Cytokine profiles,apoptosis and pathology of experimental Pasteurella multocida serotype A1 infection in mice

Mice were experimentally infected with Pasteurella multocida serotype A1 to study the cytokine profiles, host cell apoptosis and sequential pathology at different hours of post-infection. Infected mice were dull, anorectic and depressed. A transient leukocytopenia followed by progressive leukocytosis was observed in the course of infection. Serum cytokine profiles showed significantly (P < 0.01) higher amount of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and mouse KC) in the infected mice when compared to control mice. The circulating lymphocytes were apoptotic on annexin V staining. Apoptotic nuclei were detected in splenocytes, hepatocytes and infiltrating leukocytes of the lungs on TUNEL staining. The lungs were grossly congested and hemorrhagic, and showed infiltration with polymorphonuclear cells at early and mononuclear cells in the late hours of infection. Alveolar epithelia, inter-alveolar septa and capillary endothelium of the lungs showed ultrastructural changes. Liver had degenerative changes in histological and ultrathin sections.     

Cellular and humoral immune responses during intrathoracic paracoccidioidomycosis in BALB/c mice

Paracoccidioidomycosis is a chronic infection that primarily affects the lungs. Here we investigated cellular and humoral immune responses after intrathoracic Paracoccidioides brasiliensis infection in BALB/c mice. P. brasiliensis-colony-forming units (CFUs), fungal DNA and granulomas in lungs increased progressively, peaking at day 90 postinfection (p.i.). IFN-γ production was highest on day 15 p.i., declining thereafter. The kinetics of the NO production was similar to that described for IFN-γ. In contrast, IL-10 increased from day 45 p.i. reaching a peak at day 90. Levels of serum IgG1 were higher than IgG2a between days 30 and 90 p.i. 30% of mice died by day 90 p.i. These data indicate that infection with P. brasiliensis by the intrathoracic route shows high IFN-γ and NO production at day 15 p.i., unable to control multiplication of fungi, which appears to be associated with a progressive increase in IL-10 and in the number and complexity of granulomas.     

Bovine herpesvirus type 1 infection of bovine bronchial epithelial cells increases neutrophil adhesion and activation

Respiratory infection of cattle with bovine herpesvirus type 1 (BHV-1) predisposes cattle to secondary pneumonia with Mannheimia haemolytica as part of the bovine respiratory disease complex (BRD). One cell type that has received limited investigation for its role in the inflammation that accompanies BRD is the respiratory epithelial cell. In the present study we investigated mechanisms by which BHV-1 infection of respiratory epithelial cells contributes to the recruitment and activation of bovine polymorphonuclear neutrophils (PMNs) in vitro. Primary cultures of bovine bronchial epithelial (BBE) cells were infected with BHV-1 and assessed for cytokine expression by real-time PCR. We found that BHV-1 infection elicits a rapid IL-1, IL-8 and TNF-α mRNA response by BBE cells. Bovine PMNs exhibited greater adherence to BHV-1 infected BBE cells than uninfected cells. The increased adherence was significantly reduced by the addition of an anti-IL-1β antibody or human soluble TNF-α receptor (sTNF-αR). Pre-incubation of bovine PMNs with conditioned media from BHV-1 infected BBE cells increased PMN migration, which was inhibited by addition of an anti-IL-1β antibody, sTNF-αR, or an IL-8 peptide inhibitor. Conditioned media from BHV-1 infected BBE cells activated bovine PMNs in vitro as demonstrated by PMN shape change, production of reactive oxygen species and degranulation. PMNs also exhibited increased LFA-1 expression and susceptibility to M. haemolytica LKT following incubation with BHV-1 infected BBE cell conditioned media. Our results suggest that BHV-1 infection of BBE cells triggers cytokine expression that contributes to the recruitment and activation of neutrophils, and amplifies the detrimental effects of M. haemolytica LKT.     

