Tradeoff between the Brillouin and transverse mode instabilities in Yb-doped fiber amplifiers.

The Brillouin instability (BI) due to stimulated Brillouin scattering (SBS) and the transverse (thermal) mode instability (TMI) due to stimulated thermal Rayleigh scattering (STRS) limit the achievable power in high-power lasers and amplifiers. The pump power threshold for BI increases as the core diameter increases, but the threshold for TMI may decrease as the core diameter increases. In this paper, we use a multi-time-scale approach to simultaneously model BI and TMI, which gives us the ability to find the fiber diameter with the highest power threshold. We formulate the equations to compare the thresholds of the combined and individual TMI and BI models. At the pump power threshold and below, there is a negligible difference between the full and individual models, as BI and TMI are not strong enough to interact with each other. The highest pump threshold occurs at the optimal core size of 43 µm for the simple double-clad geometry that we considered. We found that both effects contribute equally to the threshold, and the full BI and TMI model yields a similar threshold as the BI or TMI model alone. However, once the reflectivity is sufficiently large, we find in the full BI and TMI model that BI may trigger TMI and reduce the TMI threshold to a value lower than is predicted in simulations with TMI alone. This result cannot be predicted by models that consider BI and TMI separately. Our approach can be extended to more complex geometries and used for their optimization.

Accurate and efficient modeling of the transverse mode instability in high energy laser amplifiers.

We study the transverse mode instability (TMI) in the limit where a single higher-order mode (HOM) is present. We demonstrate that when the beat length between the fundamental mode and the HOM is small compared to the length scales on which the pump amplitude and the optical mode amplitudes vary, TMI is a three-wave mixing process in which the two optical modes beat with the phase-matched component of the index of refraction that is induced by the thermal grating. This limit is the usual limit in applications, and in this limit TMI is identified as a stimulated thermal Rayleigh scattering (STRS) process. We demonstrate that a phase-matched model that is based on the three-wave mixing equations can have a large computational advantage over current coupled mode methods that must use longitudinal step sizes that are small compared to the beat length.

Mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M) and serine biosynthetic pathway genes are co-ordinately increased during anabolic agent-induced skeletal muscle growth.

We aimed to identify novel molecular mechanisms for muscle growth during administration of anabolic agents. Growing pigs (Duroc/(Landrace/Large-White)) were administered Ractopamine (a beta-adrenergic agonist; BA; 20 ppm in feed) or Reporcin (recombinant growth hormone; GH; 10 mg/48 hours injected) and compared to a control cohort (feed only; no injections) over a 27-day time course (1, 3, 7, 13 or 27-days). Longissimus Dorsi muscle gene expression was analyzed using Agilent porcine transcriptome microarrays and clusters of genes displaying similar expression profiles were identified using a modified maSigPro clustering algorithm. Anabolic agents increased carcass (p = 0.002) and muscle weights (Vastus Lateralis: p < 0.001; Semitendinosus: p = 0.075). Skeletal muscle mRNA expression of serine/one-carbon/glycine biosynthesis pathway genes (Phgdh, Psat1 and Psph) and the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase-M (Pck2/PEPCK-M), increased during treatment with BA, and to a lesser extent GH (p < 0.001, treatment x time interaction). Treatment with BA, but not GH, caused a 2-fold increase in phosphoglycerate dehydrogenase (PHGDH) protein expression at days 3 (p < 0.05) and 7 (p < 0.01), and a 2-fold increase in PEPCK-M protein expression at day 7 (p < 0.01). BA treated pigs exhibit a profound increase in expression of PHGDH and PEPCK-M in skeletal muscle, implicating a role for biosynthetic metabolic pathways in muscle growth.

The global variability of diatomaceous earth toxicity: a physicochemical and in vitro investigation.

