Immunophenotyping of Sheep Paraffin-Embedded Peripheral Lymph Nodes

A comprehensive study of CYP2E1 and its role in carcass characteristics and chemical lamb meat quality in different Indonesian sheep breeds

The role of CYP2E1 in oxidation is essential for its effects on meat quality. This study used 200 Indonesian sheep (Ovis aries) to determine the SNP g allele frequencies. g. 50658168 T>C of CYP2E1 gene located in 3´-UTR region and their genetic association with lamb quality traits, including carcass characteristics, retail cut carcass, physicochemical lamb, fatty acid, cholesterol, flavor and odor, and mineral content. Further, the level of CYP2E1 mRNA and CYP2E1 protein expression in muscle were determined and correlated with lamb quality traits. CYP2E1 gene polymorphisms were identified using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) analysis. The CYP2E1 mRNA expression levels in phenotypically divergent sheep populations were analyzed using Quantitative Real Time-PCR (qRT-PCR). Immunohistochemistry (IHC) and hematoxylin-eosin (HE) staining analysis used three samples each in the high and low lamb quality groups based on pH value and tenderness. An association study of CYP2E1 gene polymorphisms was performed using General Linear Model (GLM) analysis. The genetic association between the CC, CT, and TT genotypes at the SNP g. 50658168 T>C CYP2E1 gene and lamb quality traits were significant (P<0.05), including carcass characteristics, retail cut carcass, fatty acid, cholesterol, flavor, and odor. Lambs with the CT genotype had a higher mRNA and protein expression in high lamb quality traits. The highest CYP2E1 protein expression was localized in the longissimus dorsi. The group sample with high lamb quality had a higher area and perimeter of muscle cells. CYP2E1 can be used as a genetic marker for selecting sheep with high meat quality.

ORF virus causes tumor-promoting inflammation in sheep and goats

ORF virus (ORFV) causes contagious ecthyma ("ORF"), a disease of sheep and goats characterized by lesions ranging from vesicles and pustules to atypical papilloma-like and angiomatous lesions in the skin and mucosae. The authors investigated the molecular factors leading to the ORF-associated atypical tumor-like changes. Fifteen lambs, 15 kids, and an adult ram clinically affected by natural ORFV infection were enrolled in the study and examined by several methods. ORFV was detected by viral culture or real-time polymerase chain reaction (RT-PCR) in the lesioned tissues and in the blood of the clinically affected sheep and goats. Surprisingly, ORFV was also detected in the blood of healthy goats from an affected herd. Microscopically, they found a pseudo-papillomatous proliferation of the epithelium, while the dermis and lamina propria were expanded by a proliferating neovascular component that highly expressed the viral vascular endothelial growth factor (vVEGF) and its host receptor vascular endothelial growth factor receptor 2 (VEGFR2). Immunohistochemistry, immunofluorescence, and in situ hybridization for mRNA showed that epidermal growth factor receptor (EGFR) was expressed in the fibrovascular component, in the infiltrating CD163+ macrophages, and in the basal stratum of the epidermis. Confocal immunofluorescence microscopy demonstrated that CD163+ macrophages were associated with VEGF and VEGFR2. Finally, they found by quantitative RT-PCR the overexpression of the interleukin-6 and VEGFR2 genes in the lesioned tissues. These findings suggest that ORFV activates an inflammatory reaction characterized by CD163+ macrophages expressing EGFR and VEGFR2, which might play an oncogenic role through synergistic action with vVEGF signaling.

Comparative proteomic profiling of the ovine and human PBMC inflammatory response

Understanding the cellular and molecular mechanisms of inflammation requires robust animal models. Sheep are commonly used in immune-related studies, yet the validity of sheep as animal models for immune and inflammatory diseases remains to be established. This cross-species comparative study analyzed the in vitro inflammatory response of ovine (oPBMCs) and human PBMCs (hPBMCs) using mass spectrometry, profiling the proteome of the secretome and whole cell lysate. Of the entire cell lysate proteome (oPBMCs: 4217, hPBMCs: 4574 proteins) 47.8% and in the secretome proteome (oPBMCs: 1913, hPBMCs: 1375 proteins) 32.8% were orthologous between species, among them 32 orthologous CD antigens, indicating the presence of six immune cell subsets. Following inflammatory stimulation, 71 proteins in oPBMCs and 176 in hPBMCs showed differential abundance, with only 7 overlapping. Network and Gene Ontology analyses identified 16 shared inflammatory-related terms and 17 canonical pathways with similar activation/inhibition patterns in both species, demonstrating significant conservation in specific immune and inflammatory responses. However, ovine PMBCs also contained a unique WC1+γδ T-cell subset, not detected in hPBMCs. Furthermore, differences in the activation/inhibition trends of seven canonical pathways and the sets of DAPs between sheep and humans, emphasize the need to consider interspecies differences in translational studies and inflammation research.