Systemic cytokine profiles of mice vaccinated with naked DNAs encoding six open reading frame antigens of porcine circovirus type 2 (PCV2)

The objective of this study was to characterize the murine immune response to vaccination with DNAs encoding each of six porcine circovirus type 2 (PCV2) open reading frames (ORFs). After intramuscular vaccination with the naked DNAs, blood was taken on days post-infection (DPI) 7 and 35 and subjected to Bio-Plex cytokine assays. ORF3 elicited high levels of the pro-inflammatory cytokine TNF-α (P < 0.001) and decreased IL-12 levels (P < 0.001) on DPI 7, and was lethal for nine of the 15 vaccinated mice, which died on DPIs 4, 6, 9, and 10. The remaining six mice showed general prostration but then recovered. The clinical signs correlated with the systemic TNF-α and IL-12 levels. ORF1 vaccination elevated T-helper (Th)1 (IFN-γ; P < 0.001) and Th2 (IL-13; P < 0.05) cytokine levels on DPI 35, while ORF2 markedly elevated the expression of the humoral immunity- and Th-2-related cytokine IL-10 (P < 0.001) on DPI 35. These observations provide insights into the immune responses generated by each PCV2 ORF.     

Role of nitric oxide production in dairy cows naturally infected with Mycobacterium avium subsp. paratuberculosis

Nitric oxide (NO) is a crucial mediator in host defense and is one of the major killing mechanisms within macrophages. Its induction is highly affected by the types of cytokines and the infectious agents present. In the current study, NO production was evaluated after in vitro infection of unfractionated peripheral blood mononuclear cells (PBMCs) with Mycobacterium avium subsp. paratuberculosis (MAP) after 8 h, 3 and 6 days of culture for cows in different stages of disease. In addition, the effects of in vitro exposure to inhibitory cytokines such as interleukin-10 (IL-10) and transforming growth factor β (TGF-β) as well as the pro-inflammatory cytokine IFN-γ were correlated with the level of NO production. Nitric oxide production was consistently higher in cell cultures from subclinically infected animals at all time points. An upregulation of NO production was demonstrated in unfractionated cell cultures from healthy control cows after exposure to MAP infection as compared to noninfected cell cultures. A similar increase in NO due to the addition of MAP to cell cultures was also noted for clinically infected cows. NO level among subclinically infected cattle was greater at all time points tested and was further boosted with the combination of both in vitro MAP infection and IFN-γ stimulation. Alternatively, nonspecific stimulation with LPS from Escherichia coli O111:B4-W resulted in an upregulation of NO production in all infected groups at 3 and 6 days after in vitro infection. Finally, the in vitro exposure to inhibitory cytokines such as IL-10 and TGF-β prior to MAP infection or LPS stimulation resulted in the downregulation of this inflammatory mediator (NO) in all experimental groups at all time points. In summary, a higher level of NO production was associated with cows in the subclinical stage of MAP infection. As well, the results demonstrated an increase in NO production upon infection with MAP and in the presence of exogenous IFN-γ. Finally, the results suggest an important role of IL-10 and TGF-β on the profile of NO production which may explain the low NO production in MAP clinically infected cows.     

Neospora caninum infection during early pregnancy in cattle: how the isolate influences infection dynamics,clinical outcome and peripheral and local immune responses

This work studies the influence of Neospora caninum intra-species diversity on abortion outcome, infection dynamics in terms of parasite dissemination and peripheral-local immune responses in pregnant cattle. Animals were intravenously inoculated at day 70 of pregnancy with 10⁷ tachyzoites of two isolates showing marked differences in virulence in vitro and in pregnant mouse models: Nc-Spain7, a high virulence isolate, and Nc-Spain8, a low-to-moderate virulence isolate. After inoculation, pregnancy was monitored, and dams were culled when foetal death was detected. Foetal mortality occurred in all infected heifers between days 24 and 49 post-infection (pi), however, it was detected sooner in Nc-Spain7-infected animals (median day = 34) than those inoculated with Nc-Spain8 (median day = 41) with a trend towards significance (P < 0.11). Similar histological lesions were observed in placentomes and in most of the foetuses from the two infected groups. However, parasites were more frequently detected in the placenta and foetuses by PCR and in the foetal brain by immunohistochemistry in Nc-Spain7-infected animals. Specific antibodies were detected starting at day 13 post-infection in all infected cattle, with higher IgG levels in Nc-Spain7-infected group. IFN-γ and IL-4 profiles also varied between infected groups in PBMC stimulation assays. Infected animals showed significant increases in their cytokine mRNA levels (IFN-γ, IL-4, IL-10, IL-12p40 and TNF-α) in the caruncle at time of foetal death. Differences between the infected groups were also observed for cytokine profiles. These results demonstrate the influence of the N. caninum isolate on foetal death outcome, infection dynamics and immune responses in cattle.     

