In vitro study of pro-inflammatory and anti-tumour properties of microvesicles from bacterial cell wall of Pantoea agglomerans

Radoslaw Spiewak¹, Jacek Dutkiewicz²

¹Institute of Dermatology Ltd., Krakow, Poland
²Department of Occupational Biohazards, Institute of Agricultural Medicine, Lublin, Poland

Exposure to organic dust is widely accepted as a major cause for a range of lung disorders, including organic dust toxic syndrome (ODTS, syn. toxic pneumonitis), chronic obstructive pulmonary disease (COPD), increased airway responsiveness, asthma, and granulomatous pneumonitis (syn. allergic alveolitis, hypersensitivity pneumonitis) [8, 31, 35, 39, 42]. A connection has also been described between organic dust exposure and inflammatory skin disease [5, 22, 51, 52, 53, 56, 57, 58, 59]. Epidemiological data suggest, however, also a possible positive effect of organic dust exposure on human health: workers exposed to organic dust seem at lower risk for lung cancer [29, 30]. Also, exposure to organic dust in early life is regarded to reduce atopy and prevent respiratory allergies in children [40, 42]. Among candidate components responsible for both adverse and benefi cial biological effects of exposure to organic dust are Gram-negative bacteria and their toxins, of which lipopolysaccharides (LPS, syn. endotoxins) attract the most attention of researchers [10, 21, 27, 31, 35, 36, 40, 42, 43, 44, 64]. Disruption of Gram-negative bacteria produces large amounts of spherical, endotoxin-containing structures measuring 30-50 nm in diameter. These structures, referred to as "microvesicles" (MV) or "microglobules", emerge by fragmentation of the outer membrane of the bacterial cell wall. They occur abundantly in wood dust, grain dust and other organic dusts [13, 16, 17]. Animal studies have demonstrated that repeated inhalation exposures to endotoxin-containing microvesicles (MV) lead to substantial increase of circulating interferon (IFN) and tumour necrosis factor alpha (TNF-α), significantly higher than in animals exposed to respective doses of pure endotoxin [15, 45].

The aim of the present work was to study in vitro the pro-inflammatory and anti-tumour properties of endotoxin containing microvesicles (MV) on human leukocytes. The present study focused on the following possible effects of microvesicles: secretion of interferon gamma (IFN-γ) and tumour necrosis factor alpha (TNF-α), proliferation, and expression of cell surface markers on human peripheral blood mononuclear cells (PBMC).

Materials and Methods

Production of microvesicles. Microvesicles were produced as described earlier [15, 16, 45]. They were separated from bacterial mass in sucrose density gradients, prepared with the Hoefer SG Gradient Maker (Hoefer Scientific Instruments, San Francisco, CA, USA). Pantoea agglomerans (synonyms: Enterobacter agglomerans, Erwinia herbicola), strain Z-11, originally isolated from settled grain dust, was grown on nutrient agar in Roux bottles, for 72 h at 35°C. Bacterial cell mass was harvested from each bottle with 12 ml phosphate buffered saline, pH 7.4, containing 0.001% gelatine. The washes from 10 bottles were pooled and centrifuged. The resulting bacterial pellet was then resuspended in 5 ml buffer, and thereafter each 1 ml was placed on 20 ml sucrose density gradient (ranging from 5-30%) and centrifuged for 15 min at 3,500 × g in a 25 ml tube. After this procedure, a pellet of whole cells was visible and a broad turbid layer in the lower third of the gradient, consisting mostly of particles smaller than whole cells. This layer was carefully decanted, pelleted by centrifugation, resuspended in 0.5 ml buffer, placed in a tube with sucrose gradient of higher density (6 ml, range from 10-45%), and centrifuged again at 3,500 × g for 30 min, which resulted in the formation of a more defined band about 5-8 mm thick, in the lower quarter of the tube (Fig. 1). This fraction was decanted, centrifuged, checked by electron microscopy (Figs. 2-3), and finally lyophilized as microvesicles (MV) for further studies. The endotoxin activity of MV was measured using the Limulus Amebocyte Lysate (LAL) test, as described elsewhere [46], and the endotoxin content finally calculated as 31.25 mg pure endotoxin per 1 g MV (3.125%).

