Cell-directed-assembly: directing the formation of nano/bio interfaces and architectures with living cells

BACKGROUND

The desire to immobilize, encapsulate, or entrap viable cells for use in a variety of applications has been explored for decades. Traditionally, the approach is to immobilize cells to utilize a specific functionality of the cell in the system.

SCOPE OF REVIEW

This review describes our recent discovery that living cells can organize extended nanostructures and nano-objects to create a highly biocompatible nano//bio interface [1].

MAJOR CONCLUSIONS

We find that short chain phospholipids direct the formation of thin film silica mesophases during evaporation-induced self-assembly (EISA) [2], and that the introduction of cells alter the self-assembly pathway. Cells organize an ordered lipid-membrane that forms a coherent interface with the silica mesophase that is unique in that it withstands drying-yet it maintains accessibility to molecules introduced into the 3D silica host. Cell viability is preserved in the absence of buffer, making these constructs useful as standalone cell-based sensors. In response to hyperosmotic stress, the cells release water, creating a pH gradient which is maintained within the nanostructured host and serves to localize lipids, proteins, plasmids, lipidized nanocrystals, and other components at the cellular surface. This active organization of the bio/nano interface can be accomplished during ink-jet printing or selective wetting-processes allowing patterning of cellular arrays-and even spatially-defined genetic modification.

GENERAL SIGNIFICANCE

Recent advances in the understanding of nanotechnology and cell biology encourage the pursuit of more complex endeavors where the dynamic interactions of the cell and host material act symbiotically to obtain new, useful functions. This article is part of a Special Issue entitled Nanotechnologies - Emerging Applications in Biomedicine.

Cell-directed integration into three-dimensional lipid-silica nanostructured matrices

We report a unique approach in which living cells direct their integration into 3D solid-state nanostructures. Yeast cells deposited on a weakly condensed lipid/silica thin film mesophase actively reconstruct the surface to create a fully 3D bio/nano interface, composed of localized lipid bilayers enveloped by a lipid/silica mesophase, through a self-catalyzed silica condensation process. Remarkably, this integration process selects exclusively for living cells over the corresponding apoptotic cells (those undergoing programmed cell death), via the development of a pH gradient, which catalyzes silica deposition and the formation of a coherent interface between the cell and surrounding silica matrix. Added long-chain lipids or auxiliary nanocomponents are localized within the pH gradient, allowing the development of complex active and accessible bio/nano interfaces not achievable by other synthetic methods. Overall, this approach provides the first demonstration of active cell-directed integration into a nominally solid-state three-dimensional architecture. It promises a new means to integrate "bio" with "nano" into platforms useful to study and manipulate cellular behavior at the individual cell level and to interface living organisms with electronics, photonics, and fluidics.

A multifunctional thin film Au electrode surface formed by consecutive electrochemical reduction of aryl diazonium salts

A multifunctional thin film surface capable of immobilizing two diverse molecules on a single gold electrode was prepared by consecutive electrodeposition of nitrophenyl and phenylboronic acid pinacol ester (PBA-PE) diazonium salts. Activation of the stacked film toward binding platinum nanoparticles (PtNPs) and yeast cells occurred via chemical deprotection of the pinacol ester followed by electroreduction of nitro to amino groups. FTIR spectral analysis was used to study and verify film composition at each stage of preparation. The affect of electrodeposition protocol over the thickness of the nitrophenyl and PBA-PE layers was explored and had a profound impact on the film properties. Thicker nitrophenyl films led to diminished PBA-PE diazonium reduction currents during assembly and decreased phenylboronic acid (PBA) layer thickness while allowing for higher PtNP loading and catalytic currents from PtNP-mediated peroxide reduction. Multilayer PBA films could be formed over the nitrophenyl film; however, only submonlayer PBA films permitted access to the underlying layer. The sequence of functional group activation toward binding was also shown to be significant, as perchlorate used to remove pinacol ester also converted aminophenyl groups accessible to the solution to nitrophenyl groups, preventing electrostatic PtNP binding. Finally, SEM images show PtNPs immobilized in close proximity (nanometers) to captured yeast cells on the PBA-aminophenyl-Au film. Such multibinding functionality films that maintain conductivity for subsequent electrochemical measurements hold promise for the development of electrochemical and/or optical platforms for fundamental cell studies, genomic and proteomic analysis, and biosensing.

Relationship between arterial, mixed venous, and internal jugular carboxyhemoglobin concentrations at low, medium, and high concentrations in a piglet model of carbon monoxide toxicity

OBJECTIVE

This study tested the hypothesis that mixed venous carboxyhemoglobin concentrations (V-COHb) and internal jugular carboxyhemoglobin concentrations (I-COHb) accurately predict arterial carboxyhemoglobin concentrations (A-COHb). In addition, this study tested the hypothesis that there is a high correlation at low (COHb, 0% to 10%), moderate (COHb, >10% to 40%), and high (COHb, >40%) concentrations between V-COHb, I-COHb, and A-COHb.

DESIGN

The study was a prospective comparison of A-COHb, V-COHb, and I-COHb concentrations in piglets exposed to increasing concentrations of carbon monoxide over 6 hrs to achieve a concentration of > or =60% COHb. Carboxyhemoglobin measurements were evaluated by analysis of variance and correlation analysis. Agreement between V-COHb and A-COHb concentrations was examined by using a plot of arteriovenous differences against the mean of the two measurements.

INTERVENTION

We simultaneously sampled arterial, mixed venous, and internal jugular blood every 30 mins over the 6-hr study period.

RESULTS

Two hundred fifty arterial and mixed venous COHb concentrations were obtained, and 214 internal jugular COHb concentrations were obtained. One hundred additional arterial, mixed venous, internal jugular, and peripheral COHb concentrations were obtained. Correlation between samples at each concentration revealed r2 > = .94.

CONCLUSION

Venous COHb concentrations predict arterial COHb concentrations with a high degree of accuracy and are correlated at low, moderate, and high concentrations of carbon monoxide exposure. Arterial or venous samples can be used to accurately measure COHb concentrations.

Early block in maturation is associated with thymic involution in mammary tumor-bearing mice

We previously reported that mice implanted with mammary tumors show a progressive thymic involution that parallels the growth of the tumor. The involution is associated with a severe depletion of CD4+8+ thymocytes. We have investigated three possible mechanisms leading to this thymic atrophy: 1) increased apoptosis, 2) decreased proliferation, and 3) disruption of normal thymic maturation. The levels of thymic apoptosis were determined by propidium iodide and annexin V staining. A statistically significant, but minor, increase in thymic apoptosis in tumor-bearing mice was detected with propidium iodide and annexin V staining. The levels of proliferation were assessed by in vivo labeling with 5'-bromo-2'-deoxyuridine (BrdU). The percentages of total thymocytes labeled 1 day following BrdU injection were similar in control and tumor-bearing mice. Moreover, the percentages of CD4-8- thymocytes that incorporated BrdU during a short term pulse (5 h) of BrdU were similar. Lastly, thymic maturation was evaluated by examining CD44 and CD25 expression among CD4-8- thymocytes. The percentage of CD44+ cells increased, while the percentage of CD25+ cells decreased among CD4-8- thymocytes from tumor-bearing vs control animals. Together, these findings suggest that the thymic hypocellularity seen in mammary tumor bearers is not due to a decreased level of proliferation, but, rather, to an arrest at an early stage of thymic differentiation along with a moderate increase in apoptosis.

Elevated GM-CSF levels in tumor bearing mice upregulate IL-6 production by B cells via a mechanism independent of TNF-alpha

During mammary tumorigenesis a profound dysregulation of cytokine production by various lymphoreticular cells has been documented. B lymphocytes from tumor bearers have an increased production of tumor necrosis factor alpha (TNF-alpha). We now report that these lymphocytes have elevated levels of interleukin 6 (IL-6) at the transcriptional and translational levels, that are reflected systemically. The mammary tumor used in our study constitutively produces several factors including granulocyte-macrophage colony stimulating factor (GM-CSF), prostaglandin E2 (PGE2) and phosphatidyl serine (PS), which directly or indirectly can affect the cells of the immune system. in vitro addition of GM-CSF resulted in a dramatic increase in IL-6 levels from B cells from normal mice. This effect does not appear to be due to elevated levels of TNF-alpha, known to upregulate IL-6. Rather, GM-CSF activates IL-6 production independently of TNF-alpha as demonstrated by neutralization studies using anti-TNF-alpha antibodies. Furthermore, the effect exerted by GM-CSF on IL-6 production by B lymphocytes appears to be direct since pretreatment of cultures with anti-GM-CSF completely abrogated the elevated production of IL-6. The elevated levels of IL-6 and TNF-alpha in tumor bearers may contribute to the cachectic state observed in tumor bearing mice.