Liver Histopathological and Immunohistochemical Evaluation from Fasciola hepatica Experimentally Infected and Reinfected Sheep

Fasciolosis is an important economic disease of livestock. There is a global interest in the development of protective vaccines since the current anthelmintic therapy is no longer sustainable. A better knowledge of the host-parasite interaction is needed to design effective vaccines. To date, few studies have evaluated host-parasite interaction by comparing infected and reinfected animals. The present study evaluates the microscopical hepatic lesions in sheep infected and reinfected with Fasciola hepatica during the acute and chronic stages of infection. The histopathological study revealed the presence of necrotizing foci (NF1) associated with larvae migration during the early stages of infection in the primoinfected (PI) and reinfected (RI) groups. In the late stages of infection of the PI group and at the early and late stages of infection in the RI groups, extensive necrotizing/hemorrhagic foci (NF2) were found in the vicinity of enlarged bile ducts, some containing adult flukes, suggesting parasites may have caused NF2 while feeding. The immunohistochemical study revealed an increase in Foxp3+ T cells in both PI and RI groups with respect to the UC group and in the infiltrates adjacent to NF1 in the RI groups with respect to the PI group, suggesting the F. hepatica induce Foxp3 T cell expansion to facilitate parasite survival. In addition, in both the PI and RI groups, and during acute and chronic stages of the infection, a poor expression of iNOS was found accompanied by a strong expression of CD163, suggesting a marked M2 activation of macrophages in the hepatic lesions, which may be related with healing processes, and it also may facilitate parasite survival. The main differences between PI and RI animals were the more severe infiltration of eosinophils and Foxp3+ T cells, whereas RI did not modify M2 activation of macrophages which occurs since the early stages of primoinfection.

Characteristics of nasal mucosal barrier in lambs at different developmental stages

The mucosal barriers of a lamb's nasal cavity are composed of a multi-layer barrier designed to protect against the invasion of harmful microorganisms. However, despite the protective measures, respiratory pathogens still infect the sheep from the nasal cavity. Therefore, our study aimed to investigate the characteristics of lamb's nasal cavity barrier at different developmental stages. For nasal histological characteristics, our study revealed that the conchoidal curvature of the inferior nasal conch and the number of glands significantly increased with lamb development. For nasal mucosal barrier characteristics, physical and immune barriers were carefully explored. Initially, we observed that the thickness and proliferative capacity of nasal epithelial significantly increased from fetal to 21 days, which then decreased at 60 days. Then, our study showed that the number of goblet cells (GCs) of 21 days old lamb was significantly higher than in other stages of development. Besides, we found that the number of nasal immune cells, such as dendritic cells, CD3⁺ T cells, IgA⁺ B cells, and nasal-associated lymphoid tissue (NALT), were all significantly increased not only from the proximal to distal side in the nasal cavity but also with their age. Totally, our study revealed various characteristics of the mucosal barriers of a lamb's nasal cavity, which provide a reference for explaining the susceptibility of respiratory tract infection in lambs.

Theileriosis in naturally infected roan antelope (Hippotragus equinus)