Cell cultures. Peripheral blood mononuclear cells (PBMC) used for the experiments were obtained from 5 healthy volunteers (2 men and 3 women, aged 38-51 years) with no history of exposure to organic dusts. PBMC were separated from the participants' blood samples through density gradient centrifugation in Ficoll-Paque Plus (Amersham, Uppsala, Sweden). Immediately after separation and washing, the cells were counted and tested for viability by trypane blue exclusion (≥97% viable cells were found in each cell batch). The cells were cultured at 37°C, 95% RH and 5% CO2 in IMDM medium (Cambrex, Verviers, Belgium) supplemented with penicillin 50 U/ml and streptomycin 50 µg/ml (Lonza, Verviers, Belgium) and 1,4-dithiothreitol 7.8 µg/ml (Sigma-Aldrich Chemie, Steinheim, Germany) [55]. The fi nal cell density was 5 × 103 cells/well (25,000 cells/ml) for ELISpot assay, and 10⁵ cells/well (500,000 cells/ml) for ELISA and LPT assays.

Enzyme-Linked Immunosorbent Assay (ELISA). PBMC for ELISA were cultured at 10⁵ cells/well in triplicate for 6 h, 24 h, 3 days, and 5 days, without addition of MV and with each concentration of the 5-fold dilution series of MV: 0.48, 2.4, 12, 60, 300, and 1,500 µg/ml. After an appropriate time, supernatants were collected and kept at -20°C until cytokine determination was performed with ELISA. IFN-γ and TNF-α were measured with PeliKine™-compact human IFN-γ and TNF-α ELISA kits, respectively and PeliKine™-Tool supplementary reagents set (Sanquin, Amsterdam, The Netherlands), according to the manufacturer's recommendations. According to manufacturer's information, the detection levels for both cytokines were 1 pg/ml. The absorbance was measured at 450 nm wavelength with Microplate Autoreader ELX808, and the final cytokine concentrations were calculated automatically by the KC Junior Software (Bio-Tek, Winooski, VT, USA).

Enzyme-Linked Immunospot Assay (ELISpot). Coating antibodies and detection antibodies for IFN-γ and TNF-α, and streptavidin-alkaline phosphatase (s-ALP) conjugate were supplied with ELISpot kits (Mabtech, Näcka, Sweden). The cells were cultured at 5 × 103 cells/well in 96-well PVDF microfi lter plates (Millipore, Molsheim, France), each preincubated with coating antibodies for IFN-γ or TNF-α, following the manufacturers' recommendations. For each donor, PBMC were cultured in triplicate for 6 h, 24 h, 3 days, and 5 days, without addition of MV and with each concentration of a 5-fold dilution series of MV: 0.48, 2.4, 12, 60, 300, and 1,500 µg/ml. At the end of the culture period, the cells were disposed from the plates. Cytokines bound to the membrane during the culture were visualized using respective biotinylated detection antibodies, s-ALP conjugate, and finally the BCIP/NBT colour substrate (Mabtech, Näcka, Sweden). Spots on the membrane, each denoting one cell secreting cytokine of interest, were counted automatically using the A.EL.VIS Eli.Scan Elispot scanner with Eli.Analyse software (A.EL.VIS, Hannover, Germany). The ELISpot technique is capable of detecting 1 cell secreting cytokine of interest out of 1 million cultured cells [48].

Lymphocyte proliferation test (LPT). PBMC were cultured at 10⁵ cells/well in triplicate for 6 h, 24 h, 3 days, and 5 days, without addition of MV and with each concentration of the 5-fold dilution series of MV: 0.48, 2.4, 12, 60, 300, and 1500 µg/ml. The radiolabel for proliferation, ³H-thymidine (Amersham, Little Chalfont, UK) was added to the cultures at the starting point with the final radioactivity 0.625 µCi/well. After an appropriate time, the cell cultures were frozen and kept at -20°C until measurement. The amount of incorporated radioactivity was measured using microplate scintillation counter TopCount NXT with scintillation fluid Microscint O (Packard Biosciences, Downers Grove, IL, USA).

