Enhanced human IgE production results from exposure to the aromatic hydrocarbons from diesel exhaust: direct effects on B-cell IgE production

Diesel exhaust particulates upregulate histamine receptor mRNA and increase histamine-induced IL-8 and GM-CSF production in nasal epithelial cells and endothelial cells

BACKGROUND

Histamine is the most important chemical mediator in the pathogenesis of nasal allergy. Diesel exhaust particulates (DEPs) are common air pollutants from diesel engine-powered car exhaust and cause chronic airway diseases. Recently we observed that the nasal reactivity to histamine was enhanced in diesel exhaust-exposed guinea-pigs. It was also revealed that epithelial cells and endothelial cells in the airway produce certain cytokines in response to histamine.

OBJECTIVE

We examined the effects of DEP extract on the expression of histamine H1 receptor (H1R) mRNA in human nasal epithelial cells (HNECs) and human mucosal microvascular endothelial cells (HMMECs), and on the production of IL-8 and GM-CSF induced by histamine.

METHODS

HNECs and HMMECs were isolated from human nasal mucosa specimens. HNEC and HMMEC monolayers were cultured in the presence or absence of DEP extract. The change in the expression of H1R mRNA was then evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR) and the Southern blot analysis. To investigate the effects of DEP extract on the histamine-induced cytokine production, HNEC and HMMEC monolayers were cultured in the presence or absence of DEP extract for 3-24 h. After three washes with PBS, they were then incubated with 10(-6) mol/L histamine for 24 h. The amounts of IL-8 and GM-CSF in the culture media were measured by enzyme-linked immunoabsorbent assay.

RESULTS

DEP extract increased the expression of H1R mRNA in both HNECs and HMMECs. The amount of IL-8 and GM-CSF, induced by histamine, was significantly higher in DEP extract pretreated HNECs and HMMECs than nontreated HNECs and HMMECs.

CONCLUSION

These results strongly suggest that DEP accelerates the inflammatory change by not only directly upregulating H1R expression but also increasing histamine-induced IL-8 and GM-CSF production.

Early IL-4 production driving Th2 differentiation in a human in vivo allergic model is mast cell derived

IL-4 is central to the formation of IgE and the development of Th2 effector cells, both key features of an allergic response. We have examined IL-4 production early in the formation of an allergic response by using a previously established human in vivo model of allergic rhinitis where allergic subjects are challenged internasally with allergen and the particulate pollutant diesel exhaust particles (DEP). This model is characterized by enhanced IgE production and deviation to a Th2-type cytokine profile in nasal lavage fluid from these subjects. In this model, IL-4 protein and IL-4-positive cells could first be detected 4 h after challenge and maximal production was observed after 18 h. Two-color flow cytometric analysis for the detection of intracellular IL-4 and surface markers was performed on nasal cells recovered 4 h after challenge. At this time, CD117(+) (c-kit+) cells constituted between 65 and 100% of the IL-4(+) cells, while 0-12% of the IL-4(+) cells were CD3 positive. No IL-4(+) CD19/CD20(+) or IL-4(+) CD56(+) cells were detected at 4 h. As the allergic response progressed the primary source of IL-4 changed. At the peak of IL-4 production, 18 h after challenge, CD3(+) comprised the majority of cells staining for intracellular IL-4 (73 to 100%). Thus we show an initial role for cells of the mast cell/basophil lineage residing in the nasal mucosa in the initial production of IL-4, which frames the subsequent immune response by expanding the repertoire of TH2 cytokine-producing cells in the local microvicinity.

Combined nasal challenge with diesel exhaust particles and allergen induces In vivo IgE isotype switching

In this study we undertook to provide evidence for local in vivo isotype switching to IgE following nasal challenges. Detection of deleted switch circular DNA (switch circles) by a novel nested polymerase chain reaction-based approach was employed as definitive molecular evidence of Ig isotype switching. Nasal challenge in humans with diesel exhaust particles (DEP) plus ragweed antigen has been shown to enhance local IgE production, stimulate local cytokine production, and markedly increase mucosal IgE antibody to ragweed. Four days after combined intranasal DEP plus ragweed challenge, we detected and characterized clones of deleted switch circular DNA (Sepsilon /Smu) representing switching from mu to epsilon from nasal lavage cells. No switch circular DNA was detected in nasal lavage cells following challenge with DEP alone nor with ragweed allergen alone. These results indicate that the combination of mucosal stimulation with DEP and ragweed allergen is capable of driving in vivo isotype switching to IgE in humans with ragweed allergy. These results are the first direct demonstration of in vivo IgE isotype switching in humans.