Abnormal binding pattern and composition of the NF-kappaB complex components are involved in increased TNF-alpha production by tumor bearer B cells

B lymphocytes from mammary tumor bearers are cytotoxic against tumor targets and produce TNF-alpha. A greater stability of RNA and a decreased rate of RNA degradation was observed in B cells of tumor bearers compared to those of normal mice. The TNF-alpha promoter contains regions that bind NF-kappaB, which regulate the rate of transcription. Supershift assays for the NF-kappaB region showed that there are p50-p65 heterodimers and p50 homodimers in the nuclear extracts of the two types of B cells, while those from tumor bearers lack the c-Rel component that is present in normal B cells. These results indicate that abnormalities in binding and composition of the NF-kappaB complexes may be involved in the increased TNF-alpha production by B cells of tumor bearers.

CD4+, but not CD8+, T cells from mammary tumor-bearing mice have a down-regulated production of IFN-gamma: role of phosphatidyl serine

IFN-gamma production is dramatically reduced in T cells from mice bearing large mammary tumors. This inhibition of IFN-gamma gene expression occurs mostly in CD4+ T cells, as determined by ELISA and reverse transcriptase-PCR. The effects of known mammary tumor factors in normal T cells and its subsets were evaluated. Pretreatment with granulocyte-macrophage CSF resulted in increased IFN-gamma levels by T cells, while PGE2 pretreatment equally decreased the levels of this cytokine in CD4+ and CD8+ T cells from normal mice. Interestingly, phosphatidyl serine (PS) down-regulated the IFN-gamma production of CD4+, but not that of CD8+, T cells. Methylation analysis indicated that the CpG dinucleotide in SnaBI site of the IFN-gamma 5' promoter flank region was hypermethylated in CD4+, but not in CD8+, T cells of large tumor bearers and of normal mice pretreated with PS. Electrophoresis mobility shift assay using an oligonucleotide probe corresponding to the IFN-gamma promoter core region sequence showed a greatly reduced binding of a 90-kDa nuclear protein in CD4+ T cells from tumor bearers and in those from PS-pretreated normal mice. Since IL-2 production is not affected in either CD4+ or CD8+ T cells from tumor bearers, these studies indicate that IFN-gamma production can be regulated independently from that of other type 1 cytokines in vivo. Our data further suggest that PS is involved in IFN-gamma gene down-regulation during mammary tumorigenesis and contributes to the generalized immunosuppression associated with tumor growth.

Altered binding of the NF-GMa transcription factor is involved in the upregulated production of TNF-alpha by macrophages of mammary tumor bearing mice

Macrophages from D1-DMBA-3 mammary tumor bearing mice have profound alterations in various functions, i.e. diminished antigen presentation, decreased cytolytic activity and depressed synthesis of IL-12. In contrast, these cells display a significant enhancement in the levels of TNF-alpha, which may be involved in the cachexia observed in animals bearing large mammary tumors. The molecular mechanisms involved in the upregulation of TNF-alpha in macrophages from tumor bearers were investigated. The levels of TNF-alpha RNA were increased in macrophages from tumor bearers, but, this was not due to an increase in the RNA half-life. An analysis of the binding of transcription factors relevant to the TNF-alpha gene regulatory region by electrophoretic mobility shift assays (EMSA) revealed no differences in the binding of any NF-kB complex component between macrophages from normal and tumor bearing mice. Likewise, there were no changes in the binding patterns of SP-1 and NF-Y. In contrast, the binding of the transcription factor, NF-GMa, was altered in macrophages from tumor bearers. Our results and those reported in other models of disease suggest that the excessive production of cytokines in pathological conditions, could be the result of alterations of the production and/or binding of transcription factors.

Phosphatidyl serine is involved in the reduced rate of transcription of the inducible nitric oxide synthase gene in macrophages from tumor-bearing mice

Upon stimulation with LPS, peritoneal-elicited macrophages (PEM) from mammary tumor-bearing mice display a diminished ability to produce nitric oxide (NO) and lyse tumor targets. In contrast, when these cells are stimulated with LPS in combination with IFN-gamma, they perform these functions at normal levels. Kinetic studies revealed that these defects became more pronounced with tumor progression and were accompanied by similar changes in inducible nitric oxide synthase (iNOS) mRNA levels. Since this tumor is known to produce PGE2, granulocyte-macrophage CSF (GM-CSF), and phosphatidyl serine, we evaluated the effects of these products on NO production and cytolytic activity. Pretreatment of normal PEM with PGE2 or recombinant GM-CSF had negligible effects on NO production and cytolytic capacity. In contrast, phosphatidyl serine caused a concentration-dependent inhibition of these functions in response to LPS, which could be partially overcome by the addition of IFN-gamma. Moreover, iNOS mRNA levels paralleled these changes and were analogous to the alterations observed in the tumor-bearers' PEM. iNOS mRNA stability was not reduced in these cells; however, the rate of transcription was diminished relative to normal levels, suggesting that the defects causing these alterations are occurring at or before the level of iNOS transcription. These data implicate tumor-derived phosphatidyl serine in the alterations observed in tumor-bearers' macrophages and suggest that reduced iNOS transcription is responsible for the diminished capacity of these macrophages to produce NO and lyse tumor targets.

Phosphatidyl serine is involved in the reduced rate of transcription of the inducible nitric oxide synthase gene in macrophages from tumor-bearing mice

Upon stimulation with LPS, peritoneal-elicited macrophages (PEM) from mammary tumor-bearing mice display a diminished ability to produce nitric oxide (NO) and lyse tumor targets. In contrast, when these cells are stimulated with LPS in combination with IFN-gamma, they perform these functions at normal levels. Kinetic studies revealed that these defects became more pronounced with tumor progression and were accompanied by similar changes in inducible nitric oxide synthase (iNOS) mRNA levels. Since this tumor is known to produce PGE2, granulocyte-macrophage CSF (GM-CSF), and phosphatidyl serine, we evaluated the effects of these products on NO production and cytolytic activity. Pretreatment of normal PEM with PGE2 or recombinant GM-CSF had negligible effects on NO production and cytolytic capacity. In contrast, phosphatidyl serine caused a concentration-dependent inhibition of these functions in response to LPS, which could be partially overcome by the addition of IFN-gamma. Moreover, iNOS mRNA levels paralleled these changes and were analogous to the alterations observed in the tumor-bearers' PEM. iNOS mRNA stability was not reduced in these cells; however, the rate of transcription was diminished relative to normal levels, suggesting that the defects causing these alterations are occurring at or before the level of iNOS transcription. These data implicate tumor-derived phosphatidyl serine in the alterations observed in tumor-bearers' macrophages and suggest that reduced iNOS transcription is responsible for the diminished capacity of these macrophages to produce NO and lyse tumor targets.

Down-regulation of IL-12, not a shift from a T helper-1 to a T helper-2 phenotype, is responsible for impaired IFN-gamma production in mammary tumor-bearing mice

Altered cytokine production has been implicated in the down-regulation of cell-mediated immunity in mice bearing large mammary tumors. In several diseases, an imbalance between helper T lymphocytes Th1 and Th2 and their cytokines has been suggested as a contributing factor. In this study, although IFN-gamma from splenic T cells of D1-DMBA-3 mammary tumor-bearing mice was greatly diminished, other cytokine levels remained unchanged, indicating no clear shift between the Th1, Th2, or Th3 phenotypes. The IFN-gamma levels can be restored in vitro by addition of rIL-12 to cultured splenocytes from tumor bearers. Furthermore, IL-12 production is greatly down-regulated in macrophages from tumor-bearing mice as detected by ELISA, and this correlates with diminished expression of IL-12 p40 chain RNA. The mammary tumor used in our studies produces several factors, including granulocyte macrophage-CSF, PGE2, and phosphatidyl serine, that can affect the immune system. Addition of these tumor-derived factors in vitro to macrophages from normal mice resulted in decreased levels of IL-12 protein in cultures treated with PGE2 or phosphatidyl serine. These results indicate that the down-regulation of T cell-produced IFN-gamma in this tumor model is the result of decreased IL-12 production caused by tumor-derived factors and not a shift from the Th1 to the Th2 phenotype.