Flow cytometry analysis (FACS). Due to high workload and cost of the analyses, the number of donors tested in this part of the study was limited to 3, and the tested range of MV concentration was 0.48-300 µg/ml with a 25-fold step. Donors' PBMC were cultured at 10⁶ cells/ml (5 ml per culture) for 1, 3, and 5 days without addition of MV and with each 0.48, 12, and 300 µg/ml microvesicles. After the appropriate incubation periods, cell samples (each 10⁵ cells) were stained for flow fluorocytometric analyses with following antibodies: anti-CD8-Cy5 (Sanquin, Amsterdam, The Netherlands), anti-CD14-FITC (BD Pharmingen, San Diego, CA, USA), anti-CD16-PE (Sanquin), anti-CD25-FITC (BD Pharmingen), anti-CD69-Cy5 (BD Pharmingen), anti-CD80-PE (BD Pharmingen), anti-CD83-PE (Beckman Coulter, Fullerton, CA, USA), anti-HLA-DR-FITC (BD Pharmingen). In order to check for non-specific binding, the cell samples were stained with respective isotype antibodies. For detection of apoptotic cells, the samples were stained with Annexin-V-FITC (Bender MedSystems, Vienna, Austria), and propidium iodide (PI, Sigma-Aldrich, Saint Louis, MO, USA). The staining procedure was carried out following recommendations of respective manufacturers. The fl ow cytometric measurements were carried out using FACSCalibur 3 CA (Becton-Dickinson, Mountain View, CA, USA) with Cell Quest software for data acquisition.

Data analysis. In order to detect differences in multiple related samples (series of MV dilutions), the Friedman test was carried out with raw data [23]. Statistical package SPSS+ for Windows (SPSS Inc, Chicago, IL, USA) was used for the above analyses. As there were big interindividual differences in IFN-γ and TNF-α secretion between donors (up to 27-fold), the ELISpot, ELISA, and LPT results were presented on the graphs as indexes, i.e. results for cultures with various MV concentrations were each divided by values measured in the negative controls (culture without addition of MV). Regarding flow cytometry analyses, due to previously-mentioned reduction in the number of donors and measuring points on the dose-response curve, a statistical estimation of significance was not feasible. Therefore, only dose-dependent phenomenon consistently seen in all 3 donors was arbitrarily considered as relevant and presented in this article.

Results

In ELISA tests, the measured concentrations were within the range of 1-2495 pg/ml for IFN-γ, and 61-5087 pg/ml for TNF-α with up to 27-fold differences in baseline values observed between donors. In order to make comparisons possible, trends in Figure 4 are demonstrated as means of individual values indexed against the mean baseline (negative control, i.e. spontaneous cytokine secretion by unstimulated cells). A clear dose-dependent response to MV in IFN-γ production was seen after 24 hours, with a more than 2-fold increase observed already at the lowest MV concentration tested: 0.48 µg/ml (p=0.042). As for TNF-α, a signifi cant (p=0.05) increase in the cytokine production was seen after 3 days, with a 2-fold increase only at the highest MV concentrations of 1,500 µg/ml. The ELISpot tests results have confirmed the ELISA results (Fig. 5). A clear and significant dose-dependent increase in cell proliferation in response to MV was detectable after 5 days (p=0.001).

Regarding expression of cell surface markers, samples from only 3 donors were tested at this stage due to high workload and cost of analyses with a broad array of the markers. Therefore, an estimation of statistical significance was not feasible and only dose-dependent phenomena consistently seen in all 3 donors were considered relevant. Such a phenomenon was the decrease in percentage of CD14(+)CD83(+) cells observed after 24 h of incubation in the presence of MV. The fraction of CD14(+)CD83(+) within the monocyte fraction (defined on the basis of forward and sideward scatter of the laser beam) ranged from 0.78-4.08% with consistent dose-response relationship (decrease of the percentage at increasing MV concentrations) in all 3 donors (Fig. 6). The percentages of CD14(+)CD83(+) cells were within the range 1.08-2.67% after 3 days of culture, and 2.45-9.77% after 5 days; however, no consistent dose-response effects were seen at those time points.

Discussion

In a series of experiments, we have demonstrated the dose-dependent influence of Gram-negative bacterial microvesicles (MV) on cultures of human peripheral blood mononuclear cells (PBMC). IFN-γ production was increased relatively early (after 24 hrs), and at lowest MV doses tested, whereas TNF-α became upregulated after 3 days, and only by MV doses 125-times higher. Therefore, it seems that depending on the intensity and duration of exposure, microvesicles may upregulate IFN-γ alone, or IFN-γ and TNF-α together. IFN-γ and TNF-α are potent inflammatory cytokines that act synergistically in a range of immunological processes. With respect to this study, perhaps most interesting seems their synergistic anti-tumour effect against lung cancer cells [4, 41, 61]. This might suggest that the protective effect of organic dust exposure found in some epidemiological observations may depend on the dose of inhaled MV.