BACKGROUND: Diatomaceous earth (DE) is mined globally and is potentially of occupational respiratory health concern due to the high crystalline silica content in processed material. DE toxicity, in terms of variability related to global source and processing technique, is poorly understood. This study addresses this variability using physicochemical characterisation and in vitro toxicology assays. METHODS: Nineteen DE samples sourced from around the world, comprising unprocessed, calcined and flux-calcined DE, were analysed for chemical and mineral composition, particle size and morphology, and surface area. The potential toxicity of DE was assessed by its haemolytic capacity, and its ability to induce cytotoxicity or cytokine release by J774 macrophages. RESULTS: The potential toxicity of DE varied with source and processing technique, ranging from non-reactive to as cytotoxic and haemolytic as DQ12. Crystalline silica-rich, flux-calcined samples were all unreactive, regardless of source. The potential toxicity of unprocessed and calcined samples was variable, and did not correlate with crystalline silica content. Calcium-rich phases, iron content, amorphous material, particle size and morphology all appeared to play a role in sample reactivity. An increased surface area was linked to an increased reactivity in vitro for some sample types. CONCLUSIONS: Overall, no single property of DE could be linked to its potential toxicity, but crystalline silica content was not a dominant factor. Occlusion of the potentially toxic crystalline silica surface by an amorphous matrix or other minerals and impurities in the crystal structure are suggested to pacify toxicity in these samples. In vivo verification is required, but these data suggest that crystalline silica content alone is not a sufficient indicator of the potential DE hazard.

Toxicological effect of engineered nanomaterials on the liver.

The liver has a crucial role in metabolic homeostasis, as it is responsible for the storage, synthesis, metabolism and redistribution of carbohydrates, fats and vitamins, and numerous essential proteins. It is also the principal detoxification centre of the body, removing xenobiotics and waste products by metabolism or biliary excretion. An increasing number of studies have shown that some nanomaterials (NMs) are capable of distributing from the site of exposure (e.g. lungs, gut) to a number of secondary organs, including the liver. As a secondary exposure site the liver has been shown to preferentially accumulate NMs (>90% of translocated NMs compared with other organs), and alongside the kidneys may be responsible for the clearance of NMs from the blood. Research into the toxicity posed by NMs to the liver is expanding due to the realization that NMs accumulate in this organ following exposure via a variety of routes (e.g. ingestion, injection and inhalation). Thus it is critical to consider what advances have been made in the investigation of NM hepatotoxicity, as well as appraising the quality of the information available and gaps in the knowledge that still exist. The overall aim of this review is to outline what data are available in the literature for the toxicity elicited by NMs to the liver in order to establish a weight of evidence approach (for risk assessors) to inform on the potential hazards posed by NMs to the liver.

Effect of Nippostrongylus brasiliensis L3 ES on inflammatory mediator gene transcription in lipopolysaccharide lung inflammation.

The anti-inflammatory properties of parasitic helminths have been largely linked to their excretory-secretory (ES) products. Some studies have noted a lack of TNF-alpha production and limited recruitment of neutrophils into the lungs after Nippostrongylus brasiliensis infection. We previously reported that instillation of ES from L3 larvae of N. brasiliensis to the lungs could inhibit the recruitment of neutrophils on a background of LPS-induced inflammation. A similar reduction in neutrophil recruitment was observed in this study. This reduction was associated with the significant inhibition in gene transcription of the adhesion molecule, ICAM-1, and the chemokine, MIP-2 in bronchoalveolar lavage (BAL) cells. The LPS-stimulated gene transcription of the pro-inflammatory cytokines TNF-alpha and IL-1beta was also significantly reduced by L3 ES. Inducible nitric oxide synthase (iNOS) is normally elevated in classically activated macrophages, however, in this case gene transcription of iNOS was inhibited by L3 ES and may suggest a phenotype change to anti-inflammatory. The general inhibition of pro-inflammatory mediators observed in this study suggests that infective stage L3 larvae excrete and/or secrete inhibitory products capable of modifying the normally potent LPS inflammatory response.

Emerging impact of CTA/perfusion CT on acute stroke thrombolysis in a community hospital.

Our objective was to retrospectively review the emerging role of CT, CTA, and perfusion CT (pCT) in the hyperacute stroke population of a community hospital. We reviewed 50 consecutive patients' records and imaging studies, who were treated with thrombolytic therapy within 6 h of symptom onset. Multidetector CT, CTA, and pCT studies were evaluated. Subsequent CT, magnetic resonance, or angiographic studies when available were correlated. Patients' clinical data at admission and outcomes at discharge were evaluated. Complications were tabulated. Of the 50 patients treated with thrombolytics, 37 had CT/CTA/pCT, the others non-contrast CT only. CT blood volume defect was present in a total of 14 patients, presaging permanent infarct in all. Arterial clot was seen in 28/37 CTAs (carotid "T" 6, MCA 16, vertebrobasilar 6). Viable penumbra was shown in 20/37; rescued penumbra was depicted after treatment in 14. 39 patients were treated with intravenous, nine with intra-arterial, two with both forms of thrombolysis. Modified Rankin score showed clinical improvement in 58%, three patients had complete recovery. Subsequent bleed was shown in two (4%), symptomatic in one (2%). Two patients died. Our experience suggests advanced CT is more sensitive to ischemia than routine CT, that salvageable penumbra can be identified, and that triage of patients with acute stroke for thrombolysis with CT/CTA/pCT is more robust than routine CT alone, and may improve outcomes in the community hospital setting.

