Macrophages are a type of white blood cell found in horses that play a significant role in the immune system. They are involved in the detection, phagocytosis, and destruction of bacteria and other harmful organisms. Additionally, macrophages contribute to tissue homeostasis and repair by removing dead cells and stimulating tissue regeneration. In horses, macrophages are distributed throughout various tissues, including the liver, lungs, and lymph nodes, where they help orchestrate the body's response to infection and injury. This page compiles peer-reviewed research studies and scholarly articles that explore the function, regulation, and clinical implications of macrophages in equine health.
Nixon AJ, Stashak TS, Smith FW, Norrdin RW.Carbon fibre-polylactic acid composites and monofilament non-absorbable suture material were compared for the repair of surgically transected superficial digital flexor tendons in 10 horses. All surgical wounds healed by first intention. The repaired tendons were enlarged, the carbon implanted tendons being larger than those sutured. The horses were killed at six, eight, 12,20 or 24 weeks. Greater fibrous thickening occurred in tendons repaired with carbon fibre, especially at 12 weeks postoperatively. Carbon fibre incited a greater histological response with macrophages, lymphocytes, plasma c...
Bailey M, Lloyd S, Martin SC, Soulsby EJ.Proliferation in vitro of peripheral blood lymphocytes both from horses infected with Strongylus vulgaris and from helminth-free ponies was observed in the presence of extracts of the fourth and fifth stage larvae and adults of S. vulgaris. In addition, S. vulgaris extracts induced transformation in cultures of peripheral blood lymphocytes from sheep and dogs and in mouse spleen cell cultures. Nylon wool non-adherent, T cell enriched fractions of lymphocytes from both mice and horses were stimulated by the S. vulgaris larval mitogen while no proliferation was observed in cultures containing ny...
Dyer RM, Liggitt HD, Leid RW.A device was constructed from an equine nasogastric tube, polyethylene tubing, and a 3-way stopcock and used to lavage the lungs of anesthetized ponies. The technique was safe and atraumatic in that 6.4 to 19.7 X 10(7) purified alveolar macrophages were removed from the lungs without harm to the ponies or contamination of the samples with blood. Studies of these highly purified cell suspensions revealed a mean viability of 85% as assessed by eosin dye exclusion with a mean recovery (+/- SD) of 12.5 +/- 4.8 X 10(7) pulmonary alveolar macrophages/pony.
Dyer RM, Leid RW.Isolated equine alveolar macrophages were shown to generate a luminol-dependent light response when challenged with a phagocytic stimulus. The chemiluminescent response was not detected with luminol prepared at 1.0 x 10(-5) or 1.0 x 10(-4) molar concentrations, but was readily quantitated when used at a 1.0 x 10(-3) molar concentration. Challenge of the alveolar macrophages with latex particles or with equine IgG-coated sheep red blood cells elicited the luminol-dependent light response, whereas unchallenged equine alveolar macrophages or those challenged with unopsonized erythrocytes failed t...
Dyer RM, Leid RW.Isolated equine alveolar macrophages obtained by bronchopulmonary lavage of four live ponies demonstrated surface receptors for equine IgG, equine IgM, and complement-coated sheep red blood cells, but not equine IgM or complement-coated erythrocytes alone. In addition, demonstration of IgG receptors was found to depend on the level of erythrocyte sensitization and could not be demonstrated by red blood cell rosetting techniques at low levels of sensitization. Demonstration of receptors for equine complement by red cell rosetting techniques required the presence of both IgM antibody and serum d...
Tablin F, Weiss L.The capacity of the equine spleen to store and rapidly release as much as half the circulating blood volume after adrenergic stimulation depends upon the size of the spleen, its muscular capsule, and the distinctive structure of its red pulp. The unit, or lobule, of red pulp is a cylinder of pulp spaces organized in a reticular meshwork, supplied by a peripheral ring of arterial capillaries, and drained by a central venule. Reticular cells, which make up the meshwork of the pulp, contain an extraordinarily large complement of microfilaments and intermediate filaments and are richly innervated ...