Cases of Theileria-associated mortality are rarely reported in African wild artiodactyls. Descriptions of lesions are limited, particularly in endangered hippotraginids. Here, we analyzed retrospectively the gross and histologic findings in 55 roan antelope (Hippotragus equinus) with fatal natural theileriosis. The most frequently recorded gross findings in 40 cases were widespread petechiae and ecchymoses (72.5%), probable anemia (67.5%), icterus (60%), splenomegaly (60%), hepatomegaly (52.5%), and pulmonary edema (50%). Histologic lesions in 34 cases were characterized by multi-organ infiltrates of parasitized and nonparasitized mononuclear leukocytes (MLs), and fewer multinucleate giant cells (MNGCs). Liver, lung, kidney, adrenal gland, and heart were most consistently infiltrated, followed by spleen and lymph nodes. Leukocytes were phenotyped in lung, liver, kidney, and heart specimens from 16 cases, using immunohistochemistry to detect CD20, CD3, myeloid/histiocyte antigen (MAC387), IBA-1, and CD204 surface receptors. A roan polyclonal anti-Theileria sp. (sable) antibody was applied to the same tissues to identify intraleukocytic parasite antigens. Similar proportions of intravascular and extravascular IBA-1-, CD204-, and MAC387-reactive putative monocyte-macrophages and fewer CD3-positive putative T-lymphocytes were identified in all organs, especially the lungs in infected roan. CD20-positive putative B-lymphocytes were significantly scarcer than in uninfected controls. Intraleukocytic Theileria parasites labeled consistently in affected tissues. Some parasitized and nonparasitized MLs and the MNGCs failed to label with selected leukocyte markers. Fatal theileriosis in roans may largely be the result of multi-organ monocyte-macrophage activation with associated tissue injury and overwhelming systemic inflammation. The identity of the parasitized leukocytes and characteristics of the lymphohistiocytic response require further clarification in roans.

Pathological and protective roles of dendritic cells in Mycobacterium tuberculosis infection: Interaction between host immune responses and pathogen evasion

Dendritic cells (DCs) are principal defense components that play multifactorial roles in translating innate immune responses to adaptive immunity in Mycobacterium tuberculosis (Mtb) infections. The heterogeneous nature of DC subsets follows their altered functions by interacting with other immune cells, Mtb, and its products, enhancing host defense mechanisms or facilitating pathogen evasion. Thus, a better understanding of the immune responses initiated, promoted, and amplified or inhibited by DCs in Mtb infection is an essential step in developing anti-tuberculosis (TB) control measures, such as host-directed adjunctive therapy and anti-TB vaccines. This review summarizes the recent advances in salient DC subsets, including their phenotypic classification, cytokine profiles, functional alterations according to disease stages and environments, and consequent TB outcomes. A comprehensive overview of the role of DCs from various perspectives enables a deeper understanding of TB pathogenesis and could be useful in developing DC-based vaccines and immunotherapies.

Baseline T-lymphocyte and cytokine indices in sheep peripheral blood

Background

Sheep are an important livestock species worldwide and an essential large-animal model for animal husbandry and veterinary research. Understanding fundamental immune indicators, especially T-lymphocyte parameters, is necessary for research on sheep diseases and vaccines, to better understand the immune response to bacteria and viruses for reducing the use of antibiotics and improving the welfare of sheep. We randomly selected 36 sheep of similar ages to analyze cell-related immune indicators in peripheral blood mononuclear cells (PBMCs). The proportions of CD4⁺ and CD8⁺ T cells in PBMCs were detected by flow cytometry. We used Concanavalin A (Con A) and Phorbol-12-myristate-13-acetate (PMA)/Ionomycin to stimulate PBMCs, and measured the expression of IFN-γ, IL-4, and IL-17A using enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunospot assay (ELISpot). Simultaneously, PMA/Ionomycin/brefeldin A (BFA) was added to PBMCs, then the expression of IFN-γ, IL-4, and IL-17A was detected by flow cytometry after 4 h of culturing. In addition, we observed the proliferation of PBMCs stimulated with Con A for 3, 4, and 5 days.

Results

The proportions of CD4⁺ T lymphocytes (18.70 ± 4.21%) and CD8⁺ T lymphocytes (8.70 ± 3.65%) were generally consistent among individuals, with a CD4/CD8 ratio of 2.40 ± 0.79. PBMCs produced high levels of IFN-γ, IL-4, and IL-17A after stimulation with PMA/Ionomycin and Con A. Furthermore, PMA/Ionomycin stimulation of PBMC yielded significantly higher cytokine levels than Con A stimulation. Flow cytometry showed that the level of IFN-γ (51.49 ± 11.54%) in CD8⁺ T lymphocytes was significantly (p < 0.001) higher than that in CD4⁺ T lymphocytes (14.29 ± 3.26%); IL-4 (16.13 ± 6.81%) in CD4⁺ T lymphocytes was significantly (p < 0.001) higher than that in CD8⁺ T lymphocytes (1.84 ± 1.33%), There was no difference in IL-17A between CD4⁺ (2.83 ± 0.98%) and CD8⁺ T lymphocytes (1.34 ± 0.67%). The proliferation of total lymphocytes, CD4⁺ T lymphocytes, and CD8⁺ T lymphocytes continued to increase between days 3 and 5; however, there were no significant differences in proliferation between the cell types during the stimulation period.