IFN-γ belongs to the family of interferons, characterised by their ability to protect cells from viral infections. Interferons are divided into 2 classes: Type I IFN includes IFN-α and IFN-β, which are the classical interferons secreted in response to viral infections. The only member of type II IFN subclass is IFN-γ (also referred to as "type II interferon" or "immune IFN"), which is neither genetically nor structurally related to the type I. IFN-γ induces most of the biologic effects typical to other interferons; however, its specific antiviral activity is lower, and immunomodulatory activity higher [18]. Moreover, IFN-γ stimulates MHC class II antigens, which is in contrast to type I interferons [1]. Cells capable of producing large amounts of IFN-γ include natural killer (NK) cells, CD4+ T helper-1 (Th1) cells, and CD8+ T cytotoxic cells [6, 18]. Less potent sources of IFN-γ are also γδ T cells, NKT cells, macrophages, dendritic cells, naive CD4+ T cells, and B cells [19, 62]. According to Gallin et al. [20], the key immunoregulatory roles of IFN-γ are: (1) improved antigen presentation; (2) enhanced killing of intracellular pathogens, which induces the synthesis of enzymes in phagocytes that are involved in the generation of reactive oxidants (eg, superoxide, hydrogen peroxide, and nitric oxide) that are crucial for the killing of intracellular and some extracellular infectious agents; (3) increased capacity for microbial killing; and (4) enhanced recruitment of leukocyte-enhanced macrophage activity, and increased intracellular concentration of antimicrobials.

TNF is a pleiotropic proinflammatory cytokine that plays an important role in the induction of other cytokines, cell proliferation, differentiation, necrosis, and apoptosis. TNF is either membrane-bound or secreted. Main sources are activated macrophages, lymphocytes, natural killer cells, and epithelial cells. Three classes of TNFs have been identified: TNF-α, lymphotoxin-α (LT-α), and LT-β, all of which are bioactive as trimers [37]. The biological functions of TNF-α are too many to be discussed in this article. Most important for the present study is the generally accepted pivotal role of TNF-α in anti-tumour immunity [63]. This picture, however, is not fully clear: There are also hints that in certain situations TNF-α may paradoxically contribute to cancer development [2].

Human CD83 is a 45-kDa glycoprotein belonging to the immunoglobulin superfamily, generally accepted as surface marker for activated dendritic cells (DC) [3]. In the present study, the decrease in percentage of DC (CD14+CD83+) within the monocyte fraction after 1 day of culturing with MV may seem paradoxical. However, it can be explained with the fact that a certain fraction of LPS-stimulated CD14(+) monocytes undergoes activation into Mφ macrophages (CD14+CD70+CD83-HLA-DR-), spontaneously producing large amounts of TNF-α and matrix metalloproteinase 9 (MMP-9) [26]. MMP-9 is collagenase, a neutral proteinase involved in the breakdown and remodelling of extracellular matrix (ECM) [9]. MMPs also cleave a variety of non-ECM proteins, including cytokines, chemokines, and growth factors, activating or inactivating these. Upregulation of matrix metalloproteinases is observed in a variety of destructive processes, including cardiovascular, inflammatory, autoimmune, and neoplastic diseases [25].

Environmental Gram-negative bacteria and their products are abundantly present in various types of occupational bioaerosols: grain dust, flax dust, wood dust, herb dust, waste and sewage aerosols [11, 12, 17]. Gram-negative bacteria and their products can also be encountered in non-occupational environments, e.g. they are present on airborne pollen [47, 54, 60]. Bacterial endotoxin typically occurs in the environment in the form of microvesicles, which are composed of lipopolysaccharides, proteins and phospholipids [7, 17]. The results of the present work show that the isolated fraction of endotoxin-containing microvesicles exerts a significant effect on the cytokine production by human cells in vitro. These data confi rm the results of the earlier studies by Skórska et al. [45] and Dutkiewicz et al. [15] who demonstrated in animal experiments strong stimulation effects of endotoxin-containing microvesicles of the Rahnella spp. and Pantoea agglomerans on cytokine production. All these results corroborate those obtained by Rylander [38] and Milanowski [32, 33] who reported that cell-bound endotoxin shows stronger biological activity than purified LPS.

