Histological and immunohistochemical characterization of mucosa-associated lymphoid tissue and antigen-presenting cells in trachea and lung of cattle

The presence of bronchus-associated lymphoid tissue (BALT) and its structural components has been described in different healthy animal species and in animals with diseases of the respiratory tract. In contrast to normal mammals, BALT is absent in healthy human adult lungs, but has been found in the lungs of children. The histological characteristics of organized mucosa-associated lymphoid tissue (MALT), its subsets of immune cells and their in situ distribution in the lung of healthy subadult and adult cattle shows close similarities with BALT in humans and other animal species such as sheep, horses and pigs. This study clearly demonstrates that organized MALT also occurs in the tracheal mucosa of cattle. The absence of tracheal MALT and BALT in calves suggest that these structures are not constitutive. In the mucosa of bovine trachea, bronchi and bronchioli, MHC II+ and CD11c+ dendritic cells (DCs) are located in the epithelium and in the lamina propria mucosae. These DCs are already present in calves soon after birth. Examination of tangential epithelial sheets shows that in the bovine tracheal epithelium, like in man and rat, a dense network of MHC II+ and CD11c+ DCs exists and that their number is considerably higher than in conventional transverse sections. In the bovine tracheal and bronchial epithelium, MHC II+ DCs are extending their dendrites towards the lumen indicating that these DCs possibly are involved in sampling of luminal antigens. The presence of significantly higher numbers of MHC II+ DCs in the tracheal and bronchial/bronchiolar mucosa of older cattle in than in calves possibly results from local stimulation with exogenous antigens during postnatal life. Detection of DCs expressing the costimulatory molecules CD80 and CD86 in calves and cattle suggests maturation of DCs, which is most likely induced by stimulation with exogenous antigens.

Comparative analysis of antigen-presenting cells in gingival tissues in healthy and periodontitis patients

AIMS

Microbial flora of dental plaque trigger innate and adaptive immune responses. The function of antigen-presenting cells (APCs) is to bridge the innate and adaptive immune systems. The human immune system contains three main types of APCs: dendritic cells (DC) (Langerhans cells (LCs) and interstitial DCs, IDCs), macrophages and B lymphocytes. In this study, the distribution and density of all APCs in healthy and inflamed human gingival tissue were comparatively analysed.

METHODS

Research was conducted on gingival biopsy specimens obtained from 55 patients and classified in three groups: healthy gingiva (control group, n=10), moderate periodontal disease (PD) (n=21) and severe PD (n=24). For APCs' identification antibodies raised against CD_1a (for LCs), S₁₀₀ protein (for iDCs), CD₆₈ (for macrophages) and CD₂₀ (for B lymphocytes) were used.

RESULTS

Increased density of IDCs, macrophages and B lymphocytes in lamina propria and reduced density of LCs in the gingival epithelium were found in patients with periodontitis. Simultaneously, it was noticed an increased concentration of macrophages and B cells in the gingival epithelium in patients with PD. No statistically significant difference in the distribution and density of APC was found among patients with moderate and advanced periodontitis.

CONCLUSIONS

It was hypothesised that in the periodontitis the role of antigen presentation was largely taken from LCs by the DCs, macrophages and B cells. These APCs are thought to have less protective and tolerogenic potential than LCs and this is a significant reason for alveolar bone destruction in periodontitis.

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.

Melatonin administration provokes the activity of dendritic reticular cells in the seminal vesicle of Soay ram during the non-breeding season

Dendritic cells (DCs) are innate immune cells which engulf, process and present antigens to the naïve T-lymphocyte cells. However, little is known about the effect of melatonin on the DCs. The present study aimed to investigate the morphology and distribution of the DCs by transmission electron microscopy and Immunohistochemistry after melatonin administration. A total of 8 out of 15 adult ram was randomly selected to receive the melatonin implant and the remaining 7 animals received melatonin free implants. DCs showed positive immunoreactivity for CD117, S-100 protein and CD34. There is an obvious increase in the number of the positive immunoreactive cells to CD3, estrogen receptor alpha and progesterone in the treated groups. The expression of CD56 and MHCII in the DCs was abundant in the treated groups. The ultrastructure study revealed that melatonin exerts a stimulatory effect on the DCs which was associated with increment in the secretory activity of DCs. The secretory activity demarcated by an obvious increase in the number of mitochondria, cisternae of rER and a well-developed Golgi apparatus. The endosomal- lysosomal system was more developed in the treated groups. A rod-shaped Birbeck granule was demonstrated in the cytoplasm of the melatonin treated group. DCs were observed in a close contact to telocytes, T-Lymphocytes, nerve fibers and blood vessels. Taken together, melatonin administration elicits a stimulatory action on the DCs and macrophages through increasing the size, the number and the endosomal compartments which may correlate to increased immunity.