小鼠细胞因子实时定量PCR检测方法的建立及应用

采用荧光SYBR Green I建立小鼠细胞因子mRNA实时定量PCR的检测方法;并利用建立的实时定量PCR的检测方法时感染H5N1禽流感病毒的BALB/c小鼠不同时间采集的肺脏组织中几种重要致炎细胞因子及趋化因子mRNA表达水平进行了检测.对HSN1禽流感病毒感染的BALB/c小鼠肺脏细胞因子的检测具有高度的特异性,检测的灵敏度为10~1～10~2拷贝数.H5N1禽流感病毒感染BALB/c小鼠后,小鼠肺脏中IL-1β、IL-6、TNFα、MIG、IP-10、RANTES、MIF和HMGB1细胞因子mRNA表达水平与时照组小鼠相比均有明显差异.建立的实时定量PCR能在基因转录水平敏感和特异地反应细胞因子的表达水平,该技术在基础和临床免疫研究中,具有良好的应用价值.     

Local and systemic cytokine responses during larval penetration in cattle experimentally infested with Hypoderma lineatum (Diptera: Oestridae)

Local and systemic cytokine responses were studied in 3 groups of cattle, with 4 animals each, experimentally infested with Hypoderma lineatum (De Villers) first instars (L1). The first group was undergoing a primary infestation (G-1), the second group was undergoing a secondary infestation (G-2) and the third group was infested for their third consecutive year (G-3). Cattle were infested with 25 L1 deposited on the skin. Blood and skin samples were taken at 0, 6, 12, 48, 96 and 144 h post-infestation (h.p.i.). Interleukin 10 (IL-10), IL-4 and interferon gamma (IFN-γ) production was studied by immunohistochemistry and sandwich ELISAs. IL-4⁺ cells showed a significant increase at 6 h.p.i. in both reinfested groups (G-2 and G-3) when compared with G-1. In all groups the number of IL-4⁺ cells decreased significantly at 48 h.p.i. IL-10⁺ cells increased in G-1 at 6 and 48 h.p.i., whereas in both reinfested groups increased at 12 h.p.i. with a peak at 48 h.p.i. IFN-γ⁺ cells showed a significant increment at 6 h.p.i. in all groups, followed by a rapid descent at 12 (G-1 and G-2) and 48 h.p.i. (G-3). Penetration of the skin by H. lineatum did not have any significant effect on IFN-γ serum concentrations and, except for IL-10 there were no correlation between local production and serum concentrations of cytokines. The increase of both Th1 (IFN-γ) and Th2-type cytokines (IL-4 and IL-10) indicates that bovine T-cell response during the first phases of the infestation by H. lineatum is apparently a Th0 response.     

Effects of recombinant interferon-gamma on cytokine secretion from monocyte-derived macrophages infected with Salmonella typhi

Salmonella typhi (S. typhi) is an important pathogen which causes typhoid fever. The cytokines released from the macrophages, playing a role in the host defense against Salmonella infection, are crucial in the defense against the infection. IFN-γ provides a protection against Salmonella infection by developing macrophage activation in different mechanisms. This study was designed to investigate the effect of the recombinant IFN-γ (rIFN-γ) on the cytokines secreted from S. typhi stimulated macrophages. Macrophage isolation was done in the heparinized blood samples obtained from healthy people, and following the priming with rIFN-γ for 72 h the cells were stimulated by S. typhi and then the cytokine levels in culture supernatants were determined by enzyme-linked immunosorbent assay. It was observed that rIFN-γ reversely increased the levels of IL-1, IL-2 the levels of which were decreased by S. typhi and that it increased TNF-α levels while suppressing the levels of antiinflammatory cytokines such as IL-10 and TGF-β the levels of which were increased by S. typhi. Consequently, rIFN was observed to increase protective Th1 response by affecting the secretion of cytokine during S. typhi infection and it was considered to be a good target especially to prevent and treat invasive Salmonella infections.     