Human IgE production in hu-PBL-SCID mice injected with birch pollen and diesel exhaust particles

Mice with severe combined immunodeficiency were transplanted with human peripheral blood lymphocytes (hu-PBL-SCID mice). The response to immunisation with birch pollen was used to study possible effects of diesel exhaust particles (DEP) and aluminium hydroxide (Al(OH)3) on human IgE production in this human in vivo model. The adjuvants were well tolerated, as determined by the number of human cells in the peritoneal cavity at the end of the experiments. Total and birch pollen-specific IgE was detected in 76 and 41% of the mice, respectively. In the present experiments where the mice were stimulated early with birch pollen, a doubling in percentage of hu-PBL-SCID mice with production of specific IgE was observed, as compared to later stimulation used in previous experiments. Although a tendency to higher total IgE levels was observed after treatment with DEP, no statistically significant adjuvant effect of DEP or Al(OH)3 could be demonstrated. Electron microscopy analysis after immunogold labelling showed that the major birch pollen allergen Bet v I was released from the pollen grains and adsorbed to the surface of the DEP. Early stimulation with allergen appears to be important for optimal production of specific IgE in the hu-PBL-SCID model. However, our results show that further improvements are needed in order to demonstrate the expected effects from adjuvants and environmental pollutants.

Macrophage Activation by Polycyclic Aromatic Hydrocarbons: Evidence for the Involvement of Stress-Activated Protein Kinases, Activator Protein-1, and Antioxidant Response Elements

Polycyclic aromatic hydrocarbons (PAH) contained in fossil fuel combustion particles enhance the allergic response to common environmental Ags. A key question is: what are molecular pathways in the immune system by which PAH and conversion products drive allergic inflammation? Circumstantial evidence suggests that macrophages are involved in PAH-induced responses. We demonstrate that a representative PAH, β-napthoflavone (BNF), and a representative quinone metabolite, tert-butylhydroxyquinone (tBHQ), induce Jun kinase and p38 mitogen-activated protein kinase activities in parallel with the generation of activator protein-1 (AP-1) mobility shift complexes in THP-1 and RAW264.7 macrophage cell lines. Activation of mitogen-activated protein kinases was dependent on generation of oxidative stress, and could be inhibited by N-acetylcysteine. Another genetic response pathway linked to PAH is the antioxidant response element (ARE), which regulates expression of detoxifying enzymes. BNF and tBHQ activated a human ARE (hARE) reporter gene in RAW264.7 cells. Interestingly, bacterial lipopolysaccharide also induced hARE/chloramphenicol acetyltransferase activity. While the hARE core, GTGACTCAGC, contains a consensus AP-1 sequence (underlined), AP-1 was not required for hARE activation. This suggests that PAH and their conversion products operate via ARE-specific transcription factors in the immune system. BNF and tBHQ did, however, induce AP-1 binding to the hARE, while constitutively active Jun kinase interfered in hARE/chloramphenicol acetyltransferase activation. This suggests that AP-1 proteins negatively regulate the hARE. These data establish important activation pathways for PAH in the immune system and provide us with targets to modulate the effect of environmental pollutants on allergic inflammation.