Measurement of reactive species production by nanoparticles prepared in biologically relevant media.

Exposure to nanoparticles may pose a risk to health and this hypothesis is currently being investigated by toxicologists. Although the mechanism of nanoparticle toxicity has been shown to be mediated, in part, by oxidative stress, the precise mechanism and molecules involved are still unknown. In light of this, the evaluation of the oxidative potential of nanoparticles is an important consideration in measuring their toxicity. The aim of this study was to examine the use of a fluorogenic probe, 2',7'-dichlorofluorescin (DCFH), in a cell-free assay system and to assess the relationship between the results obtained with this method and with the reactive species formation observed in cells. In order to obtain a well-dispersed nanoparticle suspension, bovine serum albumin (BSA) and dipalmitoyl phosphatidyl choline (DPPC) addition in suspension medium was investigated. Both 1% BSA and 0.025% DPPC added to the medium significantly improved the stability of the nanoparticle suspension, decreasing the extent of particle agglomeration and settling over time. In a cell-free system, reactive oxygen species (ROS) production by 14nm carbon black particles (CB) suspended in DPPC was higher than that measured with the other suspensions (saline or 1% BSA). A greater ROS production was observed in MonoMac 6 cells (MM6) following treatment with 14nm CB suspended in medium containing BSA and/or DPPC compared to medium alone. In conclusion, 1% BSA and 0.025% DPPC solution was the most efficient for the preparation of a nanoparticle suspension and to measure their oxidative potential.

Risk assessment of unsuitable winter conditions for manure and nutrient application across Ontario.

Practical guidelines addressing the timing of manure and nutrient application must consider the concerns of the farm operators while ensuring the protection of the environment. An approach was developed and analyzed through case studies to determine the first recommended day in the spring, and the last in the fall, for manure and nutrient application based on probability analysis. Since most manure and nutrient application guidelines recommend avoiding adverse conditions, the three criteria established to perform a risk assessment were: (i) a frost depth greater than 0.05 m; (ii) a snow accumulation of greater than 0.05 m; and (iii) a soil volumetric water content greater than or equal to that of the plastic limit for the soil. Climatic data and typical soil information for seven locations in Ontario were used to model volumetric soil water contents, frost depths, and snow accumulation from the simultaneous heat and water (SHAW) model for a 48-yr period (1954-2001). Applying the three criteria to the modeled output, the average range between the least limiting probability (0.1, or one in ten year occurrence) and the greatest limiting probability (0.001, or one in one thousand year occurrence) analyzed among the locations was 16 d in the spring as compared to 29 d in the fall. Although geographical location affected the predicted spring start and fall end recommended manure and nutrient application dates, local climate and soil hydraulic properties also played an important part in the determination of these days. Overall the prediction method developed performed reasonably well and provided insight into the environmental factors influencing manure and nutrient application timing.

The effect of oxidative stress on macrophages and lung epithelial cells: the role of phosphodiesterases 1 and 4.

Reactive oxygen species (ROS) have been implicated in various pulmonary diseases by causing direct injury to lung epithelial cells. Signalling activity of cells through transcription factors such as nuclear factor kappa B (NF-kappaB) and AP-1 have been shown to be regulated by ROS, and the release of pro-inflammatory cytokines demonstrated in the study of inflammatory disease. In this study, we examined the effect of the oxidant tert-butylhydroperoxide (tBHP) on mouse J774 macrophages and its ability to cause the release of the pro-inflammatory cytokine tumour necrosis factor alpha (TNF-alpha). The role of calcium as a signalling molecule was studied using various calcium antagonists. The role of the signalling molecule cAMP was also investigated using phosphodiesterase inhibitors PDE1 and PDE4 families. Oxidative stress was investigated in lung epithelial (A549) cells with and without calcium antagonists and PDE inhibitors with regard to their ability to modulate release of the neutrophil chemoattractant interleukin 8 (IL-8). The oxidant tBHP significantly increased the cytosolic calcium concentration in J774 macrophages, which was prevented by the PDE1 inhibitor. The production of TNF-alpha protein by J774 macrophages was mediated by a pathway involving calcium as addition of calcium antagonists inhibited the tBHP stimulated increase in the cytokine. Inhibitors of both PDE1 and PDE4 completely prevented the tBHP stimulated TNF-alpha release suggesting that the cAMP pathway may be important in the oxidant induced signalling pathway leading to gene expression of pro-inflammatory cytokines. In the presence of oxidant alone, A549 epithelial cells released significant amounts of IL-8, which was inhibited by both calcium antagonist treatment and PDE inhibition treatment. These data suggest that ROS-mediated lung inflammation could be mediated at least in part by calcium and elevated PDE activity associated with decreased cAMP in both macrophages and epithelial cells. Inhibition of these pathways may provide a route for treatment of inflammatory lung diseases.