Effects of Teladorsagia (Ostertagia) circumcincta infection on lambs selected for high fleece weight

The physiological processes leading to the expression of the resilient phenotype, which allow animals to maintain a relatively higher production level during infection, have been investigated in lambs from a closed flock selected for 40 generations for high fleece weight (HFW), but with higher FEC and worm burdens than their unselected control (C) flock run in parallel. After recovery from surgery to implant abomasal cannulae, eight parasite-naïve lambs from each flock were infected intraruminally at 4.5 months-of-age with 50,000 Teladorsagia circumcincta L3. Blood, abomasal fluid and faecal samples were collected daily for measurement of serum gastrin and pepsinogen concentrations, blood eosinophils, abomasal pH and FEC. Four lambs from each flock were euthanased on Day 8 post-infection and the other four on Day 28 post-infection. At necropsy, abomasal contents and tissues were collected for worm counts, abomasal lymph nodes and fundic tissue for cytokine gene expression and fundic tissue for histopathology. Expression of resilience appeared to be age-dependent as there were no significant differences in either FEC or worm burden between lambs from the two flocks, unlike older HFW lambs in a previous study. Abomasal secretion did not differ between flocks. Histopathological changes were typical of parasitism: inflammatory cells, mainly eosinophils and lymphocytes, were numerous in nodular areas and there were fewer TGF-α positive parietal cells, many of which were vacuolated. By Day 28 p.i., globule leucocytes were present. Mucosal thickness was significantly greater on Day 8 than Day 28 p.i. (p = 0.000) and in C than HFW lambs. There were fewer parietal cells on Day 28 than on Day 8 p.i. (p = 0.003) for pooled data. Circulating eosinophil counts increased moderately in both groups, significantly less in the HFW lambs. Fewer tissue and blood eosinophils in the HFW than C group on Day 8 p.i. were consistent with cytokine gene expression patterns, particularly lower IL-5 levels. Worm count decreased by 90% by Day 28 p.i., along with declining tissue eosinophil counts and IL-13 gene expression and increasing IL-10 and IL-4 gene expression. Food intake was depressed less in the HFW lambs, suggesting that maintenance of appetite could be an important aspect of the physiological basis for resilience. Although the resilient phenotype was not apparent at the younger age, lesser effects on food intake, differences in ALN cytokine profiles and lower blood and tissue eosinophil numbers in the HFW lambs may lead to the expression of resilience when older.     

IL-4受体阻断对小鼠急性感染肝片吸虫后肝脏单核细胞悬液中细胞因子的影响

本研究旨在探索肝片吸虫感染小鼠急性期肝脏单核细胞悬液中细胞因子表达模式及其原因。试验将小鼠分为4组,分别对感染抗体处置组、感染非抗体处置组、抗体处置非感染组和非抗体处置非感染组的肝脏单核细胞培养上清液中IL-4、IL-5、IL-13及IFN-γ进行测定;同时也对肝脏中IL-4及IL-12P40 mRNA水平进行荧光定量PCR检测。结果显示,IL-4和IL-5的表达模式相似。在非感染状态下,无论是否进行抗体处置,两者都处于较低表达水平。在感染状态下,两者在非抗体处置小鼠中的表达显著高于抗体处置组(P<0.05)。IL-13与IL-4及IL-5的表达差异在于感染并用抗体处置后,小鼠肝脏单核细胞中的IL-13仍有较高水平表达。IFN-γ的表达量在感染后有所增加,但在有无抗体处理间无显著差异(P>0.05)。mRNA检测结果显示,在非感染状态下,抗体处置后的IL-4 mRNA水平显著低于非抗体处置组(P<0.05)。感染后非抗体处置组小鼠中IL-4 mRNA水平极显著高于抗体处置组(P<0.01),同时也极显著高于非感染非抗体处置组(P<0.01)。IL-12P40 mRNA的水平在感染状态下,抗体处置组的IL-12P40 mRNA虽较非抗体处置组低,但无显著差异(P>0.05)。但感染后非抗体处置组的IL-12P40 mRNA水平均极显著高于感染组抗体处置和非抗体处置组(P<0.01)。本试验结果表明,IL-4Rα对肝片吸虫感染急性期IL-5和IL-4的表达极其重要,但对IL-13及IFN-γ的影响较小。     

In vitro effect of vitamin E on lectin-stimulated porcine peripheral blood mononuclear cells

