/propidium-iodide was used for apoptosis assays.

RESULTS

We show decreased production of gamma-interferon (85%) and IL-4 (60%) in G-PBMC when compared with either PBMC or BM-MCT cells on ex vivo assays. Surprisingly, 85% of fresh G-PBMC is composed of low-density granulocytes (LDG), which undergo apoptosis after 48 h in culture. At this same time, gamma-IFN production from G-PBMC T cell was reverted. In vitro, G-CSF converts granulocytes into LDGs, able to inhibit T-cell function by H2O2 production, and not through immune-deviation towards a Th2-type phenotype.

DISCUSSION

We show that the estimated numbers of Th1 and Th2 cells infused in BMT and PBSCT do not differ significantly. These findings are discussed with reference to the relatively low incidence of acute GvHD in PBSCT shown in the literature. We suggest that these results might depend on the high number of granulocytes and progenitors infused. The potential use of granulocytes as immunosupressive short-term therapy is now being investigated by our group using a mouse experimental model.

Bone marrow stroma inhibits proliferation and apoptosis in leukemic cells through gap junction-mediated cell communication

Normal and leukemic blood cell progenitors depend upon the bone marrow (BM) stroma with which they communicate through soluble and membrane-anchored mediators, adhesive interactions and gap junctions (GJ). Regarding hematopoiesis, it is believed that it can be influenced by connexin expression, but the exact role of GJ in cell death and proliferation is not clear. Using flow cytometry, we monitored the division rate of leukemic cell lines, communicating and not communicating with stromal cell line through GJ. We found that GJ-coupled cells (i) did not proliferate; (ii) were kept in G0; and (iii) were protected from drug-induced apoptosis when compared to either total or uncoupled cell population. We conclude that GJ coupling between stroma and leukemic lymphoblasts prevents proliferation, keeping cells in a quiescent state, thus increasing their resistance to antimitotic drugs. Since GJ are particularly abundant in the sub-endosteal environment, which harbors blood stem cells, we also asked which cells within the normal human BM communicate with the stroma. Using a primary BM stroma cell culture, our results show that 80% of CD34+ progenitors communicate through GJ. We propose that blood cell progenitors might be retained in the low-cycling state by GJ-mediated communication with the hematopoietic stroma.

Trypanosoma cruzi infection modulates intrathymic contents of extracellular matrix ligands and receptors and alters thymocyte migration

Several T cell abnormalities have been described in the course of acute Trypanosoma cruzi infection in mice, including severe effects on the thymus. In the present study, looking at the expression of extracellular matrix ligands in the thymus, we observed that deposits of fibronectin and laminin increased progressively during the course of infection, reaching a maximum at the peak of parasitemia and thymic atrophy. Concomitantly, membrane expression of fibronectin and laminin receptors (VLA-4, VLA-5 and VLA-6) was also enhanced on thymocyte subsets of infected mice. These results correlated with changes in intrathymic thymocyte migration ability during the acute phase of infection, when a higher fibronectin-dependent transmigratory activity of CD4(+)CD8(+) thymocytes was observed. Strikingly, we detected higher frequency of immature and high VLA-expressing CD4(+)CD8(+) T cells in the peripheral lymphoid organs of infected mice at the peak of parasitemia. These cells seemed to be thymus dependent, since significantly lower amounts of them were found in thymectomized mice, and some of them carry "prohibited" Vbeta segments of the TCR. Our data suggest an imbalance in the intrathymic cell trafficking following acute T. cruzi infection, likely due to dysregulated extracellular matrix-dependent interactions.

Soluble factors released by Toxoplasma gondii-infected astrocytes down-modulate nitric oxide production by gamma interferon-activated microglia and prevent neuronal degeneration

The maintenance of a benign chronic Toxoplasma gondii infection is mainly dependent on the persistent presence of gamma interferon (IFN-gamma) in the central nervous system (CNS). However, IFN-gamma-activated microglia are paradoxically involved in parasitism control and in tissue damage during a broad range of CNS pathologies. In this way, nitric oxide (NO), the main toxic metabolite produced by IFN-gamma-activated microglia, may cause neuronal injury during T. gondii infection. Despite the potential NO toxicity, neurodegeneration is not a common finding during chronic T. gondii infection. In this work, we describe a significant down-modulation of NO production by IFN-gamma-activated microglia in the presence of conditioned medium of T. gondii-infected astrocytes (CMi). The inhibition of NO production was paralleled with recovery of neurite outgrowth when neurons were cocultured with IFN-gamma-activated microglia in the presence of CMi. Moreover, the modulation of NO secretion and the neuroprotective effect were shown to be dependent on prostaglandin E(2) (PGE(2)) production by T. gondii-infected astrocytes and autocrine secretion of interleukin-10 (IL-10) by microglia. These events were partially eliminated when infected astrocytes were treated with aspirin and cocultures were treated with anti-IL-10 neutralizing antibodies and RP-8-Br cyclic AMP (cAMP), a protein kinase A inhibitor. Further, the modulatory effects of CMi were mimicked by the presence of exogenous PGE(2) and by forskolin, an adenylate cyclase activator. Altogether, these data point to a T. gondii-triggered regulatory mechanism involving PGE(2) secretion by astrocytes and cAMP-dependent IL-10 secretion by microglia. This may reduce host tissue inflammation, thus avoiding neuron damage during an established Th1 protective immune response.