It appears that the biological activity of endotoxin also depends on the species of bacteria, and that potency of the Pantoea agglomerans endotoxin is greater compared to other Gram-negative bacteria [10, 14, 24]. This species exhibits also strong allergenic properties and could be a cause of work-related respiratory and skin disorders in people exposed to organic dusts [11, 28, 34, 49, 59]. The fact that the dust-borne endotoxin of Pantoea agglomerans occurs in the form of fine, submicroscopic microvesicles [16, 17] easily penetrating into alveoli, increases the potential risk of disorders after exposure to these bacteria. On the other side, however, this fact might increase non-specific immunity against neoplastic diseases and suppress atopic predisposition in exposed people. The present work, demonstrating the immunomodulatory effects of Pantoea agglomerans endotoxin-containing microvesicles on human cells proves a possibility of both adverse and beneficiary effects in people inhaling these structures.

Conclusions

Secretion of IFN-γ and TNF-α by peripheral blood mononuclear cells (PBMC) is triggered at different concentrations of microvesicles. At lower concentrations, only IFN-γ is upregulated, whereas at higher concentrations both IFN-γ and TNF-α are secreted. Increase of IFN-γ begins between 6 and 24 hours of stimulation, whereas increased production of TNF-α begins between 1 and 3 days. These data suggest that biological effects of organic dust may be dependent of the duration of exposure and the inhaled dose, which might offer some hint for future epidemiological studies.

Acknowledgements

The ELISpot Scanner and ELISA Reader used in this study were donated by the Spiewak Family to commemorate the late Karolina Spiewak (1904-1989), a devoted Polish mother, whose heroic and extraordinary achievement was to ensure survival for 9 out of her 10 children from the Soviet deportation to Siberian Gulags during World War II.

Initial results of this study were presented at 2 scientific conferences in 2006 [50, 51].