Down-regulation of IL-12, not a shift from a T helper-1 to a T helper-2 phenotype, is responsible for impaired IFN-gamma production in mammary tumor-bearing mice

Altered cytokine production has been implicated in the down-regulation of cell-mediated immunity in mice bearing large mammary tumors. In several diseases, an imbalance between helper T lymphocytes Th1 and Th2 and their cytokines has been suggested as a contributing factor. In this study, although IFN-gamma from splenic T cells of D1-DMBA-3 mammary tumor-bearing mice was greatly diminished, other cytokine levels remained unchanged, indicating no clear shift between the Th1, Th2, or Th3 phenotypes. The IFN-gamma levels can be restored in vitro by addition of rIL-12 to cultured splenocytes from tumor bearers. Furthermore, IL-12 production is greatly down-regulated in macrophages from tumor-bearing mice as detected by ELISA, and this correlates with diminished expression of IL-12 p40 chain RNA. The mammary tumor used in our studies produces several factors, including granulocyte macrophage-CSF, PGE2, and phosphatidyl serine, that can affect the immune system. Addition of these tumor-derived factors in vitro to macrophages from normal mice resulted in decreased levels of IL-12 protein in cultures treated with PGE2 or phosphatidyl serine. These results indicate that the down-regulation of T cell-produced IFN-gamma in this tumor model is the result of decreased IL-12 production caused by tumor-derived factors and not a shift from the Th1 to the Th2 phenotype.

Cytokine production by lymphoreticular cells from mammary tumor bearing mice: the role of tumor-derived factors

Mammary tumor development has multiple effects on the T cell, B cell and macrophage compartments of the hosts as evidenced by the alterations in their phenotype and functions. Cytokines are known to modulate the immune system, thus a study of the production of these factors has great relevance to tumor immunity. Here we present evidence that tumor progression causes a profound dysregulation of the cytokine production by various lymphoreticular cells. Furthermore, the tumors themselves are capable of secreting factors that can directly or indirectly affect the cells of the immune system, thereby resulting in the immunosuppressive and other deleterious effects that favor the progress of the neoplastic disease.

The altered tumoricidal capacity of macrophages isolated from tumor-bearing mice is related to reduce expression of the inducible nitric oxide synthase gene

Nitric oxide (NO) is a major effector molecule in the destruction of tumor cells by activated macrophages. However, in many cases, developing neoplasms appear to be capable of impairing steps in the complex process leading to NO production as a means of avoiding immune destruction. After activation with lipopolysaccharide (LPS), peritoneal-elicited macrophages (PEM) from mice bearing mammary tumors display alterations in their ability to lyse tumor cells due to reduced production of NO. In contrast, when these same cells are stimulated with LPS in combination with interferon gamma (IFN-gamma), they are able to produce NO and lyse targets at normal levels. Since tumor-associated macrophages are intimately associated with the cells of the developing tumor, their ability to produce NO and lyse tumor targets is likely to be more relevant to controlling tumor growth. This population of macrophages exhibited a more profound inability to produce NO and lyse targets and, unlike the PEM, was not able to upregulate these functions even when treated with combinations of LPS and IFN-gamma. Northern and Western blots revealed that inducible nitric oxide synthase (iNOS) mRNA and protein levels correlated directly with the ability of each macrophage population to produce NO, and the levels of these macromolecules were altered sufficiently in tumor bearers' macrophages to account for the diminished NO production described. These results indicate that a spatial gradient of suppression of macrophage cytolytic activity and iNOS expression exists in mammary tumor-bearing mice, whereby macrophages from within the tumor exhibit a more pronounced suppression than the more distally located PEM. This suppression may be due to proximity of the macrophages to the developing tumor, macrophage maturational state, or both.

Epidermal Langerhans cells from mice bearing a granulocyte macrophage-colony stimulating factor-producing mammary tumor display impaired accessory functions

A progressive depression of delayed type hypersensitivity reactions occurs during development of mammary tumors in BALB/c mice. This tumor constitutively produces prostaglandin E2 (PGE2) and granulocyte-macrophage colony stimulating factor (GM-CSF). Epidermal Langerhans cells were found to have a decreased responsiveness to bacterial superantigen and to defined antigens in tumor-bearing mice, and also showed an impaired ability to induce proliferative responses in syngeneic or allogeneic responder T cells. Flow cytometric analysis revealed that the Langerhans cells of tumor bearers had decreased densities of the Ia molecule on their surfaces. No defects were observed in the potential of keratinocytes from tumor bearers to produce granulocyte-macrophage colony stimulating factor or to support the activation of syngeneic T cells. Incubation of normal Langerhans cells with tumor derived factors depressed their capacity to stimulate T cell syngeneic responses. Addition of indomethacin and anti-prostaglandin E2 did not reverse this depressed activity. These results indicate that epidermal Langerhans cells from tumor-bearing mice possess a functional deficit in acquiring accessory properties in vitro, which cannot be ascribed to a lack of GM-CSF in the local microenvironment or to production of inhibitory cytokines by their keratinocytes. The functional deficit of epidermal Langerhans cells of tumor-bearing mice may account for the depressed delayed hypersensitivity displayed by these mice, and factors elaborated by the tumor may be responsible for the deficiencies observed.

Aberrant antigen presentation by macrophages from tumor-bearing mice is involved in the down-regulation of their T cell responses

Splenic T cells from BALB/c mice bearing mammary adenocarcinomas initially demonstrate a primed response to tumor-associated Ags (TAA), which declines to presensitization levels within 4 wk after tumor implantation. Associated with this decline in responses to TAA is the expansion of a subpopulation of Mac-1+ 2+ splenic macrophages (M phi). These Mac-1+ 2+ cells present TAA inefficiently to normal T cells primed to TAA by footpad injection, as compared with the Ag presenting ability of M phi from normal mice. The addition of anti-I-Ed, but not anti-I-Ad, Ab blocked the ability of Ag-pulsed Mac-1+ 2+ cells to present TAA to primed T cells. The converse was observed with macrophages from normal mice. However, presentation of human gamma-globulin or OVA was restricted by I-Ad molecules when APC from normal mice or tumor bearers were used, although less efficiently in the latter. Using cell depletion techniques, it was determined that the I-Ed-restricted presentation preferentially expanded CD8+ T cells, and not CD4+ cells, as was the case for I-Ad-restricted normal macrophages. These CD8+ cells were poor effectors of cytotoxicity against tumor cells; instead they down-regulated the proliferative activity of T cells. Limiting dilution assays indicated that Mac-1+ 2+ macrophages preferentially present TAA to a low frequency inhibitory T cell population that expanded and inhibited further responses to TAA. Thus, alterations of Ag presentation in tumor bearers may help the tumor to subvert potential beneficial host responses and allow the progression of the neoplastic process.