FOXP3, CD208, and CD206 Expression in Canine Cutaneous Histiocytoma

Canine cutaneous histiocytoma (CCH) is a noninfectious tumor that spontaneously regresses. It is suggested that this regression is due to tumor cell maturation, which is responsible for CD8 lymphocyte activation and tumor cell destruction. Nevertheless, the possible role of the immune microenvironment in tumor regression has not been investigated to date. The aim of this study was to investigate the expression of CD208 and FoxP3 as markers of dendritic cells and regulatory T lymphocytes, respectively, and tumor cell expression of CD206 as a marker of Langerhans cell activation, and relate these parameters to the different phases of CCH and to intratumoral T cell infiltration. Formalin-fixed, paraffin-embedded samples from 31 CCH were evaluated. In each case, the mitotic count and regression phase were recorded. Within the tumor, a quantitative evaluation of immunolabeled CD208⁺ cells, FoxP3⁺ cells, and CD3⁺ lymphocytes was performed, as well as the CD206⁺ tumor cell location. Intratumoral CD208⁺ cells correlated with CD3⁺ lymphocytic infiltration. The possible role of dendritic cells in tumor regression was not confirmed since CD208 seemed to be a nonspecific marker for canine dendritic cells. FoxP3⁺ lymphocyte density was not correlated with any parameter. Neoplastic Langerhans cells presented progressive CD206 expression, from the bottom of the tumor to the epidermis, which correlated with the tumor regression phase and with intratumoral T lymphocyte infiltration. In conclusion, we confirmed a CD206 phenotype change in tumor cells in a spatial group-related pattern, supporting the hypothesis that tumoral Langerhans cells acquire a mature phenotype with tumor regression.

Histological and Immunohistochemical Features of Normal Histiocytes and Langerhans Cells, and Histiocytic Sarcomas in Four-Toed Hedgehogs (Atelerix albiventris)

Histiocytic sarcoma (HS) is a haematopoietic tumour of histiocyte origin that has been sporadically reported in four-toed hedgehogs (Atelerix albiventris). The present study aimed to investigate clinical, gross, histopathological and immunohistochemical features of HS in eight hedgehogs. Histological and immunohistochemical features of normal histiocytes and Langerhans cells (LCs) of hedgehogs were also investigated. HLA-DR-, Iba-1- and E-cadherin-positive LCs were observed in the epidermis, while Iba-1- and CD204-positive histiocytes were detected in the lymph nodes and spleen of normal hedgehogs. Localized HS (six cases) developed in the skin and spleen, while disseminated HS (two cases) occurred in the intestine. Tumour cells of disseminated HS were also distributed within the mesenteric lymph nodes, liver, kidney, spleen, lung and adrenal glands. Tumour cells of both localized and disseminated HS were composed of histiocytic cells, spindle to pleomorphic cells, multinucleated giant cells and erythrophagocytic cells. Most tumour cells were immunopositive for Iba-1, CD204 and lysozyme. A small number of tumour cells were positive for E-cadherin and CD208, and the tumour cells in one case were positive for HLA-DR. These results suggest that the tumour cells have variable features of histiocyte origin, including dendritic cells, LCs and macrophages. The behaviour of HS in the hedgehog was very aggressive, and 50% of cases died within 90 days of resection. The present study also highlighted the tendency for local tumour recurrence in localized cutaneous HS cases, suggesting a requirement for a long-term follow-up after excision.