Factors affecting attrition in a longitudinal study of patients with AIDS.

Anecdotal data have suggested that retention of HIV-infected patients with immune recovery in longitudinal studies may be difficult as they resume normal activities. This study evaluated risk factors for attrition among patients with AIDS in a cohort study in the era of highly active antiretroviral therapy. Patients with AIDS enrolled in the Longitudinal Study of Ocular Complications of AIDS were evaluated every three months with demographic, clinical and laboratory data collected. Lost to follow-up was defined as any patient who missed all study visits and could not be contacted for 12 consecutive months, who had not died and who did not re-enter the study at a later date. Of the 1,052 patients studied, 77 (7.3%) were lost to follow-up (rate = 0.03/person year). In the multivariate analysis, factors associated with attrition were CD4+ T-cell count category (hazard ratio (HR) = 2.03; 95%CI: 1.01, 4.24; P = 0.05 for CD4+ count < or = 50 cells/microL and HR = 1.96; 95%CI: 1.12, 3.40; P = 0.02 for CD4+ count 51-200 cells/microL) and detectable HIV viral load (HR = 1.29; 95%CI: 1.07, 1.53; P < 0.001 for HIV viral load >400 copies/mL). These data suggest that patients with compromised immunologic status are at an increased risk for being lost to follow-up.

Effects of PM10 in human peripheral blood monocytes and J774 macrophages.

The effects of PM10, one of the components of particulate air pollution, was investigated using human monocytes and a mouse macrophage cell line (J774). The study aimed to investigate the role of these nanoparticles on the release of the pro-inflammatory cytokine TNF-alpha and IL-1alpha gene expression. We also investigated the role of intracellular calcium signalling events and oxidative stress in control of these cytokines and the effect of the particles on the functioning of the cell cytoskeleton. We showed that there was an increase in intracellular calcium concentration in J774 cells on treatment with PM10 particles which could be significantly reduced with concomitant treatment with the calcium antagonists verapamil, the intracellular calcium chelator BAPTA-AM but not with the antioxidant nacystelyn or the calmodulin inhibitor W-7. In human monocytes, PM10 stimulated an increase in intracellular calcium which was reduced by verapamil, BAPTA-AM and nacystelyn. TNF-alpha release was increased with particle treatment in human monocytes and reduced by only verapamil and BAPTA-AM. IL-1alpha gene expression was increased with particle treatment and reduced by all of the inhibitors. There was increased F-actin staining in J774 cells after treatment with PM10 particles, which was significantly reduced to control levels with all the antagonists tested. The present study has shown that PM10 particles may exert their pro-inflammatory effects by modulating intracellular calcium signalling in macrophages leading to expression of pro-inflammatory cytokines. Impaired motility and phagocytic ability as shown by changes in the F-actin cytoskeleton is likely to play a key role in particle clearance from the lung.

Inhibition of neutrophil recruitment by ES of Nippostrongylus brasiliensis.

It has been reported that excretory-secretory (ES) material from the parasitic nematode Nippostrongylus brasiliensis has potential modulatory effects on the host's immune system. We observed that intratracheal instillation of ES from the L3 stage of the parasite reduced neutrophil numbers in LPS-induced inflammation as assessed by bronchoalveolar lavage.

Effect of coal mine dust and clay extracts on the biological activity of the quartz surface.

Modification of the quartz surface by aluminium salts and metallic iron have been shown to reduce the biological activity of quartz. This study aimed to investigate the ability of water soluble extracts of coal mine dust (CMD), low aluminium clays (hectorite and montmorillonite) and high aluminium clays (attapulgite and kaolin) to inhibit the reactivity of the quartz surface. DQ12 induced significant haemolysis of sheep erythrocytes in vitro and inflammation in vivo as indicated by increases in the total cell numbers, neutrophil cell numbers, MIP-2 protein and albumin content of bronchoalveolar lavage (BAL) fluid. Treatment of DQ12 with CMD extract prevented both haemolysis and inflammation. Extracts of the high aluminium clays (kaolin and attapulgite) prevented inhibition of DQ12 induced haemolysis, and the kaolin extract inhibited quartz driven inflammation. DQ12 induced haemolysis by coal mine dust and kaolin extract could be prevented by pre-treatment of the extracts with a cation chellator. Extracts of the low aluminium clays (montmorillonite and hectorite) did not prevent DQ12 induced haemolysis, although the hectorite extract did prevent inflammation. These results suggest that CMD, and clays both low and rich in aluminium, all contain soluble components (possibly cations) capable of masking the reactivity of the quartz surface.

Calcium and ROS-mediated activation of transcription factors and TNF-alpha cytokine gene expression in macrophages exposed to ultrafine particles.

Ultrafine (Uf) particles are a component of particulate air pollution suggested to be responsible for the health effects associated with elevations of this pollutant. We have previously suggested that Uf particles, through the induction of oxidative stress, may induce inflammation in the lung, thus exacerbating preexisting illness in susceptible individuals. Alveolar macrophages are considered to play a key role in particlemediated inflammation and lung disease. The effect of Uf particles on rat alveolar macrophages and human blood monocytes was investigated with reference to the roles of calcium and reactive oxygen species (ROS). TNF-alpha protein release, intracellular calcium concentration, TNF-alpha mRNA expression, and transcription factor activation were studied as end points after treatment of rat alveolar macrophages or peripheral blood monocytes. The calcium channel blocker verapamil, the intracellular calcium chelator BAPTA-AM, the calmodulin inhibitor W-7, and the antioxidants Trolox and Nacystelin (NAL) were included in combination with Uf particles. Verapamil reduced intracellular calcium concentration in rat alveolar macrophages on stimulation with Uf particles. This effect was also apparent with transcription factor AP-1 activation. All antagonists and antioxidants reduced Uf-stimulated nuclear localization of the p50 and p65 subunits of NF-kappaB in human monocytes. Verapamil, BAPTA-AM, and NAL reduced Uf-stimulated TNF-alpha protein release, whereas only verapamil reduced Uf-stimulated mRNA expression in rat alveolar macrophages. In human monocytes, verapamil, Trolox, BAPTA-AM, and W-7 reduced Uf-stimulated TNF-alpha protein release. These findings suggest that Uf particles may exert proinflammatory effects by modulating intracellular calcium concentrations, activation of transcription factors, and cytokine production through a ROS-mediated mechanism.

Aluminium lactate treatment of DQ12 quartz inhibits its ability to cause inflammation, chemokine expression, and nuclear factor-kappaB activation.

In 1997, an IARC Working Group classified quartz (crystalline silica) as a Group 1 lung carcinogen, but only in some industries, i.e., the quartz hazard is a variable entity. The reactivity of the quartz surface may underlie its ability to cause inflammation, and treatments that ameliorate this reactivity will reduce the quartz hazard. In this study we treated quartz (Q) with aluminium lactate (AL), a procedure that is reported to decrease the quartz hazard, and explored the effect this had on the highly reactive quartz surface and on proinflammatory events in rat lungs. Aluminium lactate-treated quartz showed a reduced surface reactivity as measured by electron spin resonance and the hemolysis assay. Eighteen hours after instillation of Q into the rat lung, there was massive inflammation as indicated by the number of neutrophils in the bronchoalveolar lavage (BAL). In addition, Q induced an increase in BAL macrophage inflammatory protein-2 (MIP-2) while ALQ had no significant effect compared to control. Epithelial damage, as indicated by BAL protein and gamma glutamyl transpeptidase, also increased with Q but not with ALQ. Furthermore, Q induced an increase in MIP-2 mRNA by BAL cells while ALQ had no effect compared to controls. There was an increase in nuclear binding of the transcription nuclear factor kappaB (NF-kappaB) in the Q-exposed BAL cells and again no effect on nuclear NF-kappaB binding in BAL cells from ALQ-exposed rats. In conclusion, treatment of the quartz surface with aluminium lactate reduced the reactivity of the particles both in terms of hydroxyl radical generation and in terms of the induction of molecular signaling events leading to inflammation.

Size-dependent proinflammatory effects of ultrafine polystyrene particles: a role for surface area and oxidative stress in the enhanced activity of ultrafines.

Studies into the effects of ultrafine particles in the lung have shown adverse effects considered to be due in part to the particle size. Air pollution particles (PM(10)) are associated with exacerbations of respiratory disease and deaths from cardiovascular causes in epidemiological studies and the ultrafine fraction of PM(10) has been hypothesized to play an important role. The aim of the present study was to investigate proinflammatory responses to various sizes of polystyrene particles as a simple model of particles of varying size including ultrafine. In the animal model, we demonstrated that there was a significantly greater neutrophil influx into the rat lung after instillation of 64-nm polystyrene particles compared with 202- and 535-nm particles and this was mirrored in other parameters of lung inflammation, such as increased protein and lactate dehydrogenase in bronchoalveolar lavage. When surface area instilled was plotted against inflammation, these two variables were directly proportional and the line passed through zero. This suggests that surface area drives inflammation in the short term and that ultrafine particles cause a greater inflammatory response because of the greater surface area they possess. In vitro, we measured the changes in intracellular calcium concentration in mono mac 6 cells in view of the potential role of calcium as a signaling molecule. Calcium changes after particle exposure may be important in leading to proinflammatory gene expression such as chemokines. We demonstrated that only ultrafine polystyrene particles induced a significant increase in cytosolic calcium ion concentration. Experiments using dichlorofluorescin diacetate demonstrated greater oxidant activity of the ultrafine particles, which may explain their activity in these assays. There were significant increases in IL-8 gene expression in A549 epithelial cells after treatment with the ultrafine particles but not particles of other sizes. These findings suggest that ultrafine particles composed of low-toxicity material such as polystyrene have proinflammatory activity as a consequence of their large surface area. This supports a role for such particles in the adverse health effects of PM(10).

Management of neurocytomas: case report and review of the literature.

The purpose of this report is to review the available literature on the presentation, pathology, and treatment of central nervous system (CNS) neurocytomas. A case report of an extraventricular neurocytoma is presented along with a comprehensive literature search of patients with a diagnosis of CNS neurocytoma. CNS neurocytomas are rare neoplasms, with fewer than 240 cases reported in the literature. The majority of neurocytomas are found in the ventricular system of the brain. Immunohistochemistry is frequently used to help distinguish this tumor from other CNS neoplasms. MIB-1 proliferation index is commonly used in an attempt to predict biologic behavior. Little is known about the management of patients with this tumor, because most reports are from the pathologic literature and contain sparse information regarding clinical management. Neurocytomas are rare CNS tumors with varied biologic behavior. MIB-1 index may help direct adjuvant therapy. An excellent prognosis can be expected if a gross total resection is achieved. Postoperative radiation therapy (RT) may be considered after subtotal resection. Otherwise, RT is an option for medically inoperable or recurrent disease.

Tumours can act as adjuvants for humoral immunity.

Tumour cells transfected with cDNAs encoding non-self proteins were used to investigate the ability of the immune system to respond to immunogenic antigens expressed by tumours. Secreted, intracellular and surface proteins were used as model antigens, as these reflect the potential forms of tumour antigens. Syngeneic BALB/c mice injected with viable line 1 lung carcinoma or EMT6 mammary tumour cells secreting ovalbumin (OVA) or prostate-specific antigen (PSA) produced very high immunoglobulin G (IgG) antibody titres, equivalent to those of mice injected with protein in Freund's complete adjuvant (FCA). Secretion of the antigens was not necessary as tumour cells expressing a cell-surface antigen (HER-2/Neu) or an intracellular antigen - green fluorescence protein (GFP) - also generated high-titre antigen-specific IgG antibodies. In interleukin-4 (IL-4)-deficient mice, both IgG1 and IgG2a were produced in response to OVA administered in FCA, whereas in response to tumour-produced antigen, the antibodies switched from predominantly IgG1 to IgG2a, indicating that the mechanisms responsible for antibody induction differed between these forms of immunization. In contrast to the line 1 and EMT6 tumours, which are of BALB/c origin, OVA- or PSA-producing B16 melanoma cells, which are of C57BL/6 origin, failed to elicit antibody production. This was not the result of strain differences, as a similar finding was observed when the tumours were grown in (BALB/c x C57BL/6)F1 mice, but appeared to be caused by intrinsic differences in the tumours. Furthermore, co-injection of both B16/OVA and line 1 tumours resulted in production of anti-OVA antibody, indicating that B16 tumours were not immunosuppressive, but instead line 1 tumours appear to exert an adjuvant effect.