Aberrant antigen presentation by macrophages from tumor-bearing mice is involved in the down-regulation of their T cell responses

Splenic T cells from BALB/c mice bearing mammary adenocarcinomas initially demonstrate a primed response to tumor-associated Ags (TAA), which declines to presensitization levels within 4 wk after tumor implantation. Associated with this decline in responses to TAA is the expansion of a subpopulation of Mac-1+ 2+ splenic macrophages (M phi). These Mac-1+ 2+ cells present TAA inefficiently to normal T cells primed to TAA by footpad injection, as compared with the Ag presenting ability of M phi from normal mice. The addition of anti-I-Ed, but not anti-I-Ad, Ab blocked the ability of Ag-pulsed Mac-1+ 2+ cells to present TAA to primed T cells. The converse was observed with macrophages from normal mice. However, presentation of human gamma-globulin or OVA was restricted by I-Ad molecules when APC from normal mice or tumor bearers were used, although less efficiently in the latter. Using cell depletion techniques, it was determined that the I-Ed-restricted presentation preferentially expanded CD8+ T cells, and not CD4+ cells, as was the case for I-Ad-restricted normal macrophages. These CD8+ cells were poor effectors of cytotoxicity against tumor cells; instead they down-regulated the proliferative activity of T cells. Limiting dilution assays indicated that Mac-1+ 2+ macrophages preferentially present TAA to a low frequency inhibitory T cell population that expanded and inhibited further responses to TAA. Thus, alterations of Ag presentation in tumor bearers may help the tumor to subvert potential beneficial host responses and allow the progression of the neoplastic process.

Detection of retroviral superantigen and products of the envelope gene from endogenous mouse mammary tumor virus in B cells from BALB/c mice

Minor lymphocyte-stimulating antigens and other superantigens have been shown to be encoded by the 3' long terminal repeat (LTR) open reading frame (ORF) of the endogenous and exogenous mammary tumor viruses. We have previously reported the presence of an antigen(s) related to mouse mammary tumor virus (MMTV) env products in splenic B cells of BALB/c mice. By Western blots an MMTV-related molecule of 68 kDa was detected in splenic preparations of B lymphocytes, but not in T cells. Antibodies against the MMTV envelope proteins gp52 and gp36, obtained by elution after binding to nitrocellulose in the presence of purified MMTV, reacted in Western blots with a 68-kDa protein present in B cells, indicating that this molecule is related to both MMTV envelope proteins. Using antibody against the MMTV 3' LTR ORF coding sequence, 10-15% of splenic B cells reacted by immunoperoxidase staining with this reagent, while no such staining was observed in splenic T cell preparations. Furthermore, in preparations of splenic B cells, but not T cells, two bands of 68 and 33 kDa, respectively, were detected by Western blots using the anti-ORF. These results demonstrate that the superantigen protein is present in B cells of BALB/c mice in two distinct forms, i.e., as a 68-kDa molecule, possibly associated with products of the env gene, and as a 33-kDa form.

Decreased macrophage-mediated cytotoxicity in mammary-tumor-bearing mice is related to alteration of nitric-oxide production and/or release

Peritoneal-exudate macrophages (PEM) from mammary-tumor-bearing mice have impaired cytotoxic activity against syngeneic and allogeneic tumor targets. The ability of PEM from normal and tumor-bearing mice to bind tumor targets was found to be similar in the presence or the absence of surrogate receptors, which enhanced the binding but not the killing of tumor targets by PEM from tumor-bearing mice, suggesting that other mechanisms are involved in their impaired cytolytic activity. Soluble and membrane-bound TNF-alpha, as well as H2O2, were found in higher amounts in PEM from tumor bearers upon stimulation with LPS, as compared with PEM from normal mice. However, tumor-bearers' macrophages displayed decreased capacity to produce and/or release nitric oxide, which could be reversed by the addition of increasing levels of IFN-gamma. These results indicate that the lack of macrophage cytotoxicity in mammary-tumor-bearing mice is related to impaired production and/or release of NO by these effector cells, possibly aggravated by the insufficient IFN-gamma production previously reported in these animals. Moreover, mammary-tumor progression results in dis-regulation of synthesis of macrophage-mediators, with over-production of molecules to which mammary-tumor cells are insensitive and deficient production of NO, the crucial molecule to which these cells appear to be highly sensitive.

A study of Helicobacter-pylori in 100 pediatric patients from the Tri-State area

Helicobacter pylori (HP) is a newly discovered pathogen implicated in the pathophysiology of peptic ulcer disease. The aim of this study was to review all pediatric patients who were evaluated by upper endoscopy through the Pediatric Gastroenterology Service at the Marshall University School of Medicine between July 1990 and March 1993. A total of 100 charts were retrospectively reviewed. HP was diagnosed by CLO-test and confirmed histologically. Results showed that the major presenting symptom was abdominal pain (53%). GI mucosal inflammation was found in 77 patients, and 41% of these cases were associated with HP. Two patients had duodenal ulcer; both were HP+. The incidence of gastritis was significantly higher in patients with HP+ compared to HP-. Follow-up on the HP-associated gastritis showed no significant difference in their clinical response irrespective to the treatment, we conclude that HP in children is highly associated with gastritis, but not duodenitis or esophagitis; and in our experience, that CLO has a high failure rate in identifying HP in the mucosa.

Isolation of a nitric oxide inhibitor from mammary tumor cells and its characterization as phosphatidyl serine

Macrophages from mice bearing large D1-DMBA-3 mammary tumors have a decreased capacity to kill tumor targets. This effect is due to an impaired ability to produce nitric oxide (NO) in response to lipopolysaccharide (LPS) stimulation. Here we report that the DA-3 tumor cell line, derived from the in vivo adenocarcinoma D1-DMBA-3, produces a factor that inhibits both NO production/release and cytotoxicity of LPS-activated peritoneal exudate macrophages (PEM). However, other complex macrophage functions such as phagocytosis, superoxide production, mitochondrial dehydrogenase activity, and synthesis of proteins were not reduced by this factor. The NO inhibitor has been found to be lipid in nature. Lipid extracts from DA-3 cell culture supernatants were purified by repeated silica gel column chromatography. The active molecule was unambiguously characterized as phosphatidyl serine (PS) by fast atom bombardment tandem mass spectrometry. Preliminary results indicate a lack of induced NO synthase (iNOS) activity in the lysates of LPS-activated PEM pretreated with PS. The ubiquity of PS in the inner leaflet of biological membranes and its NO inhibitory property, suggest that this phospholipid may be one of the long elusive molecules responsible for regulating physiological levels of NO in the host and hence preventing cellular dysfunction and/or tissue damage. Furthermore, the possible overexpression and shedding of PS by DA-3 tumor cells may represent a novel mechanism to impair macrophage cytotoxicity, a host function that contributes to the protection against developing neoplasms.

Noninvasive imaging of c-myc oncogene messenger RNA with indium-111-antisense probes in a mammary tumor-bearing mouse model

The c-myc oncogene is amplified in leukemia and solid tumors, thus making the c-myc messenger RNA (mRNA) a suitable target for following the progression of malignancy by noninvasive imaging with radiolabeled antisense pharmaceuticals or radiolabeled antisense oligodeoxynucleotide (RASON) probes. Considering the higher stability of phosphorothioate over phosphodiester, the probe stability and tumor localization was compared with both derivatives.

METHODS

The 15-mer oligonucleotide sequence was synthesized, aminolinked [sense and antisense phosphodiester (O) and monothioester (S)] and coupled with diethylenetriamine pentaacetate (DTPA)-isothiocyanate and aliquots were lyophilized to make a DTPAAHON kit. The radionuclide 111In was chelated to DTPAAHON derivatives, and free 111In was separated by gel filtration. The radiolabeled antisense and sense probes were injected intravenously in mammary tumor-bearing BALB/c mice (1 x 10(6) cells, 8 days postinoculation).

RESULTS

The highest uptake was observed at 2 hr with both thio and oxo derivatives of RASON probes, and small tumors could be imaged noninvasively. Tumor uptake and tumor/blood and tumor/muscle ratios for the sense probe (control) were significantly lower (p < 0.001) than those of the antisense probe.

CONCLUSION

The radiolabeled antisense probe may provide a new sensitive tool for noninvasive imaging of c-myc oncogene mRNA for a variety of malignant tumors at an earlier stage.