Diesel exhaust enhances allergic airway inflammation and hyperresponsiveness in mice

We previously reported that the intratracheal instillation of diesel exhaust particles enhances allergic airway inflammation and hyperresponsiveness in mice. However, it is not known whether the effects of such instillation differ from those obtained with the daily inhalation of diesel exhaust. We therefore examined whether the inhalation of diesel exhaust would also enhance allergic reactions. Mice were exposed to diesel exhaust or clean air for 5 wk. After the first week, the animals were sensitized to ovalbumin by intraperitoneal injection. At the end of the exposure period, they underwent an ovalbumin challenge. Control animals received saline instead of ovalbumin. Independently of ovalbumin sensitization, diesel exhaust caused an increase in the numbers of neutrophils and macrophages in bronchoalveolar lavage fluid, whereas a significant increase in eosinophil numbers occurred only after antigen challenge combined with diesel exhaust exposure. Furthermore, ovalbumin alone caused an increase in eosinophil numbers in lung tissue, and this was enhanced by diesel exhaust. Exposure to diesel exhaust combined with ovalbumin sensitization, but not diesel exhaust inhalation alone, enhanced the number of goblet cells in lung tissue, respiratory resistance, production of ovalbumin-specific immunoglobulin E and G1 in the serum, and expression of interleukin-5 in lung tissue.

Allergic and immunologic profile of symptomatic Persian Gulf War veterans

BACKGROUND

Persian Gulf War veterans have been enrolled in the Veterans Administration Persian Gulf Health Registry for evaluation of unexplained symptoms and illnesses. The allergy and immunology division at the West Los Angeles Veterans Administration Medical Center evaluated 20 consecutive symptomatic Persian Gulf War veterans.

OBJECTIVE

The purpose of this study was to examine the immunologic profiles of symptomatic Persian Gulf War Veterans.

METHODS

A detailed history was obtained that included duties/responsibilities, length of time in the Persian Gulf, location, and exposures during the Gulf War. A complete physical examination was performed, with extensive laboratory testing and immediate and delayed hypersensitivity skin testing. Data from these Persian Gulf War Veterans were compared with a control population consisting of 44 non-Persian Gulf War veterans enrolled in our allergy and immunology clinic. Presenting allergic symptoms, presence of atopy, and total serum IgE levels were compared.

RESULTS

Persian Gulf study patients and registry patients had a broad spectrum of nonspecific symptoms as compared with allergy clinic control patients who had dermatologic and respiratory symptoms. Persian Gulf study patients with allergy symptoms had a higher mean IgE level (88.7 IU/mL) than Persian Gulf study patients without allergy symptoms (47.5 IU/mL). Persian Gulf study patients with positive skin tests had a higher mean IgE level (161.5 IU/mL) than Persian Gulf study patients with negative skin tests (22.3 IU/mL). Laboratory data showed no significant immune abnormalities.

CONCLUSION

Our study showed that 20 Persian Gulf veterans with a multitude of nonspecific symptoms had no immune abnormality. Mean IgE levels and eosinophil counts correlated with atopic state and reported allergy symptoms.

Diesel exhaust particles induced release of interleukin 6 and 8 by (primed) human bronchial epithelial cells (BEAS 2B) in vitro

Several epidemiological studies have recently shown associations of increased premature mortality rates with ambient particulate air pollution. Diesel exhaust particles (DEP) may constitute an important part of (ultra)fine particulate air pollution in urban areas and may therefore contribute to its toxicity. Epithelial lining of the respiratory tract may be the first target of the toxic effects of DEP, that upon exposure may release pro-inflammatory mediators such as interleukin 6 and 8 (IL-6, IL-8), ultimately causing airway tissue damage and immune alterations. In this study the effects of in vitro DEP exposure (0.04-0.33 mg/mL) on IL-6, IL-8 production by a human bronchial epithelial cell line (BEAS-2B) were investigated. For comparison, the production of interleukins during exposure to silica and titanium oxide (TiO2) were also studied, representing relatively toxic and non-toxic particles, respectively. Scanning and transmission electron microscopy showed that the size of the DEP particles ranged between 25 to 35 nm and that DEP was phagocytized by BEAS-2B cells. An increase in IL-6 and IL-8 production (11- and 4-fold, respectively) was found after 24 or 48 h of exposure to DEP compared to the non-exposed cells. This increase was lower compared to silica (17- and 3.3-fold) and higher as compared to TiO2 which showed no increase for IL-6 and IL-8. To study the DEP effect on inflammation-primed cells, BEAS-2B cells were exposed to both tumor necrosis factor-alpha (TNF-alpha) and subsequently to DEP. Exposure to TNF-alpha caused a strong increase in IL-6 and IL-8 production. Additive effects on the IL-6 and IL-8 production by BEAS-2B cells were found after TNF-alpha priming and subsequently exposure to DEP, only at a low dose of DEP and TNF-alpha (0.05-0.2 ng/mL). In conclusion, BEAS-2B phagocytized DEP and produced an increased amount of IL-6 and IL-8. In TNF-alpha primed BEAS-2B cells, DEP increased interleukin production only at low concentrations of DEP and TNF-alpha. Whether this increased production of pro-inflammatory interleukins affects vulnerable balances in the immune system, such as T help-1 and T help-2 subsets ratios, resulting in an altered resistance to respiratory tract infections or altering the expression of respiratory allergy, is the subject of further studies.