Theileria annulata transformation altered cell surface molecules expression and endocytic function of monocyte-derived dendritic cells

Theileria annulata is a protozoan parasite transmitted by ticks to cattle. The most important processes of T. annulata are the infection and transformation of host monocytes, which promote cell division and generate a neoplastic phenotype. Dendritic cells play an important role in the development of adaptive immune responses against parasites and are traditionally classified into four types. One type of dendritic cell derived from afferent lymph was successfully transformed by T. annulata in vitro in a previous report. However, whether the monocyte-derived dendritic cells could be transformed and how the endocytic function is affected by T. annulata infection were not yet known. Bovine dendritic cells (DCs) derived from blood CD14⁺ monocytes were cocultured with T. annulata sporozoites in vitro. On day 15 post infection, rounded and continuously proliferating cells were observed. The effect of this transformation on cell phenotype was studied using immunostaining and flow cytometry. After transformation, the cells maintained the expression of the DC-specific marker CD11c, but it was downregulated as were the expression of CD11b, CD14 and CD86. In contrast, CD205, CD45 and MHC class Ⅱ molecules were upregulated in transformed cells. The levels of CD172a, CD21, CD40 and CD80 expression were very low in the transformed cells (<1 %). However, the transformed cells maintained high expression levels of MHC Ⅰ (>99 %). In addition, the normal and transformed DCs were cocultured with OVA-FITC antigen to compare the differences of the endocytic functions between these two types of cells. The results revealed that the endocytic functions of MoDCs were significantly inhibited after transformation by T. annulata.

Immunophenotyping of Sheep Paraffin-Embedded Peripheral Lymph Nodes

Sheep are not only a major livestock species globally, they are also an important large animal model for biomedical research and have contributed to our understanding of the ontogeny and architecture of the mammalian immune system. In this study, we applied immunohistochemistry and multicolor immunofluorescence in fixed and paraffin-embedded lymph nodes to phenotype the key populations of antigen presenting cells, lymphocytes, and stromal cells that orchestrate the host adaptive immune response. We used an extensive panel of antibodies directed against markers associated with dendritic cells (MHC class II, CD83, and CD208), macrophages (CD11b, CD163, and CD169), stromal cells (CNA.42, S100, and CD83), and lymphocytes (CD3, Pax5, CD4, CD8). Using different methods of tissue fixation and antigen retrieval, we provide a detailed immunophenotyping of sheep lymph nodes including the identification of potential subpopulations of antigen presenting cells and stromal cells. By characterizing cells expressing combinations of these markers in the context of their morphology and location within the lymph node architecture, we provide valuable new tools to investigate the structure, activation, and regulation of the sheep immune system in health and disease.

Evaluation of a panel of antibodies for the immunohistochemical identification of immune cells in paraffin-embedded lymphoid tissues of new- and old-world camelids

Different species of camelids play an important role in the epidemiology of various emerging infectious diseases such as Middle East respiratory syndrome. For precise investigations of the immunopathogenesis in these host species, appropriate immunohistochemical markers are highly needed in order to phenotype distinct immune cells populations in camelids. So far, specific immunohistochemical markers for camelid immune cells are rarely commercially available, and cross-reactivity studies are restricted to the use of frozen dromedary tissues. To bridge this gap, 14 commercially available primary antibodies were tested for their suitability to demonstrate immune cell populations on formalin fixed paraffin-embedded (FFPE) tissue sections of dromedaries, Bactrian camels, llamas, and alpacas in the present study. Out of these, 9 antibodies directed against CD3, CD20, CD79α, HLA-DR, Iba-1, myeloid/histiocyte antigen, CD204, CD208, and CD68 antigen exhibited distinct immunoreaction patterns to certain camelid immune cell subsets. The distribution of these antigens was comparatively evaluated in different anatomical compartments of thymus, spleen, mesenteric, and tracheobronchial lymph nodes. The presented results will provide a basis for further investigations in camelids, especially with respect to the role of the immune response in certain infectious diseases, which harbor a considerable risk to spill over to other species.

Bovine Viral Diarrhea Virus Infects Monocyte-Derived Bovine Dendritic Cells by an E2-Glycoprotein-Mediated Mechanism and Transiently Impairs Antigen Presentation

Infection of professional antigen presenting cells by viruses can have a marked effect on these cells and important consequences for the generation of subsequent immune responses. In this study, we demonstrate that different strains of bovine viral diarrhea virus (BVDV) infect bovine dendritic cells differentiated from nonadherent peripheral monocytes (moDCs). BVDV did not cause apoptosis in these cells. Infection of moDC was prevented by incubating the virus with anti-E2 antibodies or by pretreating the cells with recombinant E2 protein before BVDV contact, suggesting that BVDV infects moDC through an E2-mediated mechanism. Virus entry was not reduced by incubating moDC with Mannan or ethylenediaminetetraacetic acid (EDTA) before infection, suggesting that Ca(2+) and mannose receptor-dependent pathways are not mediating BVDV entry to moDC. Infected moDC did not completely upregulate maturation surface markers. Infection, but not treatment with inactivated virus, prevented moDC to present a third-party antigen to primed CD4(+) T cells within the first 24 hours postinfection (hpi). Antigen-presenting capacity was recovered when viral replication diminished at 48 hpi, suggesting that active infection may interfere with moDC maturation. Altogether, our results suggest an important role of infected DCs in BVDV-induced immunopathogenesis.