Soluble and membrane-bound TNF-alpha are involved in the cytotoxic activity of B cells from tumor-bearing mice against tumor targets

Splenic B cells from BALB/c mice bearing mammary adenocarcinomas are capable of performing Ab-dependent cellular cytotoxicity. Effector-target conjugation after 18 h results in minimal cytoplasmic damage, whereas extensive nuclear disintegration is observed. To determine whether splenic B cells from tumor-bearing mice can effect direct cytotoxicity against tumor cells, L929 and WEHI 164 cells were used as targets. B lymphocytes from tumor-bearing mice, but not from normal animals, were capable of lysing these two types of tumor cells. However, only a low level of cytotoxicity could be detected when the nontumorigenic 3T3 cells were used as targets. To elucidate the mechanism of cytotoxicity of these killer B cells, RNase protection assays were performed using perforin, granzyme A, TNF-alpha, and lymphotoxin probes. No perforin, granzyme A, or lymphotoxin RNA could be detected in purified preparations of B cells from normal and tumor-bearing mice. B cells from normal mice did not have TNF-alpha RNA. In contrast, B cells from tumor bearers expressed TNF-alpha RNA. TNF-alpha could be detected in supernatants from both unstimulated and stimulated tumor bearers' splenic B cells, as measured by ELISA, and its lytic activity was neutralized by anti-TNF-alpha Ab. Western blots revealed the presence of TNF-alpha on the surface of the killer B cells. Paraformaldehyde-fixed B cells from tumor-bearing mice but not from normal animals were able to lyse TNF-alpha-sensitive tumor targets. This cytotoxicity was neutralized by anti-TNF-alpha Ab. These results suggest that TNF-alpha in soluble and membrane-bound forms may be involved in the mechanism of cytotoxicity exerted by B cells from tumor-bearing mice.

Soluble and membrane-bound TNF-alpha are involved in the cytotoxic activity of B cells from tumor-bearing mice against tumor targets

Splenic B cells from BALB/c mice bearing mammary adenocarcinomas are capable of performing Ab-dependent cellular cytotoxicity. Effector-target conjugation after 18 h results in minimal cytoplasmic damage, whereas extensive nuclear disintegration is observed. To determine whether splenic B cells from tumor-bearing mice can effect direct cytotoxicity against tumor cells, L929 and WEHI 164 cells were used as targets. B lymphocytes from tumor-bearing mice, but not from normal animals, were capable of lysing these two types of tumor cells. However, only a low level of cytotoxicity could be detected when the nontumorigenic 3T3 cells were used as targets. To elucidate the mechanism of cytotoxicity of these killer B cells, RNase protection assays were performed using perforin, granzyme A, TNF-alpha, and lymphotoxin probes. No perforin, granzyme A, or lymphotoxin RNA could be detected in purified preparations of B cells from normal and tumor-bearing mice. B cells from normal mice did not have TNF-alpha RNA. In contrast, B cells from tumor bearers expressed TNF-alpha RNA. TNF-alpha could be detected in supernatants from both unstimulated and stimulated tumor bearers' splenic B cells, as measured by ELISA, and its lytic activity was neutralized by anti-TNF-alpha Ab. Western blots revealed the presence of TNF-alpha on the surface of the killer B cells. Paraformaldehyde-fixed B cells from tumor-bearing mice but not from normal animals were able to lyse TNF-alpha-sensitive tumor targets. This cytotoxicity was neutralized by anti-TNF-alpha Ab. These results suggest that TNF-alpha in soluble and membrane-bound forms may be involved in the mechanism of cytotoxicity exerted by B cells from tumor-bearing mice.

NK cells from mammary tumor bearing mice do not exert natural killer activity but function as antibody dependent cellular cytotoxicity effectors

We have previously found that natural killer (NK) activity is profoundly decreased in BALB/c mice bearing large mammary tumors. Kinetic studies showed that after 14 days of tumor implantation a reduction of 25-40% of NK cytotoxicity can be observed and by 21 days only very low levels of NK reactivity can be detected in the spleens of tumor bearers. Phenotypic analyses of the splenic NK cells of tumor bearing mice revealed that they have similar density, granularity and comparable levels of NK 2.1 antigen on their surfaces as compared to NK cells from normal mice. However, in tumor bearers there was a shift from a high surface asialo GM1-bearing NK population to low-density surface asialo GM1-positive bearing cells. Phenotypically characterized NK cells were quantitated to test the possibility that splenic NK cells from tumor bearers migrated to other organs and were therefore at lower levels in the spleen. No significant differences were observed in the percentages of NK cells from spleens from normal and tumor bearing mice. Using single cell conjugate assays it was found that there was no impairment in the capacity of NK from tumor bearers to bind the NK-sensitive Yac-1 cells, however, this event did not result in lysis of the target cells. To elucidate whether the lytic machinery of the tumor bearers' NK cells was inactivated, their capacity to effect antibody dependent cellular cytotoxicity (ADCC) was evaluated. In contrast to the results observed when NK activity was evaluated, NK cells from tumor bearing mice exerted higher levels of ADCC than their normal counterparts and they had a higher expression of Fc receptors on their surfaces. These results suggest that the depression of NK activity observed in tumor bearing mice occurs at a triggering step that is not necessary for the activation of the NK effectors via the Fc receptor and that no major impairment of the lytic machinery occurs during mammary tumorigenesis.

Regulation of leukocyte binding to endothelial tissues by tumor-derived GM-CSF

The adherence of leukocytes to endothelial cells is the first step in the migration of these cells into tumor tissues. Specific binding to the endothelial cells by leukocytes is mediated by the development and maintenance of adhesion molecules on the endothelium; however, the mechanisms of leukocyte traffic into tumors and of their interactions with neoplastic tissue are not clearly understood. The infiltration of leukocytes occurs in most spontaneous and transplanted solid tumors and we have previously reported that not only are murine mammary tumors heavily infiltrated by leukocytes but tumor-derived factors alter the development and function of leukocytes in tumor-bearing mice. We now present evidence that a tumor-derived cytokine, namely granulocyte-macrophage-colony-stimulating factor, appears to be of importance in the regulation of leukocyte binding to endothelial cells. The data suggest that tumor-derived factors may influence leukocyte trafficking within tumor tissue.

Role of tumor-derived cytokines on the immune system of mice bearing a mammary adenocarcinoma. II. Down-regulation of macrophage-mediated cytotoxicity by tumor-derived granulocyte-macrophage colony-stimulating factor

Peritoneal elicited macrophages (PEM) from mammary tumor-bearing mice have a decreased capacity to become cytotoxic against syngeneic, allogeneic, and xenogeneic target cells upon in vitro stimulation with LPS, as compared with PEM of normal mice. A regulatory mechanism other than PG release is suggested because the addition of both indomethacin and LPS to macrophage cultures from tumor-bearing mice caused no changes in their cytotoxic capability. Because tumor products have been implicated in the down-regulation of immune responses, we investigated whether pretreatment with supernatants from the tumor cell line DA-3, derived from the in vivo mammary adenocarcinoma D1-DMBA-3, affects the cytolytic capacity of macrophages. This treatment inhibits, in a dose-dependent fashion, the ability of stimulated normal PEM to kill target cells. Partial purification of DA-3 cell line supernatant showed that most of the inhibitory activity was exerted by factors with a molecular mass greater than 10 kDa and less than 30 kDa. However, slight inhibition could also be observed with fractions containing molecules less than 10 kDa. The data suggest that more than one factor released by the mammary tumor cells may be involved in the down-regulation of macrophage-mediated cytotoxicity. Because the DA-3 cells constitutively produce granulocyte-macrophage CSF (GM-CSF), which has a molecular mass of 27 kDa, we pretreated PEM from normal mice in vitro with rGM-CSF for 24 h. This resulted in a dose-dependent decrease in their capacity to kill tumor target cells upon LPS stimulation. Furthermore, PEM from normal mice injected with rGM-CSF for 25 days displayed a profound decrease in their cytolytic ability against DA-3 targets upon in vitro stimulation with increasing amounts of LPS. The pretreatment of PEM from normal mice with a combination of DA-3 cell supernatants and specific anti-GM-CSF partially neutralized the inhibitory effect of the DA-3 supernatant on macrophage tumoricidal capability. These results indicate that tumor-derived GM-CSF is an important factor involved in the decreased macrophage cytotoxicity during mammary adenocarcinoma progression.