Conclusions

Evaluating primary sheep immune indicators, especially T lymphocytes, is significant for studying cellular immunity. This study provided valuable data and theoretical support for assessing the immune response of sheep to pathogens and improving sheep welfare.

Repopulation of decellularised porcine pulmonary valves in the right ventricular outflow tract of sheep: Role of macrophages

The primary objective was to evaluate performance of low concentration SDS decellularised porcine pulmonary roots in the right ventricular outflow tract of juvenile sheep. Secondary objectives were to explore the cellular population of the roots over time. Animals were monitored by echocardiography and roots explanted at 1, 3, 6 (n = 4) and 12 months (n = 8) for gross analysis. Explanted roots were subject to histological, immunohistochemical and quantitative calcium analysis (n = 4 at 1, 3 and 12 months) and determination of material properties (n = 4; 12 months). Cryopreserved ovine pulmonary root allografts (n = 4) implanted for 12 months, and non-implanted cellular ovine roots were analysed for comparative purposes. Decellularised porcine pulmonary roots functioned well and were in very good condition with soft, thin and pliable leaflets. Morphometric analysis showed cellular population by 1 month. However, by 12 months the total number of cells was less than 50% of the total cells in non-implanted native ovine roots. Repopulation of the decellularised porcine tissues with stromal (α-SMA+; vimentin+) and progenitor cells (CD34+; CD271+) appeared to be orchestrated by macrophages (MAC 387+/ CD163low and CD163+/MAC 387-). The calcium content of the decellularised porcine pulmonary root tissues increased over the 12-month period but remained low (except suture points) at 401 ppm (wet weight) or below. The material properties of the decellularised porcine pulmonary root wall were unchanged compared to pre-implantation. There were some changes in the leaflets but importantly, the porcine tissues did not become stiffer. The decellularised porcine pulmonary roots showed good functional performance in vivo and were repopulated with ovine cells of the appropriate phenotype in a process orchestrated by M2 macrophages, highlighting the importance of these cells in the constructive tissue remodelling of cardiac root tissues.

Integration and functional performance of a decellularised porcine superflexor tendon graft in an ovine model of anterior cruciate ligament reconstruction

The objective was to evaluate the performance of decellularised porcine superflexor tendon (pSFT) as an anterior cruciate ligament (ACL) reconstruction device. The ACL of adult sheep was reconstructed with decellularised pSFT or ovine allograft SFT and animals sacrificed at 4, 12 and 26 weeks (n = 4 per group) for biological evaluation and 26 weeks (n = 6) for biomechanical evaluation of the grafts. Both grafts showed good in vivo performance with no major differences at macroscopic evaluation post euthanasia. Histopathology revealed an inflammatory reaction to both grafts at 4 weeks, which reduced by 26 weeks. There was advanced cellular ingrowth from 12 weeks, ligamentisation of intra-articular grafts, ossification and formation of Sharpey's fibers at the graft/bone junctions. Immunohistochemistry showed that at 4 and 12 weeks, the host response was dominated by CD163+ M2 macrophages and a cell infiltrate comprising α-SMA + myofibroblasts, CD34+ and CD271+ progenitor cells. At 26 weeks the biomechanical properties of decellularised pSFT and oSFT grafts were comparable, with all grafts failing in the intra-articular region. This study provides new insight into constructive remodelling of tendons used for ACL replacement and evidence of integration and functional performance of a decellularised xenogeneic tendon with potential as an alternative for ACL reconstruction.

Virus distribution and early pathogenesis of highly pathogenic peste-des-petits-ruminants virus in experimentally infected goats

INTRODUCTION

Despite causing one of the most dreaded diseases of small ruminants, relatively little is known about the pathogenic events, antigen distribution and the cells responsible for the uptake and transmission of peste-des-petits-ruminants virus (PPRV) during primitive stages of infection.

OBJECTIVES

We aimed at deciphering the sequential tissue tropism, pathological events and putative role of M2c macrophages during incubatory, prodromal and invasive stages of PPRV infection.