In order to analyze the effect of vitamin E on Th1 and Th2 cytokine production, porcine peripheral blood mononuclear cells (PBMC) were isolated from healthy pigs (n = 8) and cultured with either 0, 10, 50, or 100 μM of vitamin E (α-tocopherol). PBMC were stimulated with PHA for either, 24 h to determine: (a) the concentration of tocopherol incorporated into the cell membrane, (b) cytokine production and (c) Th1 and Th2 regulators gene expression; or 72 h to determine the proliferation of PBMC. Vitamin E was incorporated into the PBMC in a dose dependent manner, giving as a result a high proliferation of cells irrespective of the dose of vitamin E used. Regarding cytokine production, vitamin E consistently decreases the mRNA expression and the percentage of cells producing IL-10. Vitamin E did not influence the production of IFN-γ but the lowest level of vitamin E (10 μM) was sufficient to maximally increase the proportion of cells producing IL-2, to diminish IL-4, and discreetly increase the mRNA expression of TBX21 vs. GATA3. In conclusion, our results revealed that vitamin E is able to suppress IL-10 production and to influence the production of IL-2, IL-4, and maybe TBX21. Vitamin E clearly has immunomodulatory effects, though further work in vivo to determine the physiological nature of these effects is warranted.     

Development and validation of cytokine quantitative, real time RT-PCR assays for characterization of Asian elephant immune responses

Infectious disease is an important factor in Asian elephant health and long-term species survival. In studying disease pathogenesis, it is important to consider not only the pathogen, but also the effectiveness of the host immune response. Currently, there is a paucity of information available on elephant immune function. Measurement of cytokine levels within clinical samples can provide valuable information regarding immune function during health and disease that may elucidate disease susceptibility. To develop tools for assessment of elephant immune function, Asian elephant partial mRNA sequences for interleukin (IL)-2, IL-4, IL-10, IL-12, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and β-actin were determined. Sequence information was then utilized to design elephant-specific primers and probes for quantitative, real time, RT-PCR assays for the measurement of cytokine mRNA. Greater than 300 bps of Asian elephant mRNA sequence were determined for each cytokine of interest. Consistent and reproducible, real time, RT-PCR assays with efficiencies of greater than 93% were also developed. Assay sensitivities ranged from less than 1 to 5000 DNA copies with the exception of IL-12, which had a sensitivity of 42,200 copies. Employment of molecular techniques utilizing mRNA-based detection systems, such as real time, RT-PCR, facilitate sensitive and specific cytokine detection and measurement in samples from species for which commercial reagents are not available. Future studies utilizing these techniques to compare elephant immune function during health and in the face of infection will be useful for characterizing the contribution of the elephant immune system to disease.     

Mucosal and systemic T cell response in mice intragastrically infected with Neospora caninum tachyzoites

The murine model has been widely used to study the host immune response to Neospora caninum. However, in most studies, the intraperitoneal route was preferentially used to establish infection. Here, C57BL/6 mice were infected with N. caninum tachyzoites by the intragastric route, as it more closely resembles the natural route of infection through the gastrointestinal tract. The elicited T-cell mediated immune response was evaluated in the intestinal epithelium and mesenteric lymph nodes (MLN). Early upon the parasitic challenge, IL-12 production by conventional and plasmacytoid dendritic cells was increased in MLN. Accordingly, increased proportions and numbers of TCRαβ⁺CD8⁺IFN-γ⁺ lymphocytes were detected, not only in the intestinal epithelium and MLN, but also in the spleen of the infected mice. In this organ, IFN-γ-producing TCRαβ⁺CD4⁺ T cells were also found to increase in the infected mice, however later than CD8⁺ T cells. Interestingly, splenic and MLN CD4⁺CD25⁺ T cells sorted from infected mice presented a suppressive activity on in vitro T cell proliferation and cytokine production above that of control counterparts. These results altogether indicate that, by producing IFN-γ, TCRαβ⁺CD8⁺ cells contribute for local and systemic host protection in the earliest days upon infection established through the gastrointestinal tract. Nevertheless, they also provide substantial evidence for a parasite-driven reinforcement of T regulatory cell function which may contribute for parasite persistence in the host and might represent an additional barrier to overcome towards effective vaccination.     

Therapeutic effect of anti-TNF-α antibody and levofloxacin (LVFX) in a mouse model of enterohemorrhagic Escherichia coli O157 infection

The ability of an anti-TNF-α antibody to confer protection against enterohaemorrhagic Escherichia coli (EHEC) O157 was investigated in germfree IQI mice. The use of an antibiotic levofloxacin (LVFX) alone or with the antibody was also studied. Protection included an increase in survival rate. Treatment with the anti-TNF-α antibody inhibited the histological signs associated with EHEC infection but did not prevent the colonization of EHEC or production of Shiga toxin (Stx). No clinical signs were observed and EHEC was completely eliminated in the mouse model receiving both anti-TNF-α antibody and LVFX. Anti-TNF-α antibody suppressed inflammatory cytokine response in the mouse kidney and brain by EHEC infection.     