The adjuvant activity of diesel exhaust particles and carbon black on systemic IgE production to ovalbumin in mice after intranasal instillation

The adjuvant activity of diesel exhaust particles (DEP) on systemic IgE production to ovalbumin (OA) was studied in mice after intranasal administration. The main purpose was to elucidate which part of the particles was responsible for the effect, the carbon core and/or the adsorbed organic substances. Female Balb/cA mice were immunized with OA either alone or in combination with DEP or carbon black particles (CB), the latter used as a surrogate for the non-extractable carbon core of DEP. Controls were given DEP, CB or buffer alone. The animals were immunized four times. 1 and 2 weeks after the last immunization anti OA IgE antibody in serum was analysed by enzyme linked immunosorbent assay (ELISA). An increased response to the antigen was observed in animals receiving OA together with DEP or CB, compared with animals receiving OA alone. The increased response was seen as both increased number of responding animals and increased serum anti OA IgE antibody. For OA + DEP 37% of the animals showed a serum anti OA IgE response, whereas 22% of the OA + CB animals and 10% of the OA animals responded. In conclusion, this work shows that not only DEP, but also CB have an adjuvant activity for specific IgE production after intranasal instillation. However, the activity of DEP may be more pronounced than that of CB. The results imply that both the organic matter adsorbed to DEP and the non-extractable carbon core are responsible for the observed adjuvant effect.

Mechanisms of gastrointestinal reactions to food

Much of the genetic information that modulates mucosal immune responses was encoded several million years ago and has subsequently been subjected to modifications selected by the impact of microorganisms and food antigens. Confronted with these challenges, the intestinal immune system has developed two arms: (1) immune exclusion performed mainly by secretory IgA antibodies to inhibit colonization of pathogenic microorganisms and penetration of harmful antigens; and (2) down-regulatory mechanisms to avoid local and peripheral overreaction (hypersensitivity) towards innocuous substances. The latter phenomenon is called oral tolerance and apparently explains why most individuals show no adverse immune reactions food. When the mucosal barrier function is insufficient, tolerance to dietary antigens is abrogated in genetically susceptible individuals. This is most likely to occur during the vulnerable period after birth before the immunoregulatory network has been established. Breast-feeding appears to be immunologically important during this period, not only to substitute for the infant's lacking secretory antibodies but also because of its immune-modulating effects.

Diesel exhaust particles and carbon black have adjuvant activity on the local lymph node response and systemic IgE production to ovalbumin

The possible adjuvant effect of diesel exhaust particles (DEP) on the response to the model allergen ovalbumin (OA) was studied in BALB/c mice using the popliteal lymph node (PLN) assay. In addition to changes in PLN weight, cell numbers and cell proliferation, specific serum IgE anti-OA antibody levels were measured. OA inoculated together with DEP into one hind footpad gave a significantly augmented response (increase in weight, cell numbers and cell proliferation) in the draining popliteal lymph node as compared to DEP or OA alone. Also, the local lymph node response was of longer duration when DEP were given with the allergen. Experiments in thymus-deficient nu/nu mice indicated that the lymph node response observed in BALB/c mice was of a specific immunologic character and not an unspecific inflammatory reaction. The OA-specific IgE response was increased in mice receiving OA together with DEP as compared to the response in mice receiving OA without DEP. Carbon black (CB) was given with and without OA in some experiments, as a surrogate for the non-extractable core of DEP. CB was found to resemble DEP in its capacity to increase the local lymph node response and serum specific IgE response to OA, but CB appeared to be slightly less potent than DEP. Thus, both DEP and CB had a significant adjuvant effect on the local immune-mediated inflammatory response and on the systemic specific IgE response to allergen. The results indicate that the non-extractable particle core contributes substantially to the adjuvant activity of DEP.