Isolation and characterization of hemopoietic cells from lungs of allergic mice

We developed a procedure for the isolation of hemopoietic cells from murine lung. Ovalbumin sensitization and challenge increased the numbers of functionally intact hemopoietic progenitors recovered from digested lung fragments by 80-fold to 120-fold, relative to naive controls. Eosinophil precursors, which are absent in the naive mouse lung, accumulated in the lungs of sensitized/challenged mice. Progenitors in allergic BALB/c mice were recoverable from lung parenchyma, not blood or airways, and were exclusively CD34+. Precursors isolated from allergic lung, unlike those from bone marrow, were inhibited by dexamethasone and were stimulated by prostaglandin D(2). This directly demonstrates that sensitized/challenged lungs accumulate hemopoietic progenitors and precursors, distinct from those in bone marrow.

Serum levels of cobalt and chromium in a complex modular total hip arthroplasty system

There is concern that modularity in a total hip arthroplasty system increases serum cobalt and chromium ion levels. This study measures the serum cobalt and chromium levels in patients with an Oxford Universal Hip (Corin, Cirencester, United Kingdom), which has a modular sliding mechanism; patients with a similarly manufactured hip with no sliding mechanism; and a control group. Loosening was excluded clinically and radiologically. Arthroplasty patients had statistically higher levels of serum cobalt and chromium than controls, but there was no significant difference in levels between the implanted groups.

Apoptotic mimicry by an obligate intracellular parasite downregulates macrophage microbicidal activity

Programmed cell death by apoptosis of unnecessary or potentially harmful cells is clearly beneficial to multicellular organisms. Proper functioning of such a program demands that the removal of dying cells proceed without an inflammatory reaction. Phosphatidylserine (PS) is one of the ligands displayed by apoptotic cells that participates in their noninflammatory removal when recognized by neighboring phagocytes. PS ligation induces the release of transforming growth factor-beta (TGF-beta), an antiinflammatory cytokine that mediates the suppression of macrophage-mediated inflammation. In Hydra vulgaris, an organism that stands at the base of metazoan evolution, the selective advantage provided by apoptosis lies in the fact that Hydra can survive recycling apoptotic cells by phagocytosis. In unicellular organisms, it has been proposed that altruistic death benefits clonal populations of yeasts and trypanosomatids. Now we show that advantageous features of the apoptotic process can operate without death as the necessary outcome. Leishmania spp are able to evade the killing activity of phagocytes and establish themselves as obligate intracellular parasites. Amastigotes, responsible for disease propagation, similar to apoptotic cells, inhibit macrophage activity by exposing PS. Exposed PS participates in amastigote internalization. Recognition of this moiety by macrophages induces TGF-beta secretion and IL-10 synthesis, inhibits NO production, and increases susceptibility to intracellular leishmanial growth.

Does arthritis progress in the retained compartments after ‘Oxford’ medial unicompartmental arthroplasty?

We determined the outcome of 56 ‘Oxford’ unicompartmental replacements performed for anteromedial osteoarthritis of the knee between 1982 and 1987. Of these, 24 were in patients who had died without revision, one was lost to follow-up and two had been revised. Of the remaining 29 knees, 26 were examined clinically and radiologically, two were only examined clinically and one patient was contacted by telephone. The mean age of the patients was 80.3 years.

At a mean follow-up of 11.4 years (10 to 14) the measurements of the knee score, range of movement and degree of deformity were not significantly different from those made one to two years after operation, except that the range of flexion had improved. Comparison of fluoroscopically-controlled radiographs at a similar interval of time showed no change in the appearance of the lateral compartments. The retained articular cartilage continued to function for ten or more years which suggests that anteromedial osteoarthritis may be considered as a focal disorder of the knee. This justifies continued efforts to develop methods of treatment which preserve intact joint structures.

Does arthritis progress in the retained compartments after 'Oxford' medial unicompartmental arthroplasty? A clinical and radiological study with a minimum ten-year follow-up

We determined the outcome of 56 'Oxford' unicompartmental replacements performed for anteromedial osteoarthritis of the knee between 1982 and 1987. Of these, 24 were in patients who had died without revision, one was lost to follow-up and two had been revised. Of the remaining 29 knees, 26 were examined clinically and radiologically, two were only examined clinically and one patient was contacted by telephone. The mean age of the patients was 80.3 years. At a mean follow-up of 11.4 years (10 to 14) the measurements of the knee score, range of movement and degree of deformity were not significantly different from those made one to two years after operation, except that the range of flexion had improved. Comparison of fluoroscopically-controlled radiographs at a similar interval of time showed no change in the appearance of the lateral compartments. The retained articular cartilage continued to function for ten or more years which suggests that anteromedial osteoarthritis may be considered as a focal disorder of the knee. This justifies continued efforts to develop methods of treatment which preserve intact joint structures.