References

1. Antoniou KM, Ferdoutsis E, Bouros D: Interferons and their application in the diseases of the lung. Chest 2003, 123, 209-216. 2. Balkwill F: TNF-α in promotion and progression of cancer. Cancer Metastasis Rev 2006, 25, 409-416. 3. Banchereau J, Steinman RM: Dendritic cells and the control of immunity. Nature 1998, 392(6673), 245-252. 4. Beaupain R, Martyre MC: Short- and long-term synergistic effects of human tumor necrosis factor and interferon-gamma on A549 human lung cancer cells maintained in three-dimensional culture. Anticancer Res 1990, 10, 1061-1066. 5. Bender C, Peck S: Health symptoms reported during BTK spraying spring 1994 in the capital regional district. Environ Health Rev 1996, 40, 42-44. 6. Boehm U, Klamp T, Groot M, Howard JC: Cellular responses to interferon-gamma. Annu Rev Immunol 1997, 15, 749-795. 7. Burrell R: Immunotoxic reactions in the agricultural environment. Ann Agric Environ Med 1995, 2, 11-20. 8. Bünger J, Antlauf-Lammers M, Schulz TG, Westphal GA, Müller MM, Ruhnau P, Hallier E: Health complaints and immunological markers of exposure to bioaerosols among biowaste collectors and compost workers. Occup Environ Med 2000, 57, 458-464. 9. Chakrabarti S, Patel KD: Matrix metalloproteinase-2 (MMP-2) and MMP-9 in pulmonary pathology. Exp Lung Res 2005, 31, 599-621. 10. Dutkiewicz J: Studies on endotoxins of Erwinia herbicola and their biological activity. Zbl Bakt Hyg I Abt. Orig A 1976, 236, 487-508. 11. Dutkiewicz J: Airborne bacteria as occupational allergens. In: Frankland AW, Stix E, Ziegler H (Eds): The 1st International Conference on Aerobiology, München 13-15 August 1978: Proceedings, 232-242. Umweltbundesamt Berichte 5/79. Erich Schmidt Verlag, Berlin 1980. 12. Dutkiewicz J: Bacteria and fungi in organic dust as potential health hazard. Ann Agric Environ Med 1997, 4, 11-16. 13. Dutkiewicz J, Krysinska-Traczyk E, Skórska C, Sitkowska J, Prazmo Z, Urbanowicz B: Exposure of agricultural workers to airborne microorganisms and endotoxin during handling of various vegetable products. Aerobiologia 2000, 16, 193-198. 14. Dutkiewicz J, Skórska C, Sitkowska J, Ochalska B, Kaczmarski F: Properties of the endotoxins produced by various gram-negative bacteria present in occupational environments. In: Jacobs RR, Wakelyn PJ, Rylander R, Burrell R (Eds): Cotton Dust (Proceedings of the 12th Cotton Dust Research Conference and of the Endotoxin Inhalation Workshop, 28-30 September 1987, Clearwater, Florida), 187-189. National Cotton Council, Memphis, Tennessee, 1988. 15. Dutkiewicz J, Skórska C, Burrell R, Szuster-Ciesielska A, Sitkowska J: Immunostimulative effects of repeated inhalation exposure to microvesicle-bound endotoxin of Pantoea agglomerans. Ann Agric Environ Med 2005, 12, 289-294. 16. Dutkiewicz J, Tucker J, Woodfork K, Burrell R: The identifi cation of extracellular endotoxin molecules by immunoelectron microscopy. In: Jacobs RR, Wakelyn PJ (Eds): Cotton Dust (Proceedings of the 13th Cotton Dust Research Conference, 5-6 January 1989, Nashville, TN), 111- 114. National Cotton Council, Memphis, Tennessee 1989. 17. Dutkiewicz J, Tucker J, Burrell R, Olenchock SA, Schwegler-Berry D, Keller III GE, Ochalska B, Kaczmarski F, Skórska C: Ultrastructure of the endotoxin produced by Gram-negative bacteria associated with organic dusts. System Appl Microbiol 1992, 15, 474-485. 18. Farrar MA, Schreiber RD: The molecular cell biology of interferon- γ and its receptor. Annu Rev Immunol 1993, 11, 571-611. 19. Frucht DM, Fukao T, Bogdan C, Schindler H, O'Shea JJ, Koyasu S: IFN-gamma production by antigen-presenting cells: mechanisms emerge. Trends Immunol 2001, 22, 556-560. 20. Gallin JI, Farber JM, Holland SM, Nutman TB: Interferon-γ in the management of infectious diseases. Ann Intern Med 1995, 123, 216-224. 21. George CL, Jin H, Wohlford-Lenane CL, O'Neill ME, Phipps JC, O'Shaughnessy P, Kline JN, Thorne PS, Schwartz DA: Endotoxin responsiveness and subchronic grain dust-induced airway disease. Am J Physiol Lung Cell Mol Physiol 2001, 280, L203-213. 