Impact of heparin and short term anesthesia on the quantification of cytokines in laboratory mouse plasma

Background

Studies have reported that heparin may be unsuitable as an anticoagulant in human plasma samples when quantifying cytokines using multiplex bead array assays. For mouse samples, multiplex assays have been validated for serum and EDTA-plasma, but it remains to be elucidated whether heparin influences the quantification of cytokines, and if so – to what extent. Furthermore, laboratory mice are often anesthetized for blood sampling, which causes acute stress that may influence circulating cytokine concentrations and thus bias experimental results. The objectives of the present study were to identify whether specific cytokine concentrations varied between heparin-plasma, serum, and EDTA-plasma, and whether short isoflurane anesthesia would influence the concentrations of these cytokines in the circulation. Twenty-three acute phase and pro-inflammatory cytokines were quantified in matched serum, EDTA-plasma, and heparin-plasma samples from anesthetized and unanesthetized male NMRI mice using a multiplex assay. In addition, samples from unanesthetized mice were spiked with three levels of heparin.

Results

The concentrations of five out of 23 cytokines were significantly different between sample types, but only one cytokine (IL-17A) differed between heparin-plasma and serum. When further spiking the heparin-plasma with increasing concentrations of heparin, there was a significant effect on 11 cytokines, where the cytokine recovery could be correlated to the heparin concentration for ten of these cytokines. Anesthesia resulted in lower concentrations of G-CSF, but had no significant impact on the concentrations of the other 22 cytokines.

Conclusion

In mice, heparin seems like a suitable anticoagulant for obtaining plasma for multiplex assays for the cytokines IL-1α, IL-1β, IL-2, IL-6, IL-9, IL-12p40, IL-12p70, IL-13, G-CSF, GM-CSF, IFN-γ, KC, MCP-1, MIP-1α, MIP-1β, RANTES and TNFα, but an effect of heparin in high concentrations should be considered for the cytokines IL-9, IL-12p40, IL-12p70, KC, MCP-1, MIP-1β and RANTES. Short isoflurane anesthesia had significant impact on G-CSF, but none of the other cytokines.     

Acute phase response in porcine reproductive and respiratory syndrome virus infection

This study was focused on the changes observed in the serum concentration of haptoglobin (Hp), C-reactive protein (CRP), serum amyloid A (SAA) and Pig-major acute protein (Pig-MAP), during experimental porcine reproductive and respiratory syndrome virus (PRRSV) infection and in their relationship with the expression of interleukin 1β (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α). Hp and Pig-MAP serum levels were increased at 10 dpi, but CRP and SAA showed a delayed and highly variable increase. All three proinflammatory cytokines were poorly expressed, and only a mild increase in IL-1β was observed at 7 dpi. The increased expression of Hp coincided with the light enhancement observed in both IL-6 and TNF-α, and might be related with an increased expression of IL-10. The low expression of TNF-α might point to a possible mechanism of viral evasion of host-immune response. This issue and the delayed expression of CRP and SAA should be taken into account in future studies about modulation of the immune response by PRRSV infection.     

Ex vivo generation of mature equine monocyte-derived dendritic cells

Dendritic cells (DCs) are innate immune cells specialized in antigen detection and presentation. They perform an essential role in initiating and guiding the immune response, the direction of which largely depends upon the activation state of the DCs. The objective of this study was to generate mature equine monocyte-derived DCs and, in doing so, to develop a method for measuring the activation state of these cells. Equine DCs were stimulated with UV-inactivated Escherichia coli (E. coli), and the activation status was measured by analyzing cell surface marker expression, cytokine production, and endocytic capacity. Comparisons for each parameter measured were performed between macrophages, non-stimulated DCs and stimulated DCs. Equine monocyte-derived DCs may be distinguished from macrophages based on cell surface expression of MHC class II (p < 0.0001) and CD206 (p < 0.0001), their capacity for endocytosis of FITC-dextran (p < 0.05), and production of TNF-α upon stimulation (p < 0.001). Furthermore, stimulated DCs can be distinguished from non-stimulated DCs based on increased cell surface expression of MHC class II (p < 0.0001) and upregulation of pro-inflammatory cytokine mRNA, particularly IL-12/IL-23p40 (p < 0.05) and IL-23p19 (p < 0.05). The ability to measure DC activation state will facilitate future investigations of equine DC function.