Role of tumor-derived cytokines on the immune system of mice bearing a mammary adenocarcinoma. II. Down-regulation of macrophage-mediated cytotoxicity by tumor-derived granulocyte-macrophage colony-stimulating factor

Peritoneal elicited macrophages (PEM) from mammary tumor-bearing mice have a decreased capacity to become cytotoxic against syngeneic, allogeneic, and xenogeneic target cells upon in vitro stimulation with LPS, as compared with PEM of normal mice. A regulatory mechanism other than PG release is suggested because the addition of both indomethacin and LPS to macrophage cultures from tumor-bearing mice caused no changes in their cytotoxic capability. Because tumor products have been implicated in the down-regulation of immune responses, we investigated whether pretreatment with supernatants from the tumor cell line DA-3, derived from the in vivo mammary adenocarcinoma D1-DMBA-3, affects the cytolytic capacity of macrophages. This treatment inhibits, in a dose-dependent fashion, the ability of stimulated normal PEM to kill target cells. Partial purification of DA-3 cell line supernatant showed that most of the inhibitory activity was exerted by factors with a molecular mass greater than 10 kDa and less than 30 kDa. However, slight inhibition could also be observed with fractions containing molecules less than 10 kDa. The data suggest that more than one factor released by the mammary tumor cells may be involved in the down-regulation of macrophage-mediated cytotoxicity. Because the DA-3 cells constitutively produce granulocyte-macrophage CSF (GM-CSF), which has a molecular mass of 27 kDa, we pretreated PEM from normal mice in vitro with rGM-CSF for 24 h. This resulted in a dose-dependent decrease in their capacity to kill tumor target cells upon LPS stimulation. Furthermore, PEM from normal mice injected with rGM-CSF for 25 days displayed a profound decrease in their cytolytic ability against DA-3 targets upon in vitro stimulation with increasing amounts of LPS. The pretreatment of PEM from normal mice with a combination of DA-3 cell supernatants and specific anti-GM-CSF partially neutralized the inhibitory effect of the DA-3 supernatant on macrophage tumoricidal capability. These results indicate that tumor-derived GM-CSF is an important factor involved in the decreased macrophage cytotoxicity during mammary adenocarcinoma progression.

Expression of endogenous Mtv provirus transcripts in BALB/c splenic lymphocytes

The presence of antigen(s) related to the exogenous milk-transmitted murine mammary tumor virus on the surface of BALB/c splenic lymphocytes has been documented previously. Since the BALB/c strain lacks murine mammary tumor virus, the presence of murine mammary tumor virus-related antigen(s) on lymphocytes has been ascribed to expression of germinally transmitted Mtv transcripts and proviruses were characterized to evaluate this hypothesis. Transcripts from genomic size Mtv provirus(es) accumulated in the spleen in an age-dependent manner. Two novel Mtv transcripts of 7.8 and 6.4 kb were observed in the spleen. These observations indicate that the transcriptional and translational expression of an endogenous Mtv occurs in normal cells of the lymphoreticular lineage.

Splenic macrophages from tumor-bearing mice co-expressing MAC-1 and MAC-2 antigens exert immunoregulatory functions via two distinct mechanisms

Tumor burden has been shown to induce a variety of phenotypic and functional changes in the cellular constituents of the host's immune system. These changes have been implicated as mechanisms by which tumors avoid rejection. Studies of BALB/c mice bearing a D1-DMBA-3 mammary adenocarcinoma showed alterations of the splenocyte populations. There was a five-fold increase of macrophages (M phi) that were phenotypically and functionally analyzed to establish their role in tumor-induced modifications of the host's immune response. Monoclonal antibody staining defined a Mac-1+2+ population which comprised up to 20% of the splenocytes in tumor-bearers (TB), but is negligible in spleens from normal mice. These Mac-1+2+ M phi were found to mediate down-regulation of both polyclonal and antigen-specific T and B cell responses in vitro and in vivo. Although B cell responses were suppressed via prostaglandin E2 (PGE2) production by the TB M phi, T cell responses were relatively refractory to PGE2-mediated down-regulation. Instead, they were suppressed by a contact-dependent T cell-M phi interaction. Furthermore, tumor-derived factors such as granulocyte-M phi colony-stimulating factor (GM-CSF) seem to play an important role in the induction and expansion of the Mac-1+2+ M phi. These cells appear to mediate down-regulation of the host immune responses by at least two distinct mechanisms: 1) PGE2 production and 2) a cell contact-dependent, but non-major-histocompatibility-complex-specific, interaction.

The role of tumor-derived cytokines on the immune system of mice bearing a mammary adenocarcinoma. I. Induction of regulatory macrophages in normal mice by the in vivo administration of rGM-CSF

Using a dimethylbenzanthracene-induced immunogenic nonmetastatic murine mammary adenocarcinoma in BALB/c mice, our previous work has shown that splenocytes from tumor bearers have reduced responses to both mitogens and Ag including tumor-associated Ag. NK and cytotoxic T cell activities are also reduced in splenocytes of tumor bearers. Mac-1+2+ macrophages induced in mammary tumor bearers are capable of down-regulating lymphocyte responses to mitogens and tumor-associated Ag by cell to cell contact interaction and increased PGE2 production. We have found that the tumor constitutively releases a granulocyte-macrophage (GM)-CSF-like factor in vivo and in vitro, which may be responsible for the systemic increase in cells of the macrophage lineage in tumor-bearing mice. A tumor cell line established from the in vivo tumor expresses and releases GM-CSF as shown by Northern and Western blot analyses. Daily i.p. injections for 3 wk of 10,000 U of rGM-CSF into normal mice induces hemopoietic and immunologic alterations similar to those observed in tumor bearers. Mac-1+ and/or Mac-2+ macrophages can also be detected in the spleens and bone marrow of the mice treated with rGM-CSF. Additionally, splenocytes from rGM-CSF-treated mice have reduced responses to mitogens and their peritoneal exudate cells can cause in vitro down-regulation of proliferative responses of lymphocytes from normal mice. The suppression can be partially reversed by the addition of indomethacin to the cultures suggesting that PGE2 may contribute to the effect. rGM-CSF enhances the in vitro release of PGE2 by the spleen, bone marrow, and peritoneal cells of normal mice. These data indicate that the high levels of GM-CSF constitutively produced by the tumor may be responsible for the hemopoietic changes and immunologic alterations observed in tumor-bearing mice.

The role of tumor-derived cytokines on the immune system of mice bearing a mammary adenocarcinoma. I. Induction of regulatory macrophages in normal mice by the in vivo administration of rGM-CSF

Using a dimethylbenzanthracene-induced immunogenic nonmetastatic murine mammary adenocarcinoma in BALB/c mice, our previous work has shown that splenocytes from tumor bearers have reduced responses to both mitogens and Ag including tumor-associated Ag. NK and cytotoxic T cell activities are also reduced in splenocytes of tumor bearers. Mac-1+2+ macrophages induced in mammary tumor bearers are capable of down-regulating lymphocyte responses to mitogens and tumor-associated Ag by cell to cell contact interaction and increased PGE2 production. We have found that the tumor constitutively releases a granulocyte-macrophage (GM)-CSF-like factor in vivo and in vitro, which may be responsible for the systemic increase in cells of the macrophage lineage in tumor-bearing mice. A tumor cell line established from the in vivo tumor expresses and releases GM-CSF as shown by Northern and Western blot analyses. Daily i.p. injections for 3 wk of 10,000 U of rGM-CSF into normal mice induces hemopoietic and immunologic alterations similar to those observed in tumor bearers. Mac-1+ and/or Mac-2+ macrophages can also be detected in the spleens and bone marrow of the mice treated with rGM-CSF. Additionally, splenocytes from rGM-CSF-treated mice have reduced responses to mitogens and their peritoneal exudate cells can cause in vitro down-regulation of proliferative responses of lymphocytes from normal mice. The suppression can be partially reversed by the addition of indomethacin to the cultures suggesting that PGE2 may contribute to the effect. rGM-CSF enhances the in vitro release of PGE2 by the spleen, bone marrow, and peritoneal cells of normal mice. These data indicate that the high levels of GM-CSF constitutively produced by the tumor may be responsible for the hemopoietic changes and immunologic alterations observed in tumor-bearing mice.