Modulation of T-helper cell populations: potential mechanisms of respiratory hypersensitivity and immune suppression

Information presented at this symposium indicates that modulation of Th cell responses is one means by which xenobiotics may cause immunotoxicity. A shift from Th1 to Th2 responses can enhance both infectious and allergic disease. Hence, in some cases, a common mechanism may be responsible for effects that are generally considered to be very different. Because cytokines produced in the inflammatory process play a role in modulation of Th cell responses, there is a mechanism by which agents that appear to have only local effects at the portal of entry may, in fact, affect immune responses systemically. An understanding of conditions which trigger certain cytokine responses may be useful not only in understanding inflammation but also in predicting certain kinds of immunosuppressive and allergic responses. Future studies in this area are likely to provide insights into many areas of immunotoxicology.

Effects of diesel exhaust particles on the release of interleukin-1 and tumor necrosis factor-alpha from rat alveolar macrophages

The effects of diesel exhaust particles (DEP) and their components (washed dust and methanol extracts) on the release of proinflammatory cytokines, interleukin-I (IL-1), and tumor necrosis factor-alpha (TNF-alpha) by alveolar macrophages (AM) were investigated. Rat AM were incubated with 0, 5, 10, 20, 50, or 100 micrograms/10(6) AM/mL of DEP, methanol-washed DEP, or equivalent concentrations of DEP methanol extracts at 37 degrees C for 24 h. AM-conditioned supernatants were collected and assayed for the activities of IL-1 and TNF-alpha. At high concentrations both DEP and DEP methanol extracts were shown to increase IL-I-like activity secreted by AM, whereas methanol-washed DEP had no effect. Neither DEP, methanol-washed DEP, nor DEP methanol extracts was found to stimulate the secretion of TNF-alpha. The effects of DEP on the release of IL-I and TNF-alpha by lipopolysaccharide (LPS)- or interferon-gamma (IFN-gamma)-primed AM were also studied. AM were preincubated with various concentrations of DEP for 2 h, then challenged with either 0.1 microgram/mL of LPS or 5 units/mL of IFN-gamma. DEP inhibited LPS-stimulated production of H-I and TNF-alpha. These inhibitory effects were attributed to the organic extracts of DEP. In contrast, stimulation of AM production of TNF-alpha by IFN-gamma was not affected by DEP exposure. In summary, evidence that DEP enhanced the production of IL-1 by AM in vitro suggests that this proinflammatory cytokine may play a role in the pulmonary response to DEP inhalation. The suppressive response of DEP-pretreated AM to LPS stimulation may be a contributing factor to the impairment of pulmonary defense system after prolonged DEP exposure.

The organic component of diesel exhaust particles and phenanthrene, a major polyaromatic hydrocarbon constituent, enhances IgE production by IgE-secreting EBV-transformed human B cells in vitro