22. Green M, Heumann M, Sokolow R, Foster LR, Bryant R, Skeels M: Public health implications of the microbial pesticide Bacillus thuringiensis: an epidemiological study, Oregon, 1985-86. Am J Public Health 1990, 80, 848-852. 23. Green SB, Salkind NJ, Akey TM: Using SPSS for Windows. 2nd Edition. Prentice Hall, Upper Saddle River, NJ 2000, 384-392. 24. Helander I, Saxen H, Salkinoja-Salonen M, Rylander R: Pulmonary toxicity of endotoxins: comparison of lipopolysaccharides from various bacterial species. Infect Immun 1982, 35, 528-532. 25. Hrabec E, Naduk J, Strek M, Hrabec Z: Type IV collagenases (MMP-2 and MMP-9) and their substrates-intracellular proteins, hormones, cytokines, chemokines and their receptors. Postêpy Biochem 2007, 53, 37-45 (in Polish). 26. Iwamoto S, Iwai S, Tsujiyama K, Kurahashi C, Takeshita K, Naoe M, Masunaga A, Ogawa Y, Oguchi K, Miyazaki A: TNF-α drives human CD14+ monocytes to differentiate into CD70+ dendritic cells evoking Th1 and Th17 responses. J Immunol 2007, 179, 1449-1457. 27. Kline JN, Jagielo PJ, Watt JL, Schwartz DA: Bronchial hyperreactivity is associated with enhanced grain dust-induced airfl ow obstruction. J Appl Physiol 2000, 89, 1172-1178. 28. Kus L: [Allergic alveolitis in effect of the exposure to antigens present in grain dust: An experimental and clinical study.] Med Wiejska 1980, 15, 73-80 (in Polish). 29. Laakkonen A, Pukkala E: Cancer incidence among Finnish farmers, 1995-2005. Scand J Work Environ Health 2008, 34, 73-79. 30. Lange JH, Mastrangelo G, Fedeli U, Fadda E, Rylander R, Lee E: Endotoxin exposure and lung cancer mortality by type of farming: is there a hidden dose-response relationship? Ann Agric Environ Med 2003, 10, 229-232. 31. Madsen AM: Airborne endotoxin in different background environments and seasons. Ann Agric Environ Med 2006, 13, 81-86. 32. Milanowski J: Effects of Pantoea agglomerans on the respiratory system. Part I. Studies in vitro. Ann Agric Environ Med 1994, 1, 44-51. 33. Milanowski J: Effects of Pantoea agglomerans on the respiratory system. Part II. Studies in vivo. Ann Agric Environ Med 1994, 1, 52-56. 34. Milanowski J, Dutkiewicz J, Potoczna H, Kus L, Urbanowicz B: Allergic alveolitis among agricultural workers in eastern Poland: A study of twenty cases. Ann Agric Environ Med 1998, 5, 31-43. 35. Omland O: Exposure and respiratory health in farming in temperate zones - a review of the literature. Ann Agric Environ Med 2002, 9, 119-136. 36. Pomorska D, Larsson L, Skórska C, Sitkowska J, Dutkiewicz J: Levels of bacterial endotoxin in air of animal houses determined with the use of gas chromatography - mass spectrometry and Limulus test. Ann Agric Environ Med 2007, 14, 291-298. 37. Rahman MM, McFadden G: Modulation of tumor necrosis factor by microbial pathogens. PLoS Pathog 2006, Feb, 2(2), e4. 38. Rylander R: Toxicity of inhaled and isolated cell bound endotoxin. In: Jacobs RR, Wakelyn PJ, Rylander R, Burrel R (Eds): Cotton Dust (Proceedings of the 12th Cotton Dust Research Conference and of the Endotoxin Inhalation Workshop, 28-30 September 1987, Clearwater, Florida), 202-203. National Cotton Council, Memphis, Tennessee 1988. 39. Rylander R: Organic dust and lung disease: the role of infl ammation. Ann Agric Environ Med 1994, 1, 7-10. 40. Schierl R, Heise A, Egger U, Schneider F, Eichelser R, Neser S, Nowak D: Endotoxin concentration in modern animal houses in southern Bavaria. Ann Agric Environ Med 2007, 14, 129-136. 41. Shiiki S, Fuchimoto S, Orita K: Synergistic antitumor effects of natural human tumor necrosis factor-alpha and natural human interferonalpha or -gamma on human cancer cell lines. Res Commun Chem Pathol Pharmacol 1989, 64, 87-97. 42. Schulze A, van Strien R, Ehrenstein V, Schierl R, Küchenhoff H, Radon K: Ambient endotoxin level in an area with intensive livestock production. Ann Agric Environ Med 2006, 13, 87-91. 43. Skórska C, Mackiewicz B, Dutkiewicz J, Krysinska-Traczyk E, Milanowski J, Feltovich H, Lange J, Thorne P: Effects of exposure to grain dust in Polish farmers: work-related symptoms and immunologic response to microbial antigens associated with dust. Ann Agric Environ Med 1998, 5, 147-153. 