Expansion of immunoregulatory macrophages by granulocyte-macrophage colony-stimulating factor derived from a murine mammary tumor

Using an immunogenic nonmetastatic murine mammary adenocarcinoma (D1-DMBA-3) induced in BALB/c mice by dimethylbenzanthracene, we have previously shown that splenocytes from tumor bearers have depressed lymphocyte responses to mitogens and antigens, including tumor-associated antigens. In addition, they display decreased natural killer and T-cell cytotoxic activities. Macrophages from tumor-bearing mice appear to be responsible for the suppression of T- and B-cell responses to concanavalin A, lipopolysaccharide, and tumor-associated antigens observed in tumor bearers. The appearance of these macrophages in the spleen tightly parallels the progressive growth of the tumor and the concomitant immunosuppression. Simultaneously high levels of macrophage progenitors were observed in blood, bone marrow, lung, and liver. A significant increase of colony-stimulating activity of the granulocyte-macrophage lineage was detected in the sera from tumor-bearing mice. Higher levels of this colony-stimulating activity (CSA) were detected in tumor cystic fluid as compared with the levels in serum. A tumor cell line established in vitro from the D1-DMBA-3 in vivo tumor produces high levels of a factor with CSA in culture supernatant fluids. Partial purification of the CSA from the tumor cell line supernatants was achieved using CentriCell ultrafiltration and SephacrylS-300 chromatography. These studies revealed that the molecular weight of the colony-stimulating-like factor is 32,000 to 35,000. The morphology of the colonies obtained in cultures using this factor is similar to that of the colonies that develop in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) but not with macrophage colony-stimulating factor (M-CSF). CSA from tumor cell supernatants was neutralized by antiserum to GM-CSF but not with anti-M-CSF or anti-granulocyte colony-stimulating factor (G-CSF). Macrophages from bone marrow or peritoneal exudates from normal mice cultured with tumor supernatant for 2 to 3 days strongly inhibit normal splenocyte responses to concanavalin A and lipopolysaccharide. The data suggest that the tumor releases a GM-CSF that alters the hemopoietic system and induces or expands macrophages, which exert a suppressive function on the immune system of tumor-bearing mice.

Thymic involution and thymocyte phenotypic alterations induced by murine mammary adenocarcinomas

A profound thymic atrophy has been observed in mice bearing large adenocarcinomas of the mammary gland. Only 2 to 5% of thymocytes remained 4 wk after tumor implantation. Although there is a slight decrease in the overall percentages of Thy-1+ cells in tumor bearers, the majority of the remaining cells are of a Thy-1 low phenotype. There was a lower percentage of double positive (CD4+, CD8+) cells, an increase of CD4+ CD8- thymocytes, similar percentages of CD4- CD8+ cells and double negative (CD4- CD8-) thymocytes in tumor-bearing mice. In addition, an increased percentage of CD3 cells could be detected in these animals. These results indicate that proportionally less immature thymocytes are present in the atrophic thymuses of mammary tumor bearers. Enhanced levels of glucocorticoids are known to produce similar effects on the thymus. However, adrenalectomy of mice followed by tumor implantation did not result in reversal of the thymic atrophy. Furthermore, a study of serum corticosterone levels in tumor bearers indicated no significant changes during tumorigenesis. A study of several parameters of bone marrow (BM) populations indicate that there is an increase in cells of the granulocyte-macrophage lineage and a decrease in lymphocytes induced by tumor-derived granulocyte macrophage-CSF. An alteration of prothymocytes in the BM is not the main cause of the thymic atrophy because BM cells from normal and tumor-bearing mice reconstituted irradiated normal mice equally well. There was no preferential recruitment of double positive cells to the spleen as indicated by no significant differences in the levels of T cells of immature phenotype including the CD4+ CD8+ population in the spleens of tumor bearers. Because no major changes were observed in tumor bearers, either at their capacity to repopulate the thymus or at the patterns of subsequent redistribution of thymocytes, it was postulated that the thymic atrophy may be caused by a direct or indirect effect of the tumor or tumor-associated factor(s). Intrathymic injections of tumor cells into young normal recipient mice resulted in a significant reduction of the thymus weight and cellularity. These data suggest that mammary tumors can secrete factor(s) that are capable of severely impairing the normal development of cells of the T cell lineage.

Thymic involution and thymocyte phenotypic alterations induced by murine mammary adenocarcinomas

A profound thymic atrophy has been observed in mice bearing large adenocarcinomas of the mammary gland. Only 2 to 5% of thymocytes remained 4 wk after tumor implantation. Although there is a slight decrease in the overall percentages of Thy-1+ cells in tumor bearers, the majority of the remaining cells are of a Thy-1 low phenotype. There was a lower percentage of double positive (CD4+, CD8+) cells, an increase of CD4+ CD8- thymocytes, similar percentages of CD4- CD8+ cells and double negative (CD4- CD8-) thymocytes in tumor-bearing mice. In addition, an increased percentage of CD3 cells could be detected in these animals. These results indicate that proportionally less immature thymocytes are present in the atrophic thymuses of mammary tumor bearers. Enhanced levels of glucocorticoids are known to produce similar effects on the thymus. However, adrenalectomy of mice followed by tumor implantation did not result in reversal of the thymic atrophy. Furthermore, a study of serum corticosterone levels in tumor bearers indicated no significant changes during tumorigenesis. A study of several parameters of bone marrow (BM) populations indicate that there is an increase in cells of the granulocyte-macrophage lineage and a decrease in lymphocytes induced by tumor-derived granulocyte macrophage-CSF. An alteration of prothymocytes in the BM is not the main cause of the thymic atrophy because BM cells from normal and tumor-bearing mice reconstituted irradiated normal mice equally well. There was no preferential recruitment of double positive cells to the spleen as indicated by no significant differences in the levels of T cells of immature phenotype including the CD4+ CD8+ population in the spleens of tumor bearers. Because no major changes were observed in tumor bearers, either at their capacity to repopulate the thymus or at the patterns of subsequent redistribution of thymocytes, it was postulated that the thymic atrophy may be caused by a direct or indirect effect of the tumor or tumor-associated factor(s). Intrathymic injections of tumor cells into young normal recipient mice resulted in a significant reduction of the thymus weight and cellularity. These data suggest that mammary tumors can secrete factor(s) that are capable of severely impairing the normal development of cells of the T cell lineage.

Nuclear disintegration of target cells by killer B lymphocytes from tumor-bearing mice

Normal murine B lymphocytes are not known to be effectors of the Fc receptor-mediated, antibody-dependent cellular cytotoxicity (ADCC). In contrast, we report here that highly purified splenic B cells from mammary tumor-bearing mice develop the potential of lysing antibody-coated target cells. These lymphocytes are characterized by being G-10 nonadherent, nylon wool adherent, sIg+, FcR+, Thy 1.2-, asialo GM1-, and the immunoglobulin heavy-chain genes of both chromosomes are rearranged. The lytic reaction is characterized by a noninterdigitating binding and by the appearance of endocytotic vesicles in the target cells. Nuclear disintegration occurs 18 h after initial effector-target cell conjugate formation. At such time, only minor cytoplasmic membrane alterations are evident. The emergence of killer B cells in tumor-bearing hosts indicates that all lymphoreticular cell types bearing Fc receptors are capable of mediating ADCC.

Thymic atrophy induced by murine mammary adenocarcinoma in vivo

The thymic compartment of mammary tumor bearing mice is severely affected with increasing tumor growth. T cell functions in peripheral organs are greatly impaired or absent in such animals. A study of the thymus in relation to tumorigenesis revealed a profound decrease in size accompanied by a disrupture of the normal thymic architecture. Although a strong splenic suppressor cell activity can be detected in this animal model, splenectomy did not prevent thymic involution. Injection of tumor associated factors into normal mice resulted in a thymic atrophy similar to that seen in tumor bearing mice. These findings indicate that the observed thymic involution may not be only due to stress-related phenomena but also a direct effect of the tumor.