Suspended airborne particulate matter such as diesel exhaust particles (DEP) have been implicated in the increased incidence of respiratory allergic diseases that has occurred over the past century. Studies in vitro and in vivo have shown that DEP may enhance allergic antibody (IgE) expression. DEP contain a wide spectrum of polycyclic aromatic hydrocarbons (PAH) that have been reported to have direct effects on the immune system, including the modulation of IgE production using various human and murine cell populations. We investigated the effects of the organic extract of DEP (PAH-DEP) and particularly, phenanthrene, a major component of DEP, in vitro on IgE production by 2C4/F3, a human Epstein-Barr virus transformed isotype switched, IgE producing B cell line. Phenanthrene consistently enhanced 2C4/F3 IgE production two- to threefold. This in vitro enhancement was associated with an increased expression of total IgE mRNA. Furthermore, the pattern of mRNA's coding for distinct isoforms of the epsilon chain was altered by both DEP-PAH and phenanthrene. While phenanthrene increased the level of productive epsilon transcripts, it did not increase epsilon germ line transcription. These effects were not due to an alteration of the cell cycle. Unstimulated 2C4/F3 cells contained detectable mRNA for IL6, IL10, TNF-alpha, and interestingly IL4; however, addition of PAH-DEP or phenanthrene did not significantly alter the level of these cytokines and thus did not appear to account for our findings. Thus, we have used our in vitro model to dissect the mechanism of DEP-PAH on IgE production in postswitch IgE producing cells and shown that phenanthrene, an important component in DEP and other pollutants, can act in a similar manner.

Pathogenesis of allergic rhinitis

Allergic rhinitis is an increasing problem for which new and exciting therapies are being developed. These can be understood through an appreciation of the newer concepts of pathogenesis of allergic rhinitis. Allergen induces Th2 lymphocyte proliferation in persons with allergies with the release of their characteristic combination of cytokines including IL-3, IL-4, IL-5, IL-9, IL-10, and IL-13. These substances promote IgE and mast cell production. Mucosal mast cells that produce IL-4, IL-5, IL-6, and tryptase proliferate in the allergic epithelium. Inflammatory mediators and cytokines upregulate endothelial cell adhesion markers, such as vascular cell adhesion molecule-1. Chemoattractants, including eotaxin, IL-5, and RANTES, lead to characteristic infiltration by eosinophils, basophils, Th2 lymphocytes, and mast cells in chronic allergic rhinitis. As our understanding of the basic pathophysiologic features of allergic rhinitis continues to increase, the development of new diagnostic and treatment strategies may allow more effective modulation of the immune system, the atopic disease process, and the associated morbidity.

The role of diesel exhaust particles and their associated polyaromatic hydrocarbons in the induction of allergic airway disease

The increase in allergic airway disease has paralleled the increase in the use of fossil fuels. Studies were undertaken to examine whether extracts of polyaromatic hydrocarbons (PAH) from diesel exhaust particles (DEP) (PAH-DEP) acted as mucosal adjuvants to help initiate or enhance immunoglobulin E (IgE) production in response to common inhaled allergens. In vitro studies demonstrated that PAH-DEP enhanced IgE production by tonsillar B-cells in the presence of interleukin-4 (IL-4) and CD40 monoclonal antibody, and altered the nature of the IgE produced, i.e. a decrease in the CH4'-CHe5 variant, a marker for differentiation of IgE-producing B-cells, and an increase in the M2' variant. In vivo nasal provocation studies using 0.30 mg DEP in saline also showed enhanced IgE production in the human upper respiratory mucosa, accompanied by a reduced CH4'-CHe5 mRNA splice variant. The effects of DEP were also isotype-specific, with no effect on IgG, IgA, IgM, or albumin, but it produced a small increase in the IgG4 subclass. The ability of DEP to act as an adjuvant to the ragweed allergen Amb a I was examined by nasal provocation in ragweed allergic subjects using 0.3 mg DEP, Amb a I, or both. Although allergen and DEP each enhanced ragweed-specific IgE, DEP plus allergen promoted a 16-times greater antigen-specific IgE production. Nasal challenge with DEP also influenced cytokine production. Ragweed challenge resulted in a weak response, DEP challenge caused a strong but non-specific response, while allergen plus DEP caused a significant increase in the expression of mRNA for TH0 and TH2-type cytokines (IL-4, IL-5, IL-6, IL-10, IL-13) with a pronounced inhibitory effect on IFN-gamma gene expression. These studies suggest that DEP can enhance B-cell differentiation, and by initiating and elevating IgE production, may play an important role in the increased incidence of allergic airway disease.