Immunopathologic Changes in the Thymus of Calves Pre-infected with BVDV and Challenged with BHV-1

The aim of this work was to investigate the effect of pre-infection with bovine viral diarrhoea virus (BVDV) on thymus immune cells from calves challenged with bovine herpesvirus 1 (BHV-1). Twelve Friesian calves, aged 8 to 9 months, were inoculated with non-cytopathic BVDV-1. Ten of them were subsequently challenged with BHV-1 and euthanized in batches of two at 1, 2, 4, 7 or 14 dpi with BHV-1. The other two calves were euthanized prior to the second inoculation and were used as BVDV-infected controls. A further 10 calves were inoculated solely with BHV-1 and euthanized at the same time points. Two calves were not inoculated with any agent and were used as negative controls. Quantitative changes in immune cells were evaluated with immunohistochemical methods to compare coinfected calves and calves challenged only with BHV-1. The results of this study pointed out BVDV as responsible for the thymic lesions observed in the experiment as well as for the majority of immunopathologic changes, including a downregulation of Foxp3 lymphocytes and TGFβ, which reverted as BVDV was cleared, and an overexpression of medullary CD8+ T cells. However, despite not inducing evident lesions in the thymus, BHV-1 seemed to prompt some immune alterations. Collectively, these data contribute to the knowledge on the immunopathologic alterations of the thymus during BVDV infections, and its importance in the development of secondary infections.

Characterization of thymus atrophy in calves with subclinical BVD challenged with BHV-1

Since the thymus is a target organ for the bovine viral diarrhea virus (BVDV), our experiment aimed to understand its relationship with the immunosuppressive effect by studying the consequences of a previous infection with BVDV on the thymus of calves challenged with bovine herpesvirus 1.1 (BHV-1). For this purpose, 12 animals were inoculated intranasally with non-cytopathic BVDV-1; 12 days later, 10 of them were coinfected intranasally with BHV-1. These animals were euthanized in batches of two at 0, 1, 2, 4, 7 or 14 dpi with BHV-1. Another 10 calves were inoculated solely with BHV-1 and euthanized in batches of two at 1, 2, 4, 7 or 14 dpi with BHV-1; two uninoculated calves were used as negative controls. Thymus samples from these animals were processed for viral detection and histopathological, immunohistochemical, and ultrastructural studies focused on BVDV/BHV-1 antigens, cortex:medulla ratio, apoptosis (TUNEL and caspase-3), collagen deposition, and factor VIII endothelial detection. Our study revealed the immunohistochemical presence of BVDV antigen in all animals in the BVDV-infected group, unlike BHV-1 detection, which was observed in animals in both infection groups only by molecular techniques. BVDV-preinfected animals showed severe atrophic changes associated with reduced cortex:medulla ratio, higher presence of cortical apoptosis, and increased collagen deposition and vascularization. However, calves solely infected with BHV-1 did not show atrophic changes. These findings could affect not only the numbers of circulating and local mature T cells but also the T cell-mediated immunity, which seems to be impaired during infections with this virus, thus favoring pathogenic effects during secondary infections.

Severe thymic hyperplasia in a newborn calf associated with impaired T-cell differentiation

A 1-day-old female Holstein–Friesian calf was presented for severe dyspnea. Physical examination revealed respiratory distress, moderate edema of the ventral neck, and swollen jugular veins. The calf died and was submitted for necropsy. A severely enlarged thymus (40 cm × 20 cm × 10 cm) weighing 1.37 kg was detected on gross examination. Histomorphology was normal but no tingible body macrophages were observed in the medullary areas. Immunohistochemistry was characterized by the lack of thymic cluster of differentiation 3 and major histocompatibility complex class II expression compared to age-matched controls. The findings were consistent with severe thymic hyperplasia, a rare congenital condition that is also described in children. Immunohistochemical findings were suggestive of impaired T-cell development and selection associated with lack of apoptosis of thymic cells (lack of tingible body macrophages). Thymic hyperplasia in juvenile animals should be considered among the differential diagnoses of mediastinal masses as a rare cause of respiratory distress in newborn calves.