44. Skórska C, Mackiewicz B, Góra A, Golec M, Dutkiewicz J: Health effects of inhalation exposure to organic dust in hops farmers. Ann Univ Mariae Curie Sklodowska [Med] 2003, 58, 459-465. 45. Skórska C, Sitkowska J, Burrell R, Szuster-Ciesielska A, Dutkiewicz J: Effects of repeated inhalation exposure to microvesicle-bound endotoxin. Ann Agric Environ Med 1996, 3, 61-65. 46. Skórska C, Sitkowska J, Krysinska-Traczyk E, Cholewa G, Dutkiewicz J: Exposure to airborne microorganisms, dust and endotoxin during processing of peppermint and chamomile herbs on farms. Ann Agric Environ Med 2005, 12, 281-288. 47. Spiewak R: Does microfl ora present on pollen grains play a role in respiratory pollen allergy? Allergy 1997, 52(Suppl 37), 56. 48. Spiewak R: [The immunosorbent immunospot assay (ELISPOT): Perspectives for use in allergology and immunology.] Alergol Immunol 2007, 4, 77-81 (in Polish). 49. Spiewak R, Dutkiewicz J: A farmer's occupational airborne contact dermatitis masqueraded by coexisting rosacea: delayed diagnosis and legal acknowledgement. Ann Agric Environ Med 2004, 11, 329-333. 50. Spiewak R, Dutkiewicz J: Immunomodulatory effects of the microvesicles from bacterial cell wall of Pantoea agglomerans. In: Valenta R, Akdis C, Bohle B (Eds): XXV Congress of the European Academy of Allergology and Clinical Immunology. EAACI 2006, Vienna, Austria, 94. 51. Spiewak R, Dutkiewicz J: Proinfl ammatory effects of bacterial cell wall of Pantoea agglomerans: A possible explanation of airborne dermatitis to bioaerosols. J Invest Dermatol 2006, 126 (Suppl. 3), s54. 52. Spiewak R, Góra A, Dutkiewicz J: Work-related allergic skin symptoms among hop growers. Allergy 2001, 56 (Suppl. 68), 101. 53. Spiewak R, Góra A, Dutkiewicz J: Work-related skin symptoms and type I allergy among eastern-Polish farmers growing hops and other crops. Ann Agric Environ Med 2001, 8, 51-56. 54. Spiewak R, Krysinska-Traczyk E, Sitkowska J, Dutkiewicz J: Microflora of allergenic pollens - a preliminary study. Ann Agric Environ Med 1996, 3, 127-130. 55. Spiewak R, Moed H, von Blomberg BME, Bruynzeel DP, Scheper RJ, Gibbs S, Rustemeyer T: Allergic contact dermatitis to nickel: Modifi ed in vitro test protocols for better detection of allergen-specifi c response. Contact Dermatitis 2007, 56, 63-69. 56. Spiewak R, Skórska C, Dutkiewicz J: Work-related allergic skin symptoms among cattle and swine breeders. Allergy 2000, 55 (Suppl. 63), 155. 57. Spiewak R, Skórska C, Dutkiewicz J: Work-related skin symptoms among Polish farmers exposed to plant dust. Contact Dermatitis 2000, 42 (Suppl. 2), 62-63. 58. Spiewak R, Skórska C, Dutkiewicz J: Occupational airborne contact dermatitis caused by thyme dust. Contact Dermatitis 2001, 44, 235-239. 59. Spiewak R, Skórska C, Góra A, Horoch A, Dutkiewicz J: Young farmers with cellular reactivity to airborne microbes suffer more frequently from work-related skin symptoms and allergic dermatitis. Ann Agric Environ Med 2001, 8, 255-259. 60. Spiewak R, Skórska C, Prazmo Z, Dutkiewicz J: Bacterial endotoxin associated with pollen as a potential factor aggravating pollinosis. Ann Agric Environ Med 1996, 3, 57-59. 61. Taguchi T, Abe S, Nakano K, Matsui Y, Sohmura Y: Synergistic enhancement of the antitumor activity of recombinant human TNF-alpha by recombinant human IFN-gamma. Cancer Detect Prev 1988, 12, 105- 114. 62. Teixeira LK, Fonseca BP, Barboza BA, Viola JP: The role of interferon- gamma on immune and allergic responses. Mem Inst Oswaldo Cruz 2005, 100 (Suppl. 1), 137-144. 63. Van Horssen R, Ten Hagen TL, Eggermont AM: TNF-α in cancer treatment: molecular insights, antitumor effects, and clinical utility. Oncologist 2006, 11, 397-408. 64. Von Essen S, Fryzek J, Nowakowski B, Wampler M: Respiratory symptoms and farming practices in farmers associated with an acute febrile illness after organic dust exposure. Chest 1999, 116, 1452-1458.

© Radoslaw Spiewak (contact).
This page is part of the www.RadoslawSpiewak.net website.
Document created: 25 June 2008, last updated: 2 July 2008.