Brownlow MA.Cells in the peritoneal fluid from 179 horses were examined in Giemsa stained preparations using light microscopy. Mononuclear phagocytes were a common cell type observed in normal fluids. In the absence of stimulation they were morphologically similar to the peripheral blood monocyte and the unstimulated mesothelial cell. In acute inflammatory effusions their proportion decreased significantly but, as the condition resolved, monocytes began to migrate into the cavity gradually becoming more numerous, transforming into larger macrophages and assuming an increasing phagocytic role. They were of...
Shively MA, Banks KL, Greenlee A, Klevjer-Anderson P.Equine infectious anemia is a chronic disease of horses caused by a nononcogenic retrovirus. Studies were undertaken to determine the types of cells involved in the in vitro lymphoproliferative response to viral antigens and the dynamics of this reaction. It was observed that reactive lymphocytes were present at unpredictable times in the peripheral blood of infected horses. This reaction was shown to be specific for the interaction of equine infectious anemia virus and T lymphocytes. Enriched B-lymphocyte populations did not divide when exposed to equine infectious anemia virus. Macrophages w...
Patel JR, Edington N, Mumford JA.Subtype-1 isolates of Equine herpesvirus-1 (EHV-1) from a quadriplegic horse and from an aborted foetus were compared with each other and with a subtype-2 respiratory isolate. All 3 isolates were detected in the epithelium and macrophages of the respiratory tract. Both the paresis and foetal subtype-1 isolates replicated in the epithelium of the ileum and this correlated with the recovery of virus from faeces in vivo. The paresis subtype-1 isolate also had a predelection for vascular endothelial cells, particularly in the nasal mucosa, but also in the lungs, central nervous system, adrenal and...
Leishman D, Miller RB, Doig PA.The density of uterine glands, height of surface epithelium, numbers of hemosiderin laden macrophages, inflammatory cells and layers of periglandular fibrosis were evaluated in uterine biopsies from 40 mares. These features were found to be highly variable in normal equine endometrium. Minor pathological changes appeared to be masked by this normal variability. Atrophy of uterine glands was recognized in mares which had been barren for more than three years. No significant differences were found between barren and normal mares in the height of epithelium, number of hemosiderin laden macrophage...
Silver IA.Wound healing is part of the normal general repair process of the body. Its efficient completion depends on many factors, some physical, eg, pH, oxygen tension and tissue tension, and some biological, eg, cell-cell interaction and feedback of extracellular matrix on to the cells which produce it. The factors which affect healing are discussed and failures and anomalies in the process described. New techniques which may improve the quality of healing in specialised tissues are explained. Recent research on wound healing has concentrated on the role of the different cell types in the process and...
Zink MC, Johnson JA, Prescot JF, Pascoe PJ.The in-vitro interaction of Corynebacterium equi and foal alveolar macrophages was examined qualitatively and quantitatively using cells collected by sequential bronchoalveolar lavage at 2-week intervals from birth until 14 weeks of age. Total and differential counts were performed on the recovered cells. Macrophages were identified using the non-specific esterase strain. Cultures of the alveolar macrophages were challenged with C. equi suspensions and the process and extent of ingestion was examined by light and electron microscopy. Few macrophages were recovered from the lungs of foals less ...
Anderson LW, Banks KL.Equine macrophages were obtained from female Shetland ponies by injection of Escherichia coli lipopolysaccharide through the lactiferous ducts of the mammary gland. After 6 to 11 days, balanced salt solution was injected into the mammary gland to wash out accumulated cells. Harvested cells contained a mixture of macrophages, lymphocytes, and neutrophils, with the majority of the cells of mononuclear type. In culture, cells adherent after 24 hours were characterized as macrophages by morphologic features, nonspecific esterase staining, and by the presence of complement and immunoglobulin recept...
Dutta SK, Campbell DL.Equine macrophages from the mammary glands of a yearling filly and an 18-year-old barren nonlactatind mare formed cell monolayers in continuous cultures. There was absence of viral cytopathic effect (CPE) in early cell culture passages. The cells from the early cell culture passages having no CPE failed to show evidence of virus or viral antigen by electron microscopic and immunofluorescence studies. Foci of CPE first appeared in the monolayer cell cultures from the filly and the mare in the 3rd and the 4th serial passages respectively, and the CPE increased on subsequent serial passages. Equi...
Schumacher HR.The normal synovial membrane as seen by electron microscopy is bordered by one to three layers of lining cells that include some with phagocytic function, others rich in endoplasmic reticulum for protein synthesis and additional cells with mixed properties. Lining cells with prominent Golgi apparatus probably produce the synovial hyaluronic acid. The synovial matrix contains collagen and mucopolysaccharide. It offers little barrier to diffusion of most materials. Superficial capillaries and venules are fenestrated and presumably allow rapid exchange of fluid and electrolytes. Deeper venules ha...
Platt H.A series of 10 haemorrhagic polyps of the equine nasal cavity is described. The lesions show haematoma formation, abundant haemosiderin in macrophages and giant cells, and organising fibrous tissue. In one case, angiomatoid lesions were observed in the mucous membrane of the paranasal sinuses and it is suggested that some haemorrhagic nasal polyps may originate from pre-existing haemangiomatous areas in the respiratory mucosa.
Duncan JL, Pirie HM.The clinical signs, pathology and clinical pathology associated with single experimental infections of Strongylus vulgaris in worm-free pony foals are described. The major clinical signs which became apparent in the infected foals during the first three weeks were pyrexia, anorexia, dullness and abdominal pain. Within the first two weeks of infection lesions were confined to the intestine and terminal branches of the intestinal arteries and consisted of mucosal, submucosal and serosal haemorrhage together with arteritis of submucosal and serosal arteries and also a marked inflammatory reaction...
Butler J, Rydell NW, Balazs EA.Twelve horses with traumatic arthritis were treated with intraarticular injection of hyaluronic acid mixed with cortisone and the results compared with 6 horses treated only with cortisone. There was a significantly better improvement in the group injected with a mixture of hyaluronic acid and cortisone. Further studies have given the same results in traumatic arthritis in horses if hyaluronic acid alone is injected. After injection of hyaluronic acid a large number of granulated monocytes appeared in the synovial fluid, but no inflammatory signs were observed. It is possible that this macroph...
Equine recurrent uveitis serves as a spontaneous model for human autoimmune uveitis. Unpredictable relapses and ongoing inflammation in the eyes of diseased horses as well as in humans lead to destruction of the retina and finally result in blindness. However, the molecular mechanisms leading to inflammation and retinal degeneration are not well understood. An initial screening for differentially regulated proteins in sera of uveitic cases compared to healthy controls revealed an increase of the alternative pathway complement component factor B in ERU cases. To determine the activation status ...
Fegraeus K, Riihimäki M, Nordlund J, Akula S, Wernersson S, Raine A.Single-cell RNA sequencing (scRNA-seq) is a valuable tool for investigating cellular heterogeneity in diseases such as equine asthma (EA). This study evaluates the HIVE™ scRNA-seq method, a pico-well-based technology, for processing bronchoalveolar lavage (BAL) cells from horses with EA. The HIVE method offers practical advantages, including compatibility with both field and clinical settings, as well as a gentle workflow suited for handling sensitive cells. Our results show that the major cell types in equine BAL were successfully identified; however, the proportions of T cells and macropha...
Arnade H, Ivie IE, Gordon J, Peroni JF.To evaluate the feasibility of short-term 3-D tissue culture in maintaining the structure and function of equine synovial explants and demonstrate that day 4 explant characteristics were not significantly different from day 0. We hypothesized that a 4-day culture period in 3-D explant culture would not significantly disrupt synovial tissue health and function compared to baseline measurements. Unassigned: Synovial explants (n = 24/horse) from healthy carpal joints of 5 horses were cultured in 12-well plates using tissue-stabilizing agar rings. Explants were evaluated in triplicate or quadrupli...
Conley HE, Davis KU, Adler KB, Lavoie JP, Sheats MK.Asthma is a chronic inflammatory airway disease that affects millions of people worldwide. Horses develop asthma spontaneously and serve as a relevant model for multiple phenotypes and endotypes of human asthma. In horses with equine asthma (EA), environmental organic dust triggers increased inflammatory cytokines, excess airway mucus, reversible bronchoconstriction, