Toxic effects of mineral oil saturated hydrocarbons (MOSH) and relation to accumulation in rat liver

Humans are daily exposed to mineral oil saturated hydrocarbons (MOSH) from the diet. We exposed female Fischer 344 rats to a broad mixture and sub-fractions of MOSH. Chemical characterization of the MOSH mixture used and material accumulated in rat tissues were previously reported (Barp et al. 2017a, 2017b). Rats were exposed to feed containing 0-4000 mg/kg broad MOSH mixture for 30, 60, 90 and 120 days; and for 120 days to feed containing different MOSH fractions: i) mainly molecular masses < C25 (S-C25), ii) dewaxed, mainly molecular masses > C25 (L-C25) and iii) the L-C25 fraction mixed with wax largely consisting of n-alkanes > C25 (L-C25W). Treatments related effects were increased liver and spleen weight, as well as vacuolization and granuloma formation with lymphoid cell clusters in the liver, but effects varied strongly between the MOSH fractions tested. We conclude that increased liver and spleen weights were related to accumulated n-alkanes (wax) above C25, presumably not relevant for humans, but also to MOSH from S-C25, mainly consisting of iso-alkanes and substituted cycloalkanes below C25 with a small proportion of n-alkanes. Induction of liver granuloma appeared to be related to n-alkanes > C25 and not to the accumulated amount of MOSH. Immune responses to an injected antigen were not affected. Iso-alkanes and substituted cycloalkanes accumulating in rat liver and spleen were similar to those accumulating in humans.

Suspected gut barrier disruptors and development of food allergy: Adjuvant effects and early immune responses

Food allergy is an increasing public health challenge worldwide. It has recently been hypothesized that the increase in exposure to intestinal epithelial barrier-damaging biological and chemical agents contribute to this development. In animal models, exposure to adjuvants with a food allergen has been shown to promote sensitization and development of food allergy, and barrier disrupting capacities have been suggested to be one mechanism of adjuvant action. Here, we investigated how gut barrier disrupting compounds affected food allergy development in a mouse model of peanut allergy. Sensitization and clinical peanut allergy in C3H/HEOuJ mice were assessed after repeated oral exposure to peanut extract together with cholera toxin (CT; positive control), the mycotoxin deoxynivalenol (DON), house dust mite (HDM) or the pesticide glyphosate (GLY). In addition, we investigated early effects 4 to 48 h after a single exposure to the compounds by assessing markers of intestinal barrier permeability, alarmin production, intestinal epithelial responses, and local immune responses. CT and DON exerted adjuvant effects on peanut allergy development assessed as clinical anaphylaxis in mice. Early markers were affected only by DON, observed as increased IL-33 (interleukin 33) and thymic stromal lymphopoietin (TSLP) alarmin production in intestines and IL-33 receptor ST2 in serum. DON also induced an inflammatory immune response in lymph node cells stimulated with lipopolysaccharide (LPS). HDM and GLY did not clearly promote clinical food allergy and affected few of the early markers at the doses tested. In conclusion, oral exposure to CT and DON promoted development of clinical anaphylaxis in the peanut allergy mouse model. DON, but not CT, affected the early markers measured in this study, indicating that DON and CT have different modes of action at the early stages of peanut sensitization.

Perfluoroalkyl substances, airways infections, allergy and asthma related health outcomes - implications of gender, exposure period and study design

INTRODUCTION

Exposure to perfluoroalkyl substances (PFASs) has been inconsistently associated with asthma, allergic diseases and airways infections in early childhood. The aim of the study was, therefore, to investigate the effect of childhood exposure to PFASs on asthma and allergy related outcomes and on airways infections before and during puberty using the prospective birth cohort Environment and Childhood Asthma (ECA) Study. Aspects of gender, exposure period and study design (cross-sectional and longitudinal) were also taken into consideration.

MATERIAL AND METHODS

Included in the study was 378 participants with PFAS measurements at age 10 years and follow-up data at ages 10 years (cross sectional data) and 16 years (longitudinal data). Eight PFASs with at least 70% of measurements above the limit of quantification (LOQ) in the child's serum were included in the present study: perfluoroheptanoate (PFHpA), perfluorooctanoate (PFOA), perfluourononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA), perfluorohexane sulfonate (PFHxS), perfluoroheptane sulfonate (PFHpS) and perfluorooctane sulfonate (PFOS). The PFAS levels were converted into interquartile range (IQR). In addition, perfluorooctane sulfonamide (PFOSA) detected in 60% of the samples, was recoded into "not detected /detected". Binomial, multinomial and linear regression were used, followed by Bonferroni adjustment to correct for multiple comparisons. Sensitivity analyses evaluating the effect of extreme PFAS values and gender were performed.

RESULTS

In the cross sectional data at 10 years a positive statistically significant association was seen between PFHpA and asthma in girls. In the longitudinal data, PFNA, PFDA and PFUnDA were inversely associated with atopic dermatitis (AD) in girls and with PFHxS in all participants and in boys. Further, PFNA and PFHpS were positively associated with rhinitis in girls and with PFOA in all participants. There seems to be a suggestive pattern of increased risk of allergic sensitisation in all participants and a decreased risk in boys, but due to different results in main and sensitivity analyses these findings should be interpreted with caution. No associations were found between PFASs and lung function. For airways infections and longitudinal data, PFDA was inversely associated with common cold, while positive association was found for PFHpA, PFOA, PFHpS and PFOS and lower respiratory tract infections (LRTI).

DISCUSSION AND CONCLUSION

Our results lend further support for an immunosuppressive effect of PFASs on AD and LRTI. Gender seems to be important for some exposure-health associations. No clear pattern in exposure-health associations was observed with regard to exposure period or study design, with the exception of asthma where significant findings have mostly been reported in cross-sectional studies.

Maternal levels of perfluoroalkyl substances (PFASs) during pregnancy and childhood allergy and asthma related outcomes and infections in the Norwegian Mother and Child (MoBa) cohort

INTRODUCTION

Prenatal exposure to perfluoroalkyl substances (PFASs) has been inconsistently associated with asthma and allergic diseases and increased number of infections in early childhood. We examined the association of PFASs measured in pregnancy with childhood asthma, allergies and common infectious diseases in a prospective pregnancy cohort followed to age 7 years.

MATERIAL AND METHODS

Six PFASs (out of 19 measured) with at least 80% of measurements above the limit of quantification (LOQ) in maternal plasma during pregnancy in two subcohorts of the Norwegian Mother and Child Cohort Study (MoBa) were analyzed in relation to health outcomes: perfluorooctane sulfonic acid (PFOS), acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUnDA), and perfluoroheptane sulfonic acid (PFHpS). Follow-up questionnaires were completed at 3 years by 1270 women and at 7 years by 972 women among the 1943 with pregnancy questionnaire and PFAS measures. Health outcomes included parent reports of child's symptoms or doctor diagnosed asthma and allergic conditions at age 7 years and parent-reported frequency of various infections at 3 and 7 years of age. Logistic and Poisson regression were used. The false discovery rate was controlled at 5%. Sensitivity analyses on gender were performed.

RESULTS

Among the allergy and asthma outcomes, a statistically significant inverse association was seen between PFUnDA concentrations and ever having atopic eczema in girls. PFUnDA also tended to be inversely associated with both wheeze and asthma. For infections from 0 to 3 and 6 to 7 years, 11 significant positive associations were seen between PFASs and airways infections (bronchitis/pneumonia, throat infection, pseudocroup), ear infection and gastric flu/diarrhea; whereas 6 inverse associations were seen for pseudocroup, ear infections and urinary tract infections. The majority of the findings with respect to infectious diseases were found in girls only.

DISCUSSION

With the exception of an inverse association between PFUnDA and eczema, and a tendency of a similar association for wheeze and asthma, maternal PFAS levels during pregnancy showed little association with asthma or allergy related outcomes. Findings from the present study suggest immunosuppressive effects of PFASs on airways infections, such as bronchitis/pneumonia and throat infections, as well as diarrhea/gastric flu. Our results indicate a possible role of gender in the PFAS-health outcome associations.

Prenatal exposure to perfluoralkyl substances (PFASs) associated with respiratory tract infections but not allergy- and asthma-related health outcomes in childhood

BACKGROUND

Prenatal exposure to perfluoralkyl substances (PFASs) has been reported to be associated with immunosuppression in early childhood, but with contradictory findings related to atopic and lung diseases.

AIM

We aimed to determine if prenatal exposure to PFASs is associated with asthma or other allergic diseases or respiratory tract infections in childhood.

METHODS

Nineteen PFASs were measured in cord blood available from 641 infants in the Environment and Childhood Asthma (ECA) prospective birth cohort study. The six most abundant PFASs were perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonamide (PFOSA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and perfluoroundecanoic acid (PFUnDA). Health outcomes were assessed at two and ten years of age, and included reported obstructive airways disease (wheeze by 10 years; asthma by 2 and 10 years; reduced lung function at birth; allergic rhinitis by 10 years), atopic dermatitis (AD) by 2 and 10 years, allergic sensitization by 10 years, and episodes of common respiratory tract infections (common cold by 2 years, lower respiratory tract infections (LRTI) by 10 years). The associations between exposure and health outcomes were examined using logistic and Poisson regression.

RESULTS

The number of reported airways infections were significantly associated with cord blood concentrations of PFAS; common colds by two years with PFUnDA (β = 0.11 (0.08-0.14)) and LRTIs from 0 to 10 years of age with PFOS (β = 0.50 (0.42-0.57)), PFOA (β = 0.28 (0.22-0.35)), PFOSA (β = 0.10 (0.06-0.14)), PFNA (β = 0.09 (0.03-0.14)) and PFUnDA (β = 0.18 (0.13-0.23)) concentrations. Neither reduced lung function at birth, asthma, allergic rhinitis, AD nor allergic sensitization were significantly associated with any of the PFASs.

CONCLUSION

Although prenatal exposure to PFASs was not associated with atopic or lung manifestations by 10 years of age, several PFASs were associated with an increased number of respiratory tract infections in the first 10 years of life, suggesting immunosuppressive effects of PFASs.

Exposure to perfluoroundecanoic acid (PFUnDA) accelerates insulitis development in a mouse model of type 1 diabetes

Perfluoralkylated substances (PFAS) are classified as persistent, bioaccumulative and toxic substances and are widespread environmental contaminants. Humans are exposed through food, drinking water and air. We have previously reported that bisphenol A accelerates spontaneous diabetes development in non-obese diabetic (NOD) mice and observed in the present study that perfluoroundecanoic acid, PFUnDA, increased insulitis development, a prerequisite for diabetes development in NOD mice. We exposed NOD mice to PFUnDA in drinking water (3, 30 and 300 μg/l) at mating, during gestation and lactation and until 30 weeks of age. After 300 μg/l PFUnDA exposure, we report (i) increased pancreatic insulitis, (ii) increased number of apoptotic cells in pancreatic islets prior to insulitis and (iii) decreased phagocytosis in peritoneal macrophages. There was also a trend of decreased number of tissue resident macrophages in pancreatic islets prior to insulitis after exposure to 300 μg/l, and altered cytokine secretion in activated splenocytes after exposure to 3 μg/l PFUnDA. Although insulitis is a prerequisite for autoimmune diabetes, the accelerated insulitis was not associated with accelerated diabetes development. Instead, the incidence of diabetes tended to be reduced in the animals exposed to 3 and 30 μg/l PFUnDA, suggesting a non-monotonic dose response. The effects of PFUnDA exposure on increased apoptosis in pancreas and reduced macrophage function as well as accelerated insulitis development in NOD mice, may also be relevant for human insulitis. Further observational autoimmune diabetes clinical cohort studies and animal experiments for PFUnDA as well as other PFASs are therefore encouraged.

Current challenges facing the assessment of the allergenic capacity of food allergens in animal models

Food allergy is a major health problem of increasing concern. The insufficiency of protein sources for human nutrition in a world with a growing population is also a significant problem. The introduction of new protein sources into the diet, such as newly developed innovative foods or foods produced using new technologies and production processes, insects, algae, duckweed, or agricultural products from third countries, creates the opportunity for development of new food allergies, and this in turn has driven the need to develop test methods capable of characterizing the allergenic potential of novel food proteins. There is no doubt that robust and reliable animal models for the identification and characterization of food allergens would be valuable tools for safety assessment. However, although various animal models have been proposed for this purpose, to date, none have been formally validated as predictive and none are currently suitable to test the allergenic potential of new foods. Here, the design of various animal models are reviewed, including among others considerations of species and strain, diet, route of administration, dose and formulation of the test protein, relevant controls and endpoints measured.

Investigations of immunogenic, allergenic and adjuvant properties of Cry1Ab protein after intragastric exposure in a food allergy model in mice

Background

In genetically modified (GM) crops there is a risk that the inserted genes may introduce new allergens and/or adjuvants into the food and feed chain. The MON810 maize, expressing the insecticidal Cry1Ab toxin, is grown in many countries worldwide. In animal models, intranasal and intraperitoneal immunisations with the purified Cry1Ab proteins have induced immune responses, and feeding trials with Cry1Ab-containing feed have revealed some altered immune responses. Previous investigations have primarily measured antibody responses to the protein, while investigations of clinical food allergy symptoms, or allergy promotion (adjuvant effect) associated with the Cry1Ab protein are largely missing. We aimed to investigate immunogenic, allergenic and adjuvant properties of purified Cry1Ab toxin (trypCry1Ab, i.e., trypsin activated Cry1Ab) in a mouse model of food allergy.

Method

Female C3H/HeJ mice were immunized by intragastric gavage of 10 μg purified, trypsin activated Cry1Ab toxin (trypCry1Ab) alone or together with the food allergen lupin. Cholera toxin was added as a positive control for adjuvant effect to break oral tolerance. Clinical symptoms (anaphylaxis) as well as humoral and cellular responses were assessed.

Results

In contrast to results from previous airway investigations, we observed no indication of immunogenic properties of trypCry1Ab protein after repeated intragastric exposures to one dose, with or without CT as adjuvant. Moreover, the results indicated that trypCry1Ab given by the intragastric route was not able to promote allergic responses or anaphylactic reactions against the co-administered allergen lupin at the given dose.

Conclusion

The study suggests no immunogenic, allergenic or adjuvant capacity of the given dose of trypCry1Ab protein after intragastric exposure of prime aged mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-016-0148-x) contains supplementary material, which is available to authorized users.

A Simple Pharmacokinetic Model of Prenatal and Postnatal Exposure to Perfluoroalkyl Substances (PFASs)

Most children are exposed to perfluoroalkyl substances (PFASs) through placental transfer, breastfeeding, and other environmental sources. To date, there are no validated tools to estimate exposure and body burden during infancy and childhood. In this study, we aimed to (i) develop a two-generation pharmacokinetic model of prenatal and postnatal exposure to perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), and perfluorohexanesulfonate (PFHxS); and to (ii) evaluate it against measured children's levels in two studies. We developed a pharmacokinetic model consisting of a maternal and a child compartment to simulate lifetime exposure in women and transfer to the child across the placenta and through breastfeeding. To evaluate the model, we performed simulations for each mother-child dyad from two studies in which maternal PFAS levels at delivery and children's PFAS levels were available. Model predictions based on maternal PFAS levels, sex of child, body weight, and duration of breastfeeding explained between 52% and 60% of the variability in measured children's levels at 6 months of age and between 52% and 62% at 36 months. Monte Carlo simulations showed that the daily intake through breastfeeding and resulting internal PFAS levels can be much higher in nursing infants than in mothers. This pharmacokinetic model shows potential for postnatal exposure assessment in the context of epidemiological studies and risk assessment.

Corrigendum to "Genetic and Diet-Induced Obesity Increased Intestinal Tumorigenesis in the Double Mutant Mouse Model Multiple Intestinal Neoplasia X Obese via Disturbed Glucose Regulation and Inflammation"

[This corrects the article DOI: 10.1155/2015/343479.]. In the published paper "Genetic and Diet-Induced Obesity Increased Intestinal Tumorigenesis in the Double Mutant Mouse Model Multiple Intestinal Neoplasia X Obese via Disturbed Glucose Regulation and Inflammation" [1] we mistakenly wrote IL-1β instead of IL-6 in Tables 2 and 3. In addition, IL-6 was not included in the text below the tables stating that it was measured by flow cytometer as was TNFα. The corrected tables are presented here.

Genetic and Diet-Induced Obesity Increased Intestinal Tumorigenesis in the Double Mutant Mouse Model Multiple Intestinal Neoplasia X Obese via Disturbed Glucose Regulation and Inflammation

We have studied how spontaneous or carcinogen-induced intestinal tumorigenesis was affected by genetic or diet-induced obesity in C57BL/6J-Apc (Min/+) X C57BL/6J-Lep (ob/+) mice. Obesity was induced by the obese (ob) mutation in the lep gene coding for the hormone leptin, or by a 45% fat diet. The effects of obesity were examined on spontaneous intestinal tumors caused by the multiple intestinal neoplasia (Min) mutation in the adenomatous polyposis coli (Apc) gene and on tumors induced by the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). F1 ob/ob (homozygous mutated) mice had increased body weight (bw) and number of spontaneous and PhIP-induced small intestinal tumors (in Apc (Min/+) mice), versus ob/wt (heterozygous mutated) and wt/wt mice (homozygous wild-type). A 45% fat diet exacerbated bw and spontaneous tumor numbers versus 10% fat, but not PhIP-induced tumors. Except for bw, ob/wt and wt/wt were not significantly different. The obesity caused hyperglucosemia and insulinemia in ob/ob mice. A 45% fat diet further increased glucose, but not insulin. Inflammation was seen as increased TNFα levels in ob/ob mice. Thus the results implicate disturbed glucose regulation and inflammation as mechanisms involved in the association between obesity and intestinal tumorigenesis. Ob/ob mice had shorter lifespan than ob/wt and wt/wt mice.

Polycyclic aromatic hydrocarbons, tobacco smoke, and epigenetic remodeling in asthma

Environmental determinants including aerosolized pollutants such as polycyclic aromatic hydrocarbons (PAHs) and tobacco smoke have been associated with exacerbation and increased incidence of asthma. The influence of aerosolized pollutants on the development of immune dysfunction in asthmatics has been suggested to be mediated through epigenetic remodeling. Genome accessibility and transcription are regulated primarily through DNA methylation, histone modification, and microRNA transcript silencing. Epigenetic remodeling has been shown in studies to be associated with Th2 polarization and associated cytokine and chemokine regulation in the development of asthma. This review will present evidence for the contribution of the aerosolized pollutants PAH and environmental tobacco smoke to epigenetic remodeling in asthma.

Micronuclei in cord blood lymphocytes and associations with biomarkers of exposure to carcinogens and hormonally active factors, gene polymorphisms, and gene expression: the NewGeneris cohort

BACKGROUND

Leukemia incidence has increased in recent decades among European children, suggesting that early-life environmental exposures play an important role in disease development.

OBJECTIVES

We investigated the hypothesis that childhood susceptibility may increase as a result of in utero exposure to carcinogens and hormonally acting factors. Using cord blood samples from the NewGeneris cohort, we examined associations between a range of biomarkers of carcinogen exposure and hormonally acting factors with micronuclei (MN) frequency as a proxy measure of cancer risk. Associations with gene expression and genotype were also explored.

METHODS

DNA and protein adducts, gene expression profiles, circulating hormonally acting factors, and GWAS (genome-wide association study) data were investigated in relation to genomic damage measured by MN frequency in lymphocytes from 623 newborns enrolled between 2006 and 2010 across Europe.

RESULTS

Malondialdehyde DNA adducts (M1dG) were associated with increased MN frequency in binucleated lymphocytes (MNBN), and exposure to androgenic, estrogenic, and dioxin-like compounds was associated with MN frequency in mononucleated lymphocytes (MNMONO), although no monotonic exposure-outcome relationship was observed. Lower frequencies of MNBN were associated with a 1-unit increase expression of PDCD11, LATS2, TRIM13, CD28, SMC1A, IL7R, and NIPBL genes. Gene expression was significantly higher in association with the highest versus lowest category of bulky and M1dG-DNA adducts for five and six genes, respectively. Gene expression levels were significantly lower for 11 genes in association with the highest versus lowest category of plasma AR CALUX® (chemically activated luciferase expression for androgens) (8 genes), ERα CALUX® (for estrogens) (2 genes), and DR CALUX® (for dioxins). Several SNPs (single-nucleotide polymorphisms) on chromosome 11 near FOLH1 significantly modified associations between androgen activity and MNBN frequency. Polymorphisms in EPHX1/2 and CYP2E1 were associated with MNBN.

CONCLUSION

We measured in utero exposure to selected environmental carcinogens and circulating hormonally acting factors and detected associations with MN frequency in newborns circulating T lymphocytes. The results highlight mechanisms that may contribute to carcinogen-induced leukemia and require further research.

Particles influence allergic responses in mice--role of gender and particle size

Epidemiological evidence suggesting that exposure to traffic air pollution may enhance sensitization to common allergens in children is increasing, and animal studies support biological plausibility and causality. The effect of air pollution on respiratory symptoms was suggested to be gender dependent. Previous studies showed that allergy-promoting activity of polystyrene particles (PSP) increased with decreasing particle size after footpad injection of mice. The primary aim of this study was to confirm the influence of particle size on the immunoglobulin E (IgE)-promoting capacity of particles in an airway allergy model. A second aim was to examine whether the allergy-promoting capacity of particles was influenced by gender. Female and male mice were intranasally exposed to the allergen ovalbumin (OVA) with or without ultrafine, fine, or coarse PSP modeling the core of ambient air particles. After intranasal booster immunizations with OVA, serum levels of OVA-specific IgE antibodies, and also markers of airway inflammation and cellular responses in the lung-draining mediastinal lymph nodes (MLN), were determined. PSP of all sizes promoted allergic responses, measured as increased serum concentrations of OVA-specific IgE antibodies. Further, PSP produced eosinophilic airway inflammation and elevated MLN cell numbers as well as numerically reducing the percentage of regulatory T cells. Ultrafine PSP produced stronger allergic responses to OVA than fine and coarse PSP. Although PSP enhanced sensitization in both female and male mice, significantly higher IgE levels and numbers of eosinophils were observed in females than males. However, the allergy-promoting effect of PSP was apparently independent of gender. Thus, our data support the notion that ambient air particle pollution may affect development of allergy in both female and male individuals.

Transmaternal bisphenol A exposure accelerates diabetes type 1 development in NOD mice

Diabetes mellitus type 1 is an autoimmune disease with a genetic predisposition that is triggered by environmental factors during early life. Epidemiological studies show that bisphenol A (BPA), an endocrine disruptor, has been detected in about 90% of all analyzed human urine samples. In this study, BPA was found to increase the severity of insulitis and the incidence of diabetes in female non obese diabetic (NOD) mice offspring after transmaternal exposure through the dams' drinking water (0, 0.1, 1, and 10mg/l). Both the severity of insulitis in the pancreatic islets at 11 weeks of age and the diabetes prevalence at 20 weeks were significantly increased for female offspring in the highest exposure group compared to the control group. Increased numbers of apoptotic cells, a reduction in tissue resident macrophages and an increase in regulatory T cells were observed in islets prior to insulitis development in transmaternally exposed offspring. The detectable apoptotic cells were identified as mostly glucagon producing alpha-cells but also tissue resident macrophages and beta-cells. In the local (pancreatic) lymph node neither regulatory T cell nor NKT cell populations were affected by maternal BPA exposure. Maternal BPA exposure may have induced systemic immune changes in offspring, as evidenced by alterations in LPS- and ConA-induced cytokine secretion in splenocytes. In conclusion, transmaternal BPA exposure, in utero and through lactation, accelerated the spontaneous diabetes development in NOD mice. This acceleration appeared to be related to early life modulatory effects on the immune system, resulting in adverse effects later in life.

Suppression of allergen-specific IgE in offspring after preconceptional immunisation: maternal, paternal and genetic influences

Immunisation of female mice with the allergen ovalbumin (OVA) during pregnancy reduces the OVA-specific IgE response in adult offspring. To approach primary prevention strategies for allergy, we investigated to what extent genetic, paternal and maternal factors influence this suppressive effect on allergic sensitisation in offspring and investigated the possibility of pregestational immunisation. Maternal allergen immunisation reduced OVA-specific IgE levels in immunised offspring, even after maternal immunisation up to 8 weeks before conception without further allergen exposure. Immunisation of immunodeficient BALB/c severe combined immune deficiency (SCID) dams mated with wild type males did not lead to IgE suppression in offspring, indicating the importance of a functional maternal immune system. Immunisation of male mice before the relevant spermatogenesis did not cause antibody suppression in offspring. OVA-specific IgG1, presumably of maternal origin, was present in naïve offspring only from immunised dams and was associated with suppressed IgE responses after offspring immunisation. The IgE-suppressive effect of maternal immunisation was demonstrated in all three immunocompetent strains tested (NIH/OlaHsd, BALB/cA and C57BL/6 mice). In conclusion, suppression of allergen-specific IgE production in offspring could not be induced by paternal immunisation, and genetic factors were of minor importance. In contrast, we demonstrate the necessity of maternal factors, possibly allergen-specific IgG1, resulting from a functional adaptive immune response, for the IgE-suppressive effect in offspring. These maternal factors could be induced by immunisation of female mice even before conception.

Long-term bisphenol A exposure accelerates insulitis development in diabetes-prone NOD mice

Exposure to the endocrine disruptor (ED) bisphenol A (BPA) used in polycarbonate plastic and epoxy resins appears ubiquitous since BPA can be found in over 90% of analyzed urine samples from all age groups. There is a parallel occurrence of increased prevalence in type 1 diabetes mellitus (T1DM) and an increased exposure to EDs the last decades. T1DM is caused by insulin deficiency due to autoimmune destruction of insulin producing pancreatic beta cells and has been suggested to be induced by various environmental factors acting together with a genetic predisposition. The objective of the present study was to investigate the effect of BPA (0, 1 and 100 mg/l BPA in the drinking water) on T1DM development in nonobese diabetic (NOD) mice, spontaneously developing T1DM. Histological evaluation of pancreas from 12-weeks-old female mice revealed significantly increased insulitis in mice exposed to 1 mg/l BPA, while the insulitis was less severe at the higher BPA exposure. Serum glucose levels in the 1 mg/ml BPA group tended to be hyperglycaemic, also indicating an accelerated onset of T1DM. The high BPA exposure seemed to counteract the diabetes development in females and also in male NOD mice for both BPA concentrations. Prior to insulitis, both BPA concentrations resulted in increased apoptosis and reduced numbers of tissue resident macrophages in pancreatic islets. In conclusion, long-term BPA exposure at a dose three times higher than the tolerable daily intake of 50 µg/kg, appeared to accelerate spontaneous insulitis and diabetes development in NOD mice.

Prenatal exposure to polychlorinated biphenyls and dioxins from the maternal diet may be associated with immunosuppressive effects that persist into early childhood

We investigated whether prenatal exposure from the maternal diet to the toxicants polychlorinated biphenyls (PCBs) and dioxins is associated with the development of immune-related diseases in childhood. Children participating in BraMat, a sub-cohort of the Norwegian Mother and Child Cohort Study (MoBa), were followed in the three first years of life using annual questionnaires (0-3years; n=162, 2-3years; n=180), and blood parameters were examined at three years of age (n=114). The maternal intake of the toxicants was calculated using a validated food frequency questionnaire from MoBa. Maternal exposure to PCBs and dioxins was found to be associated with an increased risk of wheeze and more frequent upper respiratory tract infections. Furthermore, maternal exposure to PCBs and dioxins was found to be associated with reduced antibody response to a measles vaccine. No associations were found between prenatal exposure and immunophenotype data, allergic sensitization and vaccine-induced antibody responses other than measles. Our results suggest that prenatal dietary exposure to PCBs and dioxins may increase the risk of wheeze and the susceptibility to infectious diseases in early childhood.

Toxicogenomic profiles in relation to maternal immunotoxic exposure and immune functionality in newborns

A crucial period for the development of the immune system occurs in utero. This results in a high fetal vulnerability to immunotoxic exposure, and indeed, immunotoxic effects have been reported, demonstrating negative effects on immune-related health outcomes and immune functionality. Within the NewGeneris cohort BraMat, a subcohort of the Norwegian Mother and Child Cohort Study (MoBa), immunotoxicity was demonstrated for polychlorinated biphenyls and dioxins, showing associations between estimated maternal intake levels and reduced measles vaccination responses in the offspring at the age of 3. The present study aimed to investigate this link at the transcriptomic level within the same BraMat cohort. To this end, whole-genome gene expression in cord blood was investigated and found to be associated with maternal Food Frequency Questionnaires-derived exposure estimates and with vaccination responses in children at 3 years of age. Because the literature reports gender specificity in the innate, humoral, and cell-mediated responses to viral vaccines, separate analysis for males and females was conducted. Separate gene sets for male and female neonates were identified, comprising genes significantly correlating with both 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and polychlorinated biphenyls (PCB) exposure and with measles vaccination response. Noteworthy, genes correlating negatively with exposure in general show positive correlations with antibody levels and vice versa. For both sexes, these included immune-related genes, suggesting immunosuppressive effects of maternal exposure to TCDD and PCB at the transcriptomic level in neonates in relation to measles vaccination response 3 years later.

Nitrogen dioxide: no influence on allergic sensitization in an intranasal mouse model with ovalbumin and diesel exhaust particles

The role of traffic-related air pollution in the development of allergic diseases is still unclear. We therefore investigated if NO₂, an important constituent of traffic-related air pollution, promotes allergic sensitization to the allergen ovalbumin (OVA). We also examined if NO₂ influenced the allergy adjuvant activity of diesel exhaust particles (DEP). For this purpose, mice were exposed intranasally to OVA with or without DEP present, immediately followed by exposure to NO₂ (5 or 25 parts per million [ppm]) or room air for 4 h in whole body exposure chambers. Eighteen hours after the last of three exposures, the lungs of half of the animals were lavaged with saline and markers of lung damage and lung inflammation in the bronchoalveolar lavage fluid (BALF) were measured. Three weeks later, after intranasal booster immunizations with OVA, the levels of OVA-specific IgE and IgG2a antibodies in serum were determined. Both NO₂ (25 ppm) and DEP gave lung damage, measured as increased total protein concentration in BALF, whereas only NO₂ seemed to stimulate release of the proinflammatory cytokine tumor necrosis factor alpha (TNF-α). In contrast, only DEP significantly increased the number of neutrophils. Furthermore, DEP in combination with OVA stimulated the production of serum allergen-specific IgE antibodies. NO₂, however, neither increased the production of allergen-specific IgE antibodies, nor influenced the IgE adjuvant activity of DEP. Thus, based on our findings, NO₂ seems to be of less importance than combustion particles in the development of allergic diseases after exposure to traffic-related air pollution.

Determinants of experimental allergic responses: interactions between allergen dose, sex and age

The prevalence of allergic diseases is influenced by sex and age. Although mouse models are widely used in allergy research, few experimental studies have examined the interaction effects of sex and age on allergy outcomes. Our aim was to investigate the individual and combined effects of sex and age on allergic sensitization and inflammation in two mouse models: an intraperitoneal (i.p.) and an intranasal (i.n.) sensitization model. We also investigated how the allergen immunization dose interacted with age and sex in the i.p. model. Female and male mice were immunized i.p. or i.n. with ovalbumin when 1, 6 or 20 weeks old. In both models, allergen challenges were performed by i.n. delivery. Serum antibodies, draining lymph node cytokine release and airway inflammatory responses were assessed. In the i.p. model, the antibody and cytokine levels and airway inflammation were highly influenced by immunization dose and age. The responses increased with age when using a low immunization dose, but decreased with age when using a high immunization dose. In the i.n. model, antibody production and airway tissue inflammation increased with age. Female compared with male mice generally developed more pronounced antibody and inflammatory responses. Relative to older mice, juvenile mice had augmented airway inflammation to allergen exposures. The study demonstrates that immunization dose, sex and age are highly influential on allergy outcomes. To better mimic different life stages of human allergic airway disease, murine models, therefore, require careful optimization.

Prenatal exposure to polychlorinated biphenyls and dioxins is associated with increased risk of wheeze and infections in infants

The birth cohort BraMat (n = 205; a sub-cohort of the Norwegian Mother and Child Cohort Study (MoBa) conducted by the Norwegian Institute of Public Health) was established to study whether prenatal exposure to toxicants from the maternal diet affects immunological health outcomes in children. We here report on the environmental pollutants polychlorinated biphenyls (PCBs) and dioxins, as well as acrylamide generated in food during heat treatment. The frequency of common infections, eczema or itchiness, and periods of more than 10 days of dry cough, chest tightness or wheeze (called wheeze) in the children during the first year of life was assessed by questionnaire data (n = 195). Prenatal dietary exposure to the toxicants was estimated using a validated food frequency questionnaire from MoBa. Prenatal exposure to PCBs and dioxins was found to be associated with increased risk of wheeze and exanthema subitum, and also with increased frequency of upper respiratory tract infections. We found no associations between prenatal exposure to acrylamide and the health outcomes investigated. Our results suggest that prenatal dietary exposure to dioxins and PCBs may increase the risk of wheeze and infectious diseases during the first year of life.

In vitro cytokine release from human peripheral blood mononuclear cells in the assessment of the immunotoxic potential of chemicals

Alternative methods to the use of animals in testing of chemicals are needed. We investigated if the immunotoxic potential of 12 dietary toxicants could be predicted from effects on cytokine release from human peripheral blood mononuclear cells (PBMC) after in vitro exposure. Nine cytokines were selected to reflect different types of immune responses. The toxicants were classified as immunotoxic or non-immunotoxic substances according to the published in vivo data. Isolated human PBMC were exposed for 20 h to three concentrations of each of the 12 substances in the presence of human liver S9 fraction. After further incubation of PBMC in fresh medium containing the mitogen phytohemagglutinin (PHA, 10 μg/ml) for 48 h, release of the nine selected cytokines into the supernatant as well as cell proliferation were measured by Luminex technology™ and the BrdU incorporation assay, respectively. All 12 substances investigated affected the release of one or more cytokines, and each of the substances showed different cytokine release patterns. Within the limitations of the study design, the present study suggests that the effect of the substances on mitogen-induced cytokine release from PBMC cannot predict their immunotoxic potential, but may be useful in mechanistic studies.

Particles from wood smoke and road traffic differently affect the innate immune system of the lung

The effect of particles from road traffic and wood smoke on the innate immune response in the lung was studied in a lung challenge model with the intracellular bacterium Listeria monocytogenes. Female Balb/cA mice were instilled intratracheally with wood smoke particles, particles from road traffic collected during winter (studded tires used; St+), and during autumn (no studded tires; St-), or diesel exhaust particles (DEP). Simultaneously with, and 1 or 7 days after particle instillation, 10(5) bacteria were inoculated intratracheally. Bacterial numbers in the lungs and spleen 1 day after Listeria challenge were determined, as an indicator of cellular activation. In separate experiments, bronchoalveolar lavage (BAL) fluid was collected 4 h and 24 h after particle instillation. All particles tested reduced the numbers of bacteria in the lung 24 h after bacterial inoculation. When particles were given simultaneously with Listeria, the reduction was greatest for DEP, followed by St+ and St-, and least for wood smoke particles. Particle effects were no longer apparent after 7 days. Neutrophil numbers in BAL fluid were increased for all particle exposed groups. St+ and St- induced the highest levels of IL-1beta, MIP-2, MCP-1, and TNF-alpha, followed by DEP, which induced no TNF-alpha. In contrast, wood smoke particles only increased lactate dehydrogenase (LDH) activity, indicating a cytotoxic effect of these particles. In conclusion, all particles tested activated the innate immune system as determined with Listeria. However, differences in kinetics of anti-Listeria activity and levels of proinflammatory mediators point to cellular activation by different mechanisms.

Particle size determines activation of the innate immune system in the lung

Our knowledge about particle size in relation to activation of the innate immune system is limited. Therefore, the acute effect of particle exposure on the innate immune system was studied in a lung model using the intracellular bacterium Listeria monocytogenes. Female Balb/cA mice were instilled intratracheally with polystyrene particles (PSP) of different diameters (0.064, 0.202, 1.053 and 4.646 mum) simultaneously with or 1 day prior to inoculation of 10(5) bacteria. Mice were sacrificed 1 day after Listeria challenge, and the numbers of viable bacteria in the lungs and the spleen were determined as a measure of cellular activation. In separate experiments, bronchoalveolar lavage (BAL) fluid was collected. Only mice exposed to the smallest PSP (0.064 and 0.202 mum) had significantly reduced bacterial numbers in the lung after particles and Listeria were given simultaneously. When particles were given 1 day prior to Listeria challenge also the largest 4.646 mum PSP, but not the medium size 1.053 mum PSP, reduced bacterial numbers. The number of neutrophils in BAL fluid was increased for all PSP-exposed groups after 24 h, and tended to be highest in the group exposed to 4.646 mum PSP. TNF-alpha, IL-1beta and MIP-2 were significantly increased in BAL fluid after exposure to the largest compared with the smallest PSP. In conclusion, activation of the innate immune system by chemical-free particles was size-dependent. Ultrafine and coarse particles appeared to activate cells by different mechanisms, which implies qualitative differences between the health effects of ambient air particulate matter size fractions.

Allergy adjuvant effect of particles from wood smoke and road traffic

There is growing evidence that in addition to augmenting the severity of asthma and allergic diseases, particulate air pollution also increases the incidence of allergy and asthma. We studied the adjuvant effect of particles from wood smoke and road traffic on the immune response to the allergen ovalbumin (OVA). OVA with and without particles was injected into one hind footpad of Balb/cA mice. All particles together with OVA significantly increased the level of OVA-specific immunoglobulin E (IgE) in serum, compared to groups given OVA or particles alone. Reference diesel exhaust particles (DEP) with OVA induced the highest levels of IgE, whereas no clear difference was observed between particles from road traffic and wood smoke. Road traffic particles collected in the autumn induced higher IgE values with OVA than corresponding particles collected during the winter season when studded tires are used, suggesting that studded tire-generated road pavement particles have less allergy adjuvant activity than exhaust particles. Compared to OVA or particles alone, all particles with OVA increased popliteal lymph node cell numbers, cell proliferation, ex vivo secretion of IL-4 and IL-10 after ConA stimulation, and the expression of several cell surface molecules (CD19, MHC class II, CD86 and CD23). Wood smoke particles with OVA induced somewhat higher cellular responses than road traffic particles, but less than DEP with OVA which seemed to be the most potent particle in inducing cellular as well as antibody responses. Thus, wood smoke particles had about the same capacity to enhance allergic sensitization as road traffic particles, but less than diesel exhaust particles.

Quantification and characterisation of IgG binding to mould spores by flow cytometry and scanning electron microscopy

The concentration of mould-specific IgG antibodies in serum may objectively indicate mould exposure and can help identifying exposed individuals. Although inhaled spores probably are the most important source of mould exposure, the commonly used methods for detecting mould-specific IgG antibodies are based on extracts from all mould components, with only low contribution from spores. We have developed a flow cytometric method using surface antigens on mould spores for quantifying mould-specific IgG antibodies in serum. Flow cytometric results were evaluated by comparison with ImmunoCap and ELISA measurements. The flow cytometric assay showed a broad linear dose-dependency and correlated moderately to strongly (r=0.41-0.97) with ImmunoCap and ELISA measurements. The IgG antibody binding was studied in detail by immunolabelling in scanning electron microscopy (SEM), revealing that morphology and IgG antibody binding differed among spores, both within and between mould strains. Germination studies by flow cytometry and SEM showed that IgG antibody binding to mould spores was altered during germination due to loss of coat. The present spore based antibody assay are simple and suitable for quantification of mould-specific IgG antibodies in serum, and includes specificity to other and possibly more relevant antigens than existing methods.

Popliteal lymph node (PLN) assay to study adjuvant effects on respiratory allergy

Different variants of the popliteal lymph node (PLN) assay have been published. Here we describe the adjuvant popliteal lymph node assay, an immune response assay to study the adjuvant activity of soluble substances as well as particulate matter. The substance to be studied for adjuvant activity is injected into the hind footpad of mice or rats together with an antigen. Adjuvant activity is determined as the increase in PLN weight and cell numbers in animals receiving antigen together with the substance under study, compared with PLN weight and cell numbers in animals given the antigen without the substance in question, and animals given the putative adjuvant alone. Because lymph node weight and cell numbers are immunologically non-specific parameters, specific immune response assays like serum antibody responses or antibody-forming cell numbers should additionally be performed. Different antigens and immune response assays may be used, depending on the research question asked. In relation to respiratory (or food) allergy, the assays should as a minimum include determination of specific IgE in serum, and preferably also IgG1 (mouse). Serum specific IgG2a antibody determination may be added to get an indication of the Th1-Th2-balance of the response. The adjuvant PLN assay, with cellular response assays performed in the draining popliteal lymph node and antibody determinations in serum, requires small amounts of test material. The assay offers a practical, sensitive and reproducible method to determine the adjuvant activity of soluble substances as well as particulate material, with the possibility to also perform mechanistic studies.

The allergy adjuvant effect of particles - genetic factors influence antibody and cytokine responses

BACKGROUND

There is increasing epidemiological and experimental evidence for an aggravating effect of particulate air pollution on asthma and allergic symptoms and, to a lesser extent, on allergic sensitization. Genetic factors appear to influence not only the magnitude, but also the quality of the adjuvant effect of particles with respect to allergen-specific IgE (Th2-associated) and IgG2a (Th1-associated) responses. In the present study, we aimed to investigate how the genetic background influences the responses to the allergen and particles alone and in combination. We examined how polystyrene particles (PSP) affected the IgE and IgG2a responses against the model allergen ovalbumin (OVA), after subcutaneous injection into the footpad of BALB/cA, BALB/cJ, NIH and C3H/HeN mice, Further, ex vivo IL-4, IFN-gamma and IL-10 cytokine secretion by Con A-stimulated cells from the draining popliteal lymph node (PLN) five days after injection of OVA and PSP separately or in combination was determined.

RESULTS

PSP injected with OVA increased the levels of OVA-specific IgE antibodies in all strains examined. In contrast, the IgG2a levels were significantly increased only in NIH and C3H/HeN mice. PSP in the presence of OVA increased cell numbers and IL-4, IL-10 and IFN-gamma levels in BALB/cA, NIH and C3H/HeN mice, with the exception of IFN-gamma in NIH mice. However, each mouse strain had their unique pattern of response to OVA+PSP, OVA and PSP, and also their unique background cytokine response (i.e. the cytokine response in cells from mice injected with buffer only).

CONCLUSION

Genetic factors (i.e. the strain of mice) influenced the susceptibility to the adjuvant effect of PSP on both secondary antibody responses and primary cellular responses in the lymph node, as well as the cellular responses to both OVA and PSP given separately. Interestingly, PSP alone induced cytokine responses in the lymph node in some of the mouse strains. Furthermore, we found that the ex vivo cytokine patterns did not predict the in vivo Th2- and Th1-associated antibody response patterns in the different mouse strains. The results indicate that insoluble particles act by increasing the inherent response to the allergen, and that the genetic background may determine whether an additional Th1-associated component is added to the response.

The IgE adjuvant effect of particles: characterisation of the primary cellular response in the draining lymph node

Diesel exhaust particles, and polystyrene particles (PSP) as a model for the insoluble particle core, have an adjuvant effect on allergen-specific IgE production in mice. We therefore examined the primary immune response in the draining popliteal lymph node (PLN) to the allergen ovalbumin (OVA) injected together with polystyrene particles into the footpad of BALB/cA mice. Similar numbers of particle-containing cells were observed in the draining lymph node on day 1 after injection of PSP alone or OVA + PSP, the numbers increasing continuously until day 21. The total lymph node cell numbers increased three to four times in the OVA + PSP group compared to both OVA and PSP groups, peaking on day 5. The increase in B cell numbers was twice the increase in T cell numbers. On day 5, OVA + PSP increased the expression of most surface markers measured (MHC class II, CD86, CD23, CD69) compared to OVA and PSP. Further, the ex vivo production of IL-4 and IL-10 by PLN cells from OVA + PSP-injected animals was increased. In conclusion, whereas PSP alone did not influence any of the immunologic markers studied, the adjuvant effect of PSP on the IgE antibody response to OVA was associated with an early increased primary cellular response in the draining lymph node.

Ambient air particles from four European cities increase the primary cellular response to allergen in the draining lymph node

In the RAIAP (respiratory allergy and inflammation due to ambient particles) project, qualitative properties of ambient air particles from Amsterdam, Oslo, Lodz and Rome were investigated in relation to inflammation and allergy. Most collected particle fractions were found to increase the allergen-specific IgE and IgG2a responses after subcutaneous injection of particles with allergen in mice. However, some fractions appeared to skew the antibody response towards more Th1- or Th2-associated antibody isotypes, and the fine fractions were found to be more potent than the coarse fractions with regard to IgE adjuvant activity. In the present study we investigated the cellular response in the draining lymph node 5 days after a subcutaneous injection of selected RAIAP particle fractions. The particles (100 microg) were injected into both hind footpads of BALB/cA mice, in the presence or absence of the allergen ovalbumin (OVA, 50 microg). We also studied if the coarse and fine RAIAP particle fractions affected the cellular responses to OVA differently. The number of lymph node cells, as well as the relative number of B and T lymphocytes and T helper cells were determined. Expression of cell surface molecules (MHC class II, CD86 and CD23) and ex vivo cytokine production (IL-4, IL-10 and IFN-gamma) by the lymph node cells were measured. Overall, particles in the presence of allergen enhanced the levels of the various cellular parameters compared to allergen alone or particles alone. In the absence of allergen, ambient air particles, in contrast to diesel exhaust particles, marginally affected some cellular parameters. By histological examination of the lymph node, the particles appeared to be scattered between the lymphocytes, often localised within macrophage-like (acid phosphatase positive) cells. The cell parameters measured could, for the individual sample, neither predict the degree of a Th2- or Th1-skewed antibody response, nor the stronger antibody adjuvant capacity of the fine than the coarse particle fractions. In conclusion, we have shown that coarse and fine ambient air particles from different European cities enhance the cellular response in the draining lymph node after injection with an allergen. In the absence of allergen, ambient particles only marginally affected the cellular parameters.

The Capacity of Particles to Increase Allergic Sensitization Is Predicted by Particle Number and Surface Area, Not by Particle Mass

Particle exposure has traditionally been monitored as mass concentration of PM10 (particles with an aerodynamic diameter less than 10 microm), more recently also as PM2.5. The mass concentration is strongly influenced by the large particles. Therefore, particle mass is a poor measure for characterizing the amount of the small, possibly more biologically potent particles. We used polystyrene particles (PSP) ranging in diameter from 0.0588 to 11.14 microm, carbon black (CB), and diesel exhaust particles (DEP), to study the adjuvant effect of particles on the immune response to the allergen ovalbumin (OVA) after sc injection into the footpad of BALB/cA mice. At a given mass dose, the small particles (0.0588 and 0.202 microm PSP, CB, and DEP) increased the allergen-specific IgE serum levels to a substantially higher degree than the larger particles (1.053, 4.64, and 11.14 microm PSP). Further, in the draining lymph node during the primary response, the fine particles (0.202 microm) with OVA increased cell numbers, expression of surface markers (CD19, MHC class II, CD86, and CD23) and ex vivo production of IL-4 and IL-10, whereas the largest (11.14 microm) particles did not. Linear regression analyses indicated that the IgE response was not predicted by particle mass (R2 = 0.06), but was predicted by the total particle surface area (R2 = 0.64), number of particles (R2 = 0.62), and particle diameter (R2 = 0.58). In conclusion, we found that fine particles exerted stronger adjuvant effects on allergic responses than larger particles at equal mass doses. Consequently, the dose described as total particle surface area or particle number predicts the adjuvant effect of particles better than the currently used particle mass.

Blood and spleen lymphocytes as targets for immunotoxic effects in the rat--a comparison

Traditionally, immunotoxicological studies in the rat have been performed by measuring the effect of chemical substances on spleen lymphocytes in vivo and in vitro. However, rat blood lymphocytes may be more relevant than spleen cells for comparison with human blood lymphocytes. Further, lymphocytes in blood may be a more sensitive indicator of immunotoxic effects than spleen lymphocytes. Finally, in longitudinal studies peripheral blood specimens can be collected repeatedly from the same animals, thereby reducing the number of animals sacrificed and, possibly, experimental variation. We compared blood and spleen lymphocyte parameters in rats treated with a single dose of the immunosuppressant cyclophosphamide (CY), monitoring effects on blood and spleen lymphocytes by immunophenotyping. We also performed repeated bleedings to demonstrate the feasibility of following the time course of induced changes in the same animals. Immunophenotyping as well as total mononuclear cell counts consistently showed as large or lager effects of CY in blood lymphocytes than in spleen cells. Further, the measured effects in blood lymphocytes became statistically significant at an earlier time point, compared to spleen cells. Repeated bleedings of the same animals illustrated that blood specimens drawn from a peripheral vein give sufficient numbers of cells to perform immunotoxicological tests.