Mechanisms of pollution-induced airway disease: in vitro studies in the upper and lower airways

Evidence from both epidemiological and laboratory-based studies suggests that increased exposure to liquid petroleum and gas-derived air pollutants [nitrogen dioxide (NO2), ozone, and respirable particulate matter] may play a role in the clinical manifestation of both allergic and non-allergic airway disease. The mechanisms and cell types involved in pollutant-mediated effects in the airways, however, are not clear. In vitro studies have suggested that human fibroblasts, B-lymphocytes, alveolar macrophages, and epithelial cells/cell lines may be involved. Studies of fibroblasts and macrophages have demonstrated that exposure to ozone results in decreased cell viability and increased release of pro-inflammatory mediators from macrophages. Similarly, studies of B-lymphocytes have demonstrated that exposure to diesel exhaust particles (DEP) enhances the synthesis of immunoglobulin E by these cells. The airway epithelial cells have received the greatest attention in mechanistic studies of air pollution-induced airway disease and suggest that these cells are likely to play a pivotal role in the pathogenesis of airways disease. Various studies have demonstrated that exposure of nasal or bronchial epithelial cells to NO2, ozone, and DEP results in significant synthesis and release of pro-inflammatory mediators, including eicosanoids, cytokines, and adhesion molecules. Additionally, evidence suggests that epithelial cells of atopic individuals release significantly greater amounts of cytokines such as granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-6 (IL-6), IL-8, and regulated on activation, normal T-cell expressed and secreted (RANTES), on exposure to NO2 and ozone. Studies investigating the biological relevance of epithelial cell-derived pro-inflammatory mediators have shown that these enhance eosinophil chemotaxis and eosinophil adherence to endothelial cells, suggesting that pollution-induced inflammation of the airways is likely to be influenced by modulation of epithelial synthesis and release of these mediators.

Serum immunoglobulin E and hyaluronate levels in children living along major roads

To assess the effects of automobile exhaust on human health, we determined serum concentrations of total immunoglobulin E and hyaluronate in 185 schoolchildren who lived in a district that contained major roads. Serum immunoglobulin E levels were elevated in children who had asthma or wheezing, but levels did not differ with respect to distance of their homes from the major roads. Serum hyaluronate levels were higher in children who lived less than 50 m from the roadside, compared with children who resided a greater distance from roads. The difference, however, was significant only in a subgroup of children in whom immunoglobulin E levels exceeded 250 IU/ml. Our results suggest that serum hyaluronate levels in children reflect the effects of traffic-related air pollution. Children with high immunoglobulin E levels appeared to be particularly susceptible to the effects of automobile exhaust.

Global increases in allergic respiratory disease: the possible role of diesel exhaust particles

OBJECTIVE

Reading this article will enable the readers to recognize and evaluate i e potential relationship between allergic respiratory disease and polyaromatic hydrocarbons as air pollutants from industrial and automotive fuel sources. In this article we review the long-term trends in the prevalence of allergic airway diseases (rhinitis and asthma). We then examine the epidemiologic and other research data relating to the role that hydrocarbon fuel emissions may have had on allergic respiratory disease.

DESIGN

Published literature on the relationship between specific air pollutants and trends in allergic respiratory disease were reviewed. Reports of research on pollutant effects on allergic antibody (IgE) were also studied. In both cases, the Melvyl-Medline database since 1975 was used for literature searches. Older references were identified from the bibliographies of relevant articles and books and with the help of the rare books collection at UCLA's Louis M. Darling Biomedical library.

RESULTS

Examination of the historical record indicates that allergic rhinitis and allergic asthma have significantly increased in prevalence over the past two centuries. Although the reasons for this increase are not fully elucidated, epidemiologic data suggest that certain pollutants such as those produced from the burning of fossil fuels may have played an important role in the prevalence changes. Also important are studies showing that diesel exhaust, a prototypical fossil fuel, is able to enhance in vitro and in vivo IgE production.

CONCLUSION

Increased levels of the compounds resulting from fossil fuel combustion may be partly responsible for the increased prevalence of allergic respiratory disease. If the nature of these compounds and the mechanisms by which they exacerbate allergic disease can be identified, steps can be taken to reduce the production or the impact of these allergy producing compounds.