Capacity of CD34+ progenitor-derived dendritic cells to distinguish between sensitizers and irritants

In an attempt to develop an in vitro test to identify contact sensitizers, mostly dendritic cells (DCs) derived from monocytes (Mo-DC) have been used. Less is known about the potency of DC derived from CD34+ progenitors (CD34-DC) for in vitro allergen testing. CD34+ progenitor derived DC were exposed to nine well-known allergens (one weak, three moderate and five strong allergens) and two irritants. Surface marker expression (CD86, CD83 and HLA-DR) and cytokine production (IL-6, IL-12 and TNF-alpha) were analyzed after 24 h exposure to these chemicals. All allergens tested induced a significant increase in at least one of the DC surface markers. In contrast, none of the irritants tested were able to significantly upregulate membrane marker expression in exposed DC. The level of upregulation of CD86, CD83 and HLA-DR was dependent on the nature and concentration of the chemical, but not on the classification of the allergen. Changes in cytokine production (IL-6, IL-12 and TNF-alpha) were not consistently related to exposure to an allergen. Based on these results, we conclude that the in vitro test using CD34-DC has the capacity to distinguish between allergens and irritants based on altered phenotypic characteristics.     

Differential modulation of CXCR4 and CD40 protein levels by skin sensitizers and irritants in the FSDC cell line

The development of non-animal methods for skin sensitization testing is an urgent challenge. Some of the most promising in vitro approaches are based on the analysis of phenotypical and functional modifications induced by sensitizers in dendritic cell models. In this work, we evaluated, for the first time, a fetal skin-derived dendritic cell line (FSDC) as a model to discriminate between sensitizers and irritants, through analysis of their effects on CD40 and CXCR4 protein expression. The chemicals concentrations were chosen based on a slight cytotoxicity effect (up to 15%). Protein levels were evaluated by Western blot and immunocytochemistry, after stimulation with the skin sensitizers 2,4-dinitrofluorobenzene (DNFB), 1,4-phenylenediamine (PPD) and nickel sulphate (NiSO(4)), the non-sensitizer 2,4-dichloronitrobenzene (DCNB), and the irritants sodium dodecyl sulphate (SDS) and benzalkonium chloride (BC). All sensitizers tested increased CD40 and CXCR4 levels. In contrast, irritants decreased both proteins levels, with a more pronounced effect on CXCR4. In agreement with these results, dendritic cells derived from human peripheral blood monocytes-derived dendritic cells (MoDC) showed a similar response pattern to the skin sensitizer and irritant tested, PPD and SDS, respectively. In conclusion, evaluation of CD40 and CXCR4 proteins in chemical-treated FSDC may represent a useful tool in a future in vitro test for sensitizing assessment.     

The cytokine-dependent MUTZ-3 cell line as an in vitro model for the screening of contact sensitizers

Langerhans cells (LC) are key mediators of contact allergenicity in the skin. However, no in vitro methods exist which are based on the activation process of LC to predict the sensitization potential of chemicals. In this study, we have evaluated the performances of MUTZ-3, a cytokine-dependent human monocytic cell line, in its response to sensitizers. First, we compared undifferentiated MUTZ-3 cells with several standard human cells such as THP-1, KG-1, HL-60, K-562, and U-937 in their response to the strong sensitizer DNCB and the irritant SDS by monitoring the expression levels of HLA-DR, CD54, and CD86 by flow cytometry. Only MUTZ-3 and THP-1 cells show a strong and specific response to sensitizer, while other cell lines showed very variable responses. Then, we tested MUTZ-3 cells against a wider panel of sensitizers and irritants on a broader spectrum of cell surface markers (HLA-DR, CD40, CD54, CD80, CD86, B7-H1, B7-H2, B7-DC). Of these markers, CD86 proved to be the most reliable since it detected all sensitizers, including benzocaine, a classical false negative in local lymph node assay (LLNA) but not irritants. We confirmed the MUTZ-3 response to DNCB by real-time PCR analysis. Taken together, our data suggest that undifferentiated MUTZ-3 cells may represent a valuable in vitro model for the screening of potential sensitizers.     

Evaluation of CD86 expression and MHC class II molecule internalization in THP-1 human monocyte cells as predictive endpoints for contact sensitizers

The aim of this study was to explore the usefulness of a human monocyte cell line in the development of in vitro models for predictive testing of contact sensitizers. Several studies have shown that contact sensitizers induce CD86 expression and enhanced internalization of MHC class II molecules in dendritic cells (DCs). We used THP-1, a human monocyte cell line, as a replacement for DCs for evaluation of these phenotypical alterations as predictive endpoints for contact sensitizers. Known sensitizers and irritants were evaluated. After 24-h exposure to samples, the expression of CD86 on THP-1 cells was measured by flow cytometry. Sensitizers such as dinitrochlorobenzene (DNCB), 2-mercaptobenzothiazole (MBT), eugenol, p-phenylenediamine (PPDA) and ammonium tetrachloroplatinate (Pt) enhanced CD86 expression on THP-1 cells, while nickel sulfate, cobalt sulfate and irritants such as methylsalicylate (MS), sodium dodecyl sulfate (SDS) and dimethyl sulfoxide (DMSO) did not augment CD86 expression. A synergistic effect was observed when DNCB and IFN- were added simultaneously to a culture of THP-1 cells. Furthermore, internalization of MHC class II molecules was observed when the cells were treated with some of sensitizers for 2 h. The inducing effects of chemicals on the two phenotypical alterations were the same. These results suggest that these test systems can be used to predict contact-sensitizing ability of chemicals as an in vitro sensitization assay.     

Identification of contact and respiratory sensitizers according to IL-4 receptor α expression and IL-2 production

Identification of allergenic chemicals is an important occupational safety issue. While several methods exist to identify contact sensitizers, there is currently no validated model to predict the potential of chemicals to act as respiratory sensitizers. Previously, we reported that cytometry analysis of the local immune responses induced in mice dermally exposed to the respiratory sensitizer trimellitic anhydride (TMA 10%) and contact sensitizer dinitrochlorobenzene (DNCB 1%) could identify divergent expression of several immune parameters. The present study confirms, first, that IgE-positive B cells, MHC class II molecules, interleukin (IL)-2, IL-4 and IL-4Rα can differentiate the allergic reactions caused by high doses of strong respiratory (TMA, phthalic anhydride and toluene diisocyanate) and contact sensitizers (DNCB, dinitrofluorobenzene and oxazolone). The second part of the study was designed to test the robustness of these markers when classing the weakly immunogenic chemicals most often encountered. Six respiratory allergens, including TMA (2.5%), five contact allergens, including DNCB (0.25%), and two irritants were compared at doses of equivalent immunogenicity. The results indicated that IL-4Rα and IL-2 can be reliably used to discriminate sensitizers. Respiratory sensitizers induced markedly higher IL-4Rα levels than contact allergens, while irritants had no effect on this parameter. Inversely, contact allergens tended to induce higher percentages of IL-2⁺CD8⁺ cells than respiratory allergens. In contrast, the markers MHC-II, IgE and IL-4 were not able to classify chemicals with low immunogenic potential. In conclusion, IL-4Rα and IL-2 have the potential to be used in classifying a variety of chemical allergens.     

Intracellular expression of cytokines and granzyme B in auricular lymph nodes draining skin exposed to irritants and sensitizers

The murine local lymph node assay (LLNA) has been extensively utilized to evaluate sensitizing chemicals. However, there have been some concerns that its use to discriminate between classes of chemicals is minimal. It is thus desirable to identify better or alternative immune endpoints with in LLNA itself. Here, we evaluated the protein and/or mRNA levels of cytokines and granzyme B (GzmB), a cytotoxic lymphocyte product, to discriminate between sensitizers and irritants and to characterize the chemical sensitizers when used as supplemental indicators in LLNA endpoints. For this, CBA/N mice were topically treated daily with a well-known chemical sensitizer such as a strong contact sensitizer 1-chloro-2,4-dinitrobenzene (DNCB), a skin contact sensitizer 2-phenyl-4-ethoxymethylene-5-oxazolone (OXA), and a skin or respiratory sensitizer toluene 2,4-diisocyanate (TDI), and the non-sensitizing irritants, croton oil (CRO) and nonanoic acid (NA), for 3 consecutive days. The protein and/or mRNA levels in auricular lymph nodes draining the ear skin were then analyzed by real-time RT-PCR and immunoassay. The sensitizers, but not the irritants, evoked pronounced interleukin (IL)-2, IL-3 and IL-4 or interferon (IFN)-gamma. Significantly, different sensitizers evoked different cytokine patterns of IL-4 and IFN-gamma, as DNCB strongly up-regulated both IFN-gamma and IL-4, OXA up-regulated IFN-gamma strongly but IL-4 weakly, and TDI up-regulated IL-4 strongly but IFN-gamma weakly. The sensitizers also strongly up-regulated GzmB mRNA, while the irritants had a much weaker effect. Thus, these cytokines and GzmB mRNA may be useful as additional endpoints for discriminating between irritants and sensitizers or contact and respiratory sensitizers in the LLNA.     