Extramedullar B lymphopoiesis in liver schistosomal granulomas: presence of the early stages and inhibition of the full B cell differentiation

Inflammatory granulomatous reactions in liver elicited by schistosomal infection have been shown to function as active extramedullar myelopoietic sites, producing potentially all the myeloid lineages. We have now addressed the question of the extramedullar B lymphopoiesis in these sites. We have shown the presence of early B cell precursors (pro-B cells) in the granulomas by immunophenotyping. Their total number in the liver was equivalent to the pro-B cells in the bone marrow of one femur. In agreement with their phenotype, the RT-PCR analysis showed that these cells expressed RAG-1 and lambda5 genes. However, the conversion of the pro-B to pre-B cells was not observed and no clonogenic B cell precursors could be detected in semi-solid cultures stimulated by IL-7. The granulomatous stroma was shown to produce IL-7 and express c-kit, and was able to sustain the full B lymphopoiesis in vitro. Conversely, the granuloma supernatant was shown to inhibit actively the development of B lymphocytes. We conclude that the granuloma environment elicits homing and proliferation of totipotent hematopoietic precursors, and that it is permissive for early commitment to the B cell lineage, but the full extramedullar production of B cell is abrogated by soluble factors produced inside the granulomas.

Involvement of laminin and its receptor in abrogation of heart graft rejection by autoreactive T cells from Trypanosoma cruzi-infected mice

Extracellular matrix ligands and receptors have been identified as determining in vivo lymphocyte positioning and activation, including effector functions in alloreactive responses. Herein we evaluated the involvement of laminin and its receptor, the very late antigen 6 (VLA-6) integrin, in CD4+ T cell-dependent autoreactivity, using a transplantation model for the autoimmune myocarditis occurring in mice chronically infected with Trypanosoma cruzi. Previous work showed that syngeneic mouse hearts grafted in the ears of chronic chagasic recipients were rejected through a CD4+ T cell-dependent mechanism. Rejection also occurred when cells from chagasic animals were transferred adjacent to hearts transplanted into naive recipients. Here, we observed the formation of a thick laminin network during rejection, with donor-derived CD4+ T cells concentrated in the laminin-rich areas. Most importantly, anti-laminin as well as anti-laminin receptor Ab inhibited the rejection of syngeneic hearts by T cells from chagasic animals. Our results suggest that interaction of the VLA-6 molecule with laminin is involved in triggering the antimyocardial autoreactive process by driving the influx of CD4+ T cells to the heart. They also support the concept that an Ag-specific T cell response, even an autoreactive one, can be modulated by in vivo interactions involving extracellular matrix ligands and receptors. In this regard, our study represents, to our knowledge, the first in vivo evidence for laminin-mediated T cell echotaxis, with simultaneous experimental demonstration of ligand and receptor involvement. Lastly, our findings indicate that treatment with anti-VLA-6 Abs can be effective in suppressing autoimmune disease activity.

Involvement of laminin and its receptor in abrogation of heart graft rejection by autoreactive T cells from Trypanosoma cruzi-infected mice

Extracellular matrix ligands and receptors have been identified as determining in vivo lymphocyte positioning and activation, including effector functions in alloreactive responses. Herein we evaluated the involvement of laminin and its receptor, the very late antigen 6 (VLA-6) integrin, in CD4+ T cell-dependent autoreactivity, using a transplantation model for the autoimmune myocarditis occurring in mice chronically infected with Trypanosoma cruzi. Previous work showed that syngeneic mouse hearts grafted in the ears of chronic chagasic recipients were rejected through a CD4+ T cell-dependent mechanism. Rejection also occurred when cells from chagasic animals were transferred adjacent to hearts transplanted into naive recipients. Here, we observed the formation of a thick laminin network during rejection, with donor-derived CD4+ T cells concentrated in the laminin-rich areas. Most importantly, anti-laminin as well as anti-laminin receptor Ab inhibited the rejection of syngeneic hearts by T cells from chagasic animals. Our results suggest that interaction of the VLA-6 molecule with laminin is involved in triggering the antimyocardial autoreactive process by driving the influx of CD4+ T cells to the heart. They also support the concept that an Ag-specific T cell response, even an autoreactive one, can be modulated by in vivo interactions involving extracellular matrix ligands and receptors. In this regard, our study represents, to our knowledge, the first in vivo evidence for laminin-mediated T cell echotaxis, with simultaneous experimental demonstration of ligand and receptor involvement. Lastly, our findings indicate that treatment with anti-VLA-6 Abs can be effective in suppressing autoimmune disease activity.