METHODOLOGY

A total of 10 goats were sequentially sacrificed at 1, 2, 3, 4, and 5 days post-infection (dpi, n = 2 per time-point) following intranasal inoculation with a highly virulent strain of PPRV (lineage IV PPRV/Izatnagar/94). Histological evaluation to assess PPRV mediated pathologies, RT-qPCR and immunohistochemistry (IHC) to decipher sequential virus distribution, and dual immunolabelling to determine the role of M2c macrophage in early PPRV uptake and transmission was performed.

RESULTS

PPRV/Izatnagar/94 caused major pathologies in the lung tissues. Unprecedentedly, PPRV nucleic acid and antigens were detected in various tissues as early as one dpi. RT-qPCR revealed PPRV in the nasal cavity, trachea, bronchi, tongue and lymph nodes draining these tissues from 1 dpi. IHC affirms cells residing in the lamina propria and submucosa of the respiratory tract and tongue and peribronchiolar areas of lungs as the primary target of PPRV. Following initial replication in the respiratory tract, PPRV is transmitted to the regional lymph nodes where primary viral amplification occurs. After viraemia and secondary replication in generalized lymphoid tissues, PPRV infects and replicates in the epithelial cells. Further, we localized CD163⁺ M2c macrophages in the goat tissues, but dual IHC elucidated that M2c macrophages do not facilitate uptake and transmission of PPRV during the early stages of infection.

CONCLUSION

Our study substantiates the disease establishment process and pathogenesis of PPRV/Izatnagar/94 during the incubatory and prodromal stages of infection. Further, we have also observed M2c macrophage distribution in the goat tissues and demonstrated that they do not pick and transmit PPRV.

A Partially Protective Vaccine for Fasciola hepatica Induced Degeneration of Adult Flukes Associated to a Severe Granulomatous Reaction in Sheep

Simple Summary

Fasciolosis is a parasitic disease of livestock causing important economic losses worldwide and it is also a zoonosis. Current therapy relies on the use of anthelmintic drugs, which is no longer sustainable due to the increase of anthelmintic resistance and the risk of drug residues in food. A deep understanding of the host-parasite interaction is required to develop protective vaccines for the control of fasciolosis. The aim of the present study is to evaluate the hepatic lesions in sheep vaccinated with a partly protective vaccine for F. hepatica, a non-protective vaccine and an infected control group. The protective vaccine showed less severe hepatic lesions than the infected control group. In addition, in the protective vaccine group dead flukes surrounded by a severe granulomatous inflammation were observed, which taken together with the lower fluke burden, suggests that the host response induced by the partially protective vaccine may have been involved in the death of adult flukes of F. hepatica. This is the first study reporting the presence of degenerated flukes associated to a severe granulomatous inflammation in bile ducts in a vaccine trial, a finding that would be useful for improving vaccine efficacy in future trials.

Abstract

Fasciolosis is an important economic disease of livestock. There is a global interest in the development of protective vaccines since current anthelmintic therapy is no longer sustainable. A better knowledge of the host-parasite interaction is needed for the design of effective vaccines. The present study evaluates the microscopical hepatic lesions in sheep immunized with a partially protective vaccine (VAC1), a non-protective vaccine (VAC2), and an infected control group (IC). The nature of granulomatous inflammation associated with degeneration of adult flukes found in the VAC1 group was characterized by immunohistochemistry. Hepatic lesions (fibrous perihepatitis, chronic tracts, bile duct hyperplasia, infiltration of eosinophils and lymphocytes and plasma cells) were significantly less severe in the VAC1 group than in the IC group. Dead adult flukes within bile ducts were observed only in the VAC1 group and were surrounded by a severe granulomatous inflammation composed by macrophages and multinucleate giant cells with a high expression of lysozyme, CD163 and S100 markers, and a low expression of CD68. Numerous CD3+ T lymphocytes and scarce infiltrate of FoxP3+ Treg and CD208+ dendritic cells were present. This is the first report describing degenerated flukes associated to a severe granulomatous inflammation in bile ducts in a F. hepatica vaccine trial.