Emergence of a B lymphocyte population with ADCC effector function in mammary tumor bearing mice

Differential expression of antibody dependent cellular cytotoxicity (ADCC) effectors was studied in normal Balb/cCrgI mice and those bearing a chemically induced 7, 12 dimethylbenzanthracene mammary adenocarcinoma. Depletion of macrophages from normal mouse splenocytes by Sephadex G-10 columns resulted in elimination of ADCC. Further separation of the normal G-10 nonadherent splenocytes on nylon wool columns did not result in any population with significant cytotoxicity. However, Balb/c mice bearing mammary tumors showed enhanced levels of ADCC which were not eliminated by macrophage removal. Lymphocytes from tumor bearers further separated on nylon wool yielded nonadherent and adherent populations both capable of effecting significant ADCC. Treatment of the nylon nonadherent cells of both normal and tumor bearing mice with anti-asialo GM1 (AGM1) and complement decreased the ADCC responses. The same treatment only marginally affected cytotoxic levels of nylon adherent cells from tumor bearers, indicating that these effectors are primarily of non-NK lineage. In addition, G-10 nonadherent, nylon adherent cells from tumor bearers separated on a fluorescence activated cell sorter based on the presence of surface immunoglobulins (slg) revealed that both the slg- and slg+ (98% pure) sorted cells were capable of functioning in ADCC. To determine whether in the tumor mice the 2% of slg- cells present in the slg+ sorted population were the ADCC effectors, mixing experiments were done in which up to 10% of slg- cells from tumor bearers were added to nylon adherent cells from normal mice. No significant increases in ADCC levels were found over that of normal mice. These experiments indicate that the 2% slg- cells were not the ADCC effectors nor were they inducing normal B cells to exert this type of cytotoxic reaction in vitro. To further substantiate the B cell lineage of the slg+ ADCC effectors, surface immunoglobulins were removed with protease treatment. After a 36 hr incubation, 92% of the cells had regenerated their slg. The results presented in this paper demonstrate that various splenic lymphoreticular populations from tumor bearers possess an enhanced cytolytic activity against antibody coated target cells. Among these is a unique nylon adherent slg+ cell that is capable of functioning as an ADCC effector.

Induction of "innocent bystander" cytotoxicity in nonimmune mice by adoptive transfer of L3T4+ Lyt-1+2- mammary tumor immune T-cells

Spleen cells from BALB/c mice, bearing a syngeneic mammary adenocarcinoma, nonspecifically lyse xenogeneic target cells following in vitro reexposure to mammary tumor-associated antigens. The effectors of this reaction have been shown to be Thy-1+ Lyt-1+2+ nylon-adherent cells. Tumor-immune spleen cells are also able to induce nonimmune spleen cells to express nonspecific cytotoxicity. Studies were undertaken to determine whether this inducer activity is mediated by the effector population or by a functionally distinct subset. Cell separation studies demonstrated that the inducers and effectors of innocent bystander cytotoxicity can be separated based upon the property of adherence to nylon wool. Further examination of the nylon-nonadherent inducer population indicated that the phenotype is L3T4 + Lyt-1+2-. By flow cytometry the inducer subset was shown to express a higher density of Thy 1 antigen than that expressed by the cytotoxic effectors. When adult thymectomized mice were implanted with mammary tumors, nonspecific effectors were not generated. In contrast, spleen cells from the same experimental animals were able to induce nonspecific cytotoxicity in normal mice following adoptive transfer of their spleen cells. Thus, these data support the conclusion that during the course of mammary tumor growth, at least two functionally and phenotypically distinct cell populations interact for the expression of "innocent bystander" cytotoxicity.

Dependence of initiation of an innocent bystander cytotoxicity reaction on the association of viral antigens and tumor cell membranes in mice

In chemically induced mouse mammary tumors in BALB/c mice, no murine mammary tumor virus (MuMTV) antigens could be detected in the tumor cell membranes. In contrast, in mammary tumors of spontaneous appearance in BALB/cfC3H mice neonatally infected with MuMTV, viral antigens could be detected by immunofluorescence. Specific activation of immune spleen lymphocytes in vitro by homologous tumor cell membrane preparations resulted in an innocent bystander cytotoxicity reaction in BALB/c mice bearing either the chemical- or virus-induced mammary tumors. Non-tumor bearers did not respond in this reaction. The cytotoxicity effector cell was a nylon-adherent Thy 1.2+, Lyt 1+, Lyt 2+ lymphocyte. Induction of the reaction in the chemically induced mammary tumor bearers was related to tumor-associated antigens, but in the mice with MuMTV-induced tumors, it was possible that all responses were solely due to viral antigens. Biochemical analyses using immunoprecipitation techniques indicated that the major external glycoprotein of MuMTV (gp52) was present in the tumor cell membrane preparations. Preincubation of the cell membranes of virus-induced tumors with anti-MuMTV completely blocked the capacity of this preparation to induce the cytotoxicity. Preabsorption of the anti-MuMTV with purified MuMTV removed all the blocking activity of these sera, indicating that the antigenic determinants recognized were of viral origin. However, purified MuMTV failed by itself to elicit the innocent bystander cytotoxicity. This observation indicates that an association with membranes was necessary for the viral antigens to initiate and/or effect this cell-mediated immune reaction.

Interaction of the heterozygous nude gene with the asplenia trait in mammary tumorigenesis

The BALB/c mouse strain has been shown to contain endogenous mouse mammary tumor virus (MMTV) proviral sequences. However, no exogenous MMTV particles have been detected in their tissues. Female BALB/c mice from our colonies exhibit a very low incidence of spontaneous mammary tumors (SMT); less than 1% at up to 20 mo of age. Immunodeficient BALB/c mice heterozygous for the nude gene (nu/+, +/+), for the dominant hemimelia gene associated with asplenia (+/+, Dh/+), or for both traits (nu/+, Dh/+) have been examined for SMT incidence and the presence of MMTV proviruses. Based on restriction digestion with Eco RI, Bam HI, and Pst I, the immunodeficient mice have an MMTV provirus copy number and organization identical to the BALB/cCrgl strain. This MMTV DNA pattern is distinct from the MMTV proviruses in C3H/He, C57BL/6J and CBA/CaJ mice, which were parental strains of the immunodeficient mutants. Normal female BALB/c or BALB/c heterozygous for the asplenic trait do not develop significant numbers of SMT at up to 19 mo of age. In contrast, an incidence of 23.8% and 57.7% SMT was observed in BALB/c nu/+ heterozygotes, and in BALB/c nu/+, Dh/+ heterozygotes, respectively. These results indicate that agenesis of the spleen, concomitant with the presence of the heterozygous nude gene, contribute to a high incidence of SMT in the low-SMT BALB/c mouse strain.

B cell subsets in spleens of BALB/c mice: identification and isolation of MMTV-expressing and MMTV-responding subpopulations

The DNA of BALB/c mice contains two genomic- and one subgenomic-size MMTV proviruses that appear to be preferentially expressed in their spleen cells, although intact MMTV virions cannot be detected in the tissues of these mice. This retrovirus antigen expression is restricted to a subpopulation of B lymphocytes, as determined by double label immunofluorescence studies. Nylon-adherent, SIg-positive spleen lymphocytes from BALB/c mice are capable of being stimulated by purified MMTV in lymphocyte transformation assays. Two possibilities were explored: the MMTV-positive cells are the responders to MMTV in the blastogenesis assay, or there exists two B lymphocyte subsets, one expressing the MMTV antigen(s) and the other responding to the virus. Depletion of MMTV-positive, nylon-adherent cells with anti-MMTV and complement resulted in no significant change in the blastogenesis to MMTV, indicating that the MMTV-negative lymphocytes are the responders in this reaction. These results were confirmed by positive selection experiments by using a fluorescence-activated cell sorter. Two populations of nylon-adherent cells, on the basis of the presence or absence of MMTV antigen in their surfaces, were obtained by a two-way sorting procedure and were used in lymphocyte transformation assays. MMTV-expressing lymphocytes were found to be nonresponsive to MMTV antigens, although high levels of [3H]thymidine incorporation were observed in the MMTV-negative, nylon-adherent cell cultures exposed to MMTV. These data indicate that in normal BALB/c mice, expression of endogeneous retrovirus genetic information is restricted to a nylon-adherent spleen cell subset that is different from the one responding in blastogenesis to the viral antigens.