Langerhans cells and immature dendritic cells as model systems for screening of skin sensitizers.

Langerhans cells are the most potent antigen-presenting cells in the skin and play a critical role in the induction of contact allergy. Research on the phenotypical and functional changes of LCs occurring after application of skin sensitizers indicated their use as an in vitro model for the screening of chemicals. In the present investigations, LCs from human skin explants served as the test system. The application of this cell system has been aggravated by the difficulty in isolating sufficient numbers of live LCs from skin. This disadvantage was overcome by the culture of immature dendritic cells from peripheral mononuclear blood cells. These cells can serve as a replacement for LCs as they bind haptens and show phenotypical and functional changes similar to LCs. The sensitizers NiSO(4), dinitrochlorobenzene, 2,4,6-trinitrobenzene sulfonic acid, alpha-hexylcinnamaldehyde and eugenol were applied. Both the expression of surface markers and the induction of intracellular interleukin-1 beta (IL-1 beta) were analyzed. No clear-cut results could be established for intracellular cytokine production, only NiSO(4) induced a remarkable number of IL-1 beta-positive cells. However, all skin sensitizers caused an up-regulation of the co-stimulatory molecule CD86, of intercellular adhesion molecule CD54 and of the HLA-DR antigen. The irritant sodium dodecyl sulfate (SDS) and the vehicle dimethyl sulfoxide (DMSO) had no effect.     

NCTC 2544 and IL-18 production: A tool for the identification of contact allergens

Progress in understanding the mechanisms of skin sensitization, provides us with the opportunity to develop in vitro tests as an alternative to in vivo sensitization testing.Keratinocytes play a key role in all phases of skin sensitization. We have recently identified interleukin-18 (IL-18) production in keratinocyte as a potentially useful endpoint for determination of contact sensitization potential of low molecular weight chemicals. The aim of the present article is to further exploit the performance of the NCTC 2544 assay.NCTC 2544 is a commercially available skin epithelial-like cell line originating from normal human skin, which posses a good expression of cytochrome P450-dependent enzymatic activities. Cells were exposed to contact allergens (2-bromo-2-bromomethyl glutaronitrile, cinnamaldehyde, citral, diethylmaleate, dinitrochlorobenzene, glyoxal, 2-mercaptobenzothiazole, nickel sulfate, 4-nitrobenzylbromide, oxazolone, penicillin G, resorcinol, tetramethylthiuram disulfide), to pre- pro-haptens (cinnamyl alcohol, eugenol, isoeugenol, p-phenylediamine), to respiratory allergens (ammonium hexachloroplatinate, diphenylmethane diisocyanate, glutaraldehyde, hexamethylenediisocyanate, maleic anhydride, trimellitic anhydride) and to irritants (benzaldehyde, cholorobenzene, diethylphtalate, hydrobenzoic acid, lactic acid, octanoic acid, phenol, salicylic acid, sodium lauryl sulphate, sulfamic acid). Cell associated IL-18 was evaluated 24 later by ELISA. At not-cytotoxic concentrations (cell viability higher of 80%, as assessed by MTT reduction assay), all contact sensitizers, including pre-pro-haptens, induced a dose-related increase in IL-18, whereas both irritants, with the exception of sulfamic acid, and respiratory allergens failed. A total of 33 chemicals were tested, with an overall accuracy of 97%.Overall, results obtained indicated that cell-associated IL-18 might provide an in vitro tool for identification and discrimination of contact vs. respiratory allergens and/or irritants.     

Chemicals with weak skin sensitizing properties can be identified using low-density microarrays on immature dendritic cells

A critical step in the induction of allergic contact dermatitis is the interaction of haptens with immature dendritic cells (iDC) leading to their activation. Therefore iDC appear as suitable targets for the evaluation of the sensitizing properties of haptens with the aim of developing in vitro toxicologic methods. Here, using a low-density cDNA-array, we analyzed the expression of 165 genes related to dendritic cell biology in human iDC following a 24h incubation with four haptens representative of strong (DNBS), moderate (isoeugenol) and weak (eugenol, hydroxycitronellal) contact sensitizers and with one irritant sodium dodecyl sulphate (SDS). Results show that 21/165 iDC genes were significantly modulated by hapten treatment. Some genes were preferentially modulated by a given chemical. Thus, DNBS, isoeugenol, eugenol and hydroxycitronellal consistently modulated CCR5, CCL27, CCL2 and CCR7, respectively, whereas the CXCL10 gene was regulated by SDS. When subjected to principal component analysis, the 21 target genes fell into four groups associated with a particular type of chemical endowed with distinct sensitizing or irritant properties. Thus, gene profiling of iDC using low-density microarray allows, for screening of chemicals, the indentification of weak haptens with potential skin sensitizing properties. These results suggest that gene profiling of iDC using low-density microarrays may be useful to identify chemicals with weak skin sensitizing properties.     

CXCL8 secretion by dendritic cells predicts contact allergens from irritants.

Monocyte-derived dendritic cell functions have been explored for identification of contact allergens in vitro. Current methods, including measurement of changes in cell surface marker expression (e.g. CD83, CD86) do not provide a sensitive method for detecting the sensitising potential of a chemical. In this study, we investigated whether chemokine production by monocyte-derived dendritic cells is increased upon maturation and whether chemokine production can provide methodology for the detection of allergens. Monocyte-derived dendritic cells were exposed to allergens (nickel sulphate, cobalt chloride, palladium chloride, copper sulphate, chrome-(III)-chloride, potassium dichromate, p-phenylenediamine and dinitrochlorobenzene) and irritants (sodium dodecyl sulphate, dimethylsulphoxide, benzalkoniumchloride and propane-1-ol). CD83 and CD86 expression was analysed by flow cytometry and chemokine production (CXCL8, CCL5, CCL17, CCL18, CCL19, CCL20, CCL22) was determined by ELISA. Significant up regulation of CD83 and CD86 expression could only be induced by three out of seven and five out of seven allergens, respectively. In contrast, CXCL8 production was significantly increased after stimulation with all allergens tested, whereas irritant exposure led to decreased CXCL8 production. All other chemokines tested, failed in identifying contact allergens. In conclusion, CXCL8 production, next to CD83 and CD86 up regulation, by monocyte-derived dendritic cells provides a promising in vitro tool for discrimination between allergens and irritants.     

Use of IL-18 production in a human keratinocyte cell line to discriminate contact sensitizers from irritants and low molecular weight respiratory allergens

Assessment of allergenic potential of chemicals is performed using animal models, such as the murine local lymph node assay, which does not distinguish between respiratory and contact allergens. Progress in understanding the mechanisms of skin sensitization, provides us with the opportunity to develop in vitro tests as an alternative to in vivo sensitization testing.The aim of the present study was to evaluate the possibility to use intracellular interleukin-18 (IL-18) production to assess in vitro the contact sensitization potential of low molecular weight chemicals. The human keratinocyte cell line NCTC2455 was used. Cells were exposed to contact allergens (cinnamaldehyde, dinitrochlorobenzene, glyoxal, isoeugenol, p-phenylediamine, resorcinol, tetramethylthiuram disulfide, 2-mercaptobenzothiazole, 4-nitrobenzylbromide), to proaptens (cinnamyl alcohol, eugenol), to respiratory allergens (diphenylmethane diisocyanate, trimellitic anhydride, ammonium hexachloroplatinate) and to irritants (sodium lauryl sulphate, salicylic acid, phenol). Cell associated IL-18 were evaluated 24 later. At not cytotoxic concentrations (cell viability higher of 75%, as assessed by MTT reduction assay), all contact sensitizers, including proaptens, induced a dose-related increase in IL-18, whereas both irritants and respiratory failed. Similar results were also obtained using primary human keratinocytes. Results were reproducible, and the method could be transferred to another laboratory, suggesting the potential use of the test in immunotoxicity testing strategies. Overall, results obtained indicated that cell-associated IL-18 may provide an in vitro tool for identification and discrimination of contact versus respiratory allergens and/or irritants.     

Analysis of interleukin-1alpha (IL-1alpha) and interleukin-8 (IL-8) expression and release in in vitro reconstructed human epidermis for the prediction of in vivo skin irritation and/or sensitization.

In the present study, reconstructed human epidermis (RHE) was used as an in vitro model to discriminate 1-chloro-2,4-dinitrobenzene (DNCB), nickel sulfate (NiSO(4)), oxazolone (OXA), 2,4-dinitrofluorobenzene (DNFB) and 2,4,6-trinitrobenzenesulfonic acid (TNBS) as skin sensitizers from benzalkonium chloride (BC), benzoic acid (BA) and sodium lauryl sulfate (SLS) as skin irritants. Our criteria were (a) the differential IL-1alpha and IL-8 synthesis and release (b) cytotoxicity assessment by MTT assay. When the RHE are topically treated with the sensitizers, very low levels of extra- and intracellular IL-1alpha are observed although they induce significant cytotoxicity. In contrast, they exhibit a sharp maximum of IL-8 release. In the presence of the tested irritants, we observe the inverse cytokine release profile, although they induce dose-dependent cytotoxicity profiles similar to those observed with the sensitizers. Finally, IL-1alpha mRNA upregulation is observed after topical application of both sensitizers and irritants, but only the latter significantly increase extracellular IL-1alpha. In conclusion, our results suggest that the associated determination of IL-8, with IL-1alpha, and MTT conversion are at least necessary to discriminate and classify, in a single assay, irritant and sensitizing agents and represent a potential in vitro alternative to two classical in vivo assays.     

Characterizing the immunological effects of oral healthcare ingredients using an in vitro reconstructed human epithelial model

Oral healthcare products are well tolerated and while adverse occurrences are rare there is still a need to explore the interaction between these products and the oral mucosa. This study assessed the effects of oral healthcare ingredients: sodium lauryl sulphate (SLS), a detergent; cinnamic aldehyde (CA), a flavouring agent; and cetylpyridinium chloride (CPC), an antiseptic, using a reconstructed human oral mucosal model (OMM). Differential release of inflammatory cytokines IL-1α, IL-8 and cytotoxicity was compared with other known irritants and sensitizers to identify a signature response profile that could be associated with oral mucosal irritation.Response profiles differed with irritants being more cytotoxic. CA and control sensitizers nickel sulphate (NiSO4) and 1-chloro-2,4-dinitrochlorobenzene (DNCB) released lower levels of IL-1α than CPC and control irritant benzalkonium chloride (BC), whereas the opposite was observed for IL-8. Significant levels of IL-8 and IL-1α were released with 5–15 mg/ml (0.5–1.5% w/v) SLS. Quantitative PCR indicated that cytokine release at lower SLS concentrations is not entirely due to cell necrosis but in part due to de novo synthesis. These findings suggest that the OMM can be used to predict oral irritation thus making it a potentially valuable model for screening new oral healthcare ingredients prior to clinical release.     

Contact allergens and irritants show discrete differences in the activation of human monocyte-derived dendritic cells: consequences for in vitro detection of contact allergens

In recent years test systems have been described that may be applied routinely to discriminate between contact allergens and irritants in vitro. Using human monocyte-derived dendritic cells (MoDC), this study was designed to refine the settings of a potential routine screening protocol for contact allergens and to investigate the so far poorly defined concentration dependency of contact allergen-specific effects. MoDC were generated by 6 days of culture in the presence of IL-4 and GM-CSF and were then cultured for 24 or 48 h in medium with lipopolysaccharide (LPS), contact allergens [picrylsulphonic acid (TNBS), 1-chloro-2,4-dinitrobenzene (DNCB)] or irritants [sodium dodecyl sulphate (SDS), benzalkonium chloride (BAC)] that were free of detectable endotoxin contamination. The induction of CD86 and HLA-DR expression was quantified by flow cytometry as markers for MoDC activation. LPS activation upregulated CD86 about 20-fold and HLA-DR expression about 4-fold. Compared to LPS, contact allergens had weaker effects. TNBS and DNCB induced activation marker upregulation starting slightly below the cytotoxic concentration and increasing in a dose-dependent manner. However, at partially cytotoxic concentrations, irritants also induced CD86 and HLA-DR expression, as confirmed by flow cytometry and quantitative RT-PCR. Both SDS and BAC induced activation marker expression on surviving MoDC, when more than 50% of the MoDC population had been killed by the treatment. Consequently, routine testing of unknown substances would need to quantify activation marker expression as well as cytotoxicity in parallel. In the concentration range around the lowest cytotoxic concentration, the assay may be able to discriminate between contact allergens and irritants.     

Modulation of phenotype, cytokine production and stimulatory function of CD34+-derived DC by NiCl(2) and SDS.

One of the most promising alternatives to identify the sensitizing potency of new products is the in vitro culture of human dendritic cells (DC). In vivo, dendritic cells present in the skin are highly specialized antigen-presenting cells (APC) of the immune system, which play a crucial role in the induction of allergic reactions. The DC produce specific cytokines and upregulate specific co-stimulatory molecules in addition to the antigen-MHC complex in order to promote an optimal T-cell activation. The aim of our study is to assess the phenotype, cytokine production and autologous T-cell stimulatory capacity of the in vitro CD34+-derived dendritic cells after 24 hours of incubation with the metal allergen NiCl(2) (100-300 microM) and the irritant sodium dodecyl sulfate (SDS; 0.01%), in order to find a sensitive endpoint to discriminate between sensitizers and irritants. After exposure to Ni, a significant increase in the number of CD83+ and CD86+ cells was noticed. The intensity of CD86 as well as the intensity of the HLA-DR molecule on the DC also showed a significant increase. The expression of the co-stimulatory molecule CD80 was not changed after exposure. SDS was not able to increase the expression of any of the analysed markers. The production of IL-6 increased significantly after exposure of dendritic cells to Ni, but not after SDS exposure. Results on tumor necrosis factor-alpha (TNF-alpha) production are somewhat equivocal. Although not statistically significant, TNF-alpha was upregulated in one out of three experiments after 48 hours of exposure to the Ni allergen, but increases were also noticed after exposure to SDS (two out of three experiments). Both exposure to Ni and SDS caused an upregulation (not significant) in the IL-12 production by DC, but the production was higher in Ni-exposed DC compared to SDS-exposed cells. In none of the exposed DC cultures was it possible to detect IL-1 beta. The antigen-presenting capacity of the DC in autologous MLR could not be demonstrated. Nevertheless, T-cell proliferation after DC stimulation was noticed in allogenic MLR.     

Phenotypic alterations and cytokine production in THP-1 cells in response to allergens.

In the induction phase of allergic contact hypersensitivity, dendritic cells (DCs), including Langerhans cells (LCs) present in epidermis, can trigger an efficient T cell response once they have matured in response to an allergen. Upon maturation, DCs have been shown to induce expression of several surface molecules and the up-regulation of cytokine production. We have previously shown that THP-1 cells, human acute monocytic leukemia cell line, can discriminate between allergens and irritants by measuring expression of surface markers, CD86 and CD54, following chemical exposure. At the same time, we have also reported that augmented expression of HLA and CD80, and production of IL-1beta were up-regulated in THP-1 cells when treated with an allergen, 2,4-dinitrochlorobenzene (DNCB). In the present study, we first evaluated whether THP-1 cells induced the phenotypic changes and the production of cytokines, which are observed in the process of DC maturation, when treated with two known allergens, DNCB and nickel sulfate (NiSO(4)), and one irritant (sodium lauryl sulfate (SLS)). Exposure to DNCB and NiSO(4) induced significant augmentation of CD40 and CD83 expression as well as CD86 and CD54. Also, TNF-alpha and IL-8 secretion were markedly induced by DNCB and NiSO(4) in a dose-dependent manner. In addition, DNCB and NiSO(4) augmented CD1a expression and production of IL-6, respectively. On the contrary, SLS did not change any of these markers. We then evaluated a series of chemicals, including six known allergens (e.g., hydroquinone (HQ)) and two non-allergens (e.g., methyl paraben (MP)), in order to investigate the potential increase of CD86, CD54, CD40, and CD83 expression on THP-1 cells, and production of TNF-alpha and IL-8. Indeed, all tested allergens, except eugenol (EU), caused significant increased changes in at least four of the analyzed six markers, while non-allergens did not induce any changes. EU significantly augmented CD86, CD54 and CD40 expression. These results revealed that the wide variety of responses to allergens in THP-1 cells may emulate allergen-induced maturation processes of DCs. It is suggested that THP-1 cells, which could develop several DC-like properties, are suitable for identifying sensitizing potential of chemicals.