Exogenous Small Ruminant Betaretrovirus Envelope Protein Is Detected in Draining Lymph Nodes in Contagious Respiratory Tumors of Sheep and Goats

Contagious respiratory tumors of sheep and goats are epithelial neoplasms of the lung and nasal cavities. They are associated with oncogenic betaretroviruses known as jaagsiekte sheep retrovirus and enzootic nasal tumor retrovirus of sheep and goats. We investigated the presence of the envelope protein (ENV) of these retroviruses in retropharyngeal and mediastinal lymph nodes using a specific monoclonal antibody by immunohistochemistry methods, single-labeled or combined with ovine B or T lymphocytes or macrophage cell markers. Samples of lymph nodes, fixed in formalin and zinc fixative, were obtained from paraffin-embedded material. Four groups of samples were used: 24 natural cases of ovine pulmonary adenocarcinoma (OPA), 13 of enzootic nasal adenocarcinoma of sheep (ENAS), 19 of enzootic nasal adenocarcinoma of goats (ENAG), and 14 control samples. ENV was detected by single labeling in cortical lymphoid follicles. Six of 24 OPA samples were positive and only in those from sheep with extensive neoplasia. Immunolabeling was detected in 5/13 ENAS and 10/19 ENAG samples. Positive labeling was found either in the intercellular spaces, membranes, or cytoplasm of cells in follicles. Control samples were not correspondingly labeled. Double immunohistochemistry demonstrated co-labeling of ENV and CD21 (B cells and follicular dendritic cells) in all samples, CD14 (macrophage) in OPA samples, and Pax-5 (B cells) in ENAG samples, but not with CD8 or CD4 (T lymphocytes). These results demonstrate the presence of betaretrovirus ENV proteins in nontumor cells in regional lymph nodes in sheep and goats with contagious respiratory tumors.

Diagnostic accuracy of ultrasound superb microvascular imaging for lymph nodes: A protocol for systematic review and meta-analysis

BACKGROUND

As a novel ultrasound technique, superb microvascular imaging can quickly, simply and noninvasively study the microvascular distribution in the tumor and evaluate the microvascular perfusion. Studies suggested that superb microvascular imaging is helpful for the differentiation between benign and malignant lymph nodes. However, the results of these studies have been contradictory. Therefore, the present meta-analysis aimed at determining the accuracy of superb microvascular imaging in the differential diagnosis between benign and malignant lymph nodes.

METHODS

We will search PubMed, Web of Science, Cochrane Library, and Chinese biomedical databases from their inceptions to the July 30, 2020, without language restrictions. Two authors will independently carry out searching literature records, scanning titles and abstracts, full texts, collecting data, and assessing risk of bias. Review Manager 5.2 and Stata14.0 software will be used for data analysis.

RESULTS

This systematic review will determine the accuracy of superb microvascular imaging in the differential diagnosis between benign and malignant lymph nodes.

CONCLUSION

Its findings will provide helpful evidence for the accuracy of superb microvascular imaging in the differential diagnosis between benign and malignant lymph nodes.

SYSTEMATIC REVIEW REGISTRATION

INPLASY202070133.

Characterization of dendritic cells and follicular dendritic cells in the hepatic lymph nodes and liver of sheep experimentally infected with Fasciola hepatica

Fasciola hepatica has been shown to have a high capacity for immunomodulation of the host response, making the development of protective vaccines extremely difficult. One of these immunomodulation mechanisms is the impairment of dendritic cells (DC) maturation and, therefore, suppression of antigenic presentation. The aim of this study was to evaluate the pathological changes as well as the characterization of two antigen presenting cells, DC (CD1b, CD83 and MHC-II positive) and follicular dendritic cells (FDC) (CNA.42, S100 and CD83 positive) by immunohistochemistry in the hepatic lymph nodes (HLN) and livers of sheep during the early stages of infection with F. hepatica [9 and 18 days post-infection (dpi)], compared with an uninfected group (UC) as a control. The results revealed a marked hyperplasia of HLN germinal centres at 9 and, in particular, 18 dpi, with respect to the UC group, with coincidental increased expression of CNA.42 in FDC of lymphoid follicles and CD1b in the DC of paracortical areas at 18 dpi. However, the expression of MHC-II and CD83 decreased at 9 and, particularly, at 18 dpi in HLN compared with that in the UC group. Since both markers are related to active presentation of antigens by DC and FDC, the results of the present study suggest that, despite the marked hyperplasia of HLN and increase in DC and FDC numbers during early stages of infection, the DC and FDC antigenic presentation capacity, as suggested by the expression of the markers MHC-II and CD83, is suppressed by the parasite. This suppression was not observed in the liver, probably because of the low number of DC. This is the first study of the immunophenotype of DCs and FDC in sheep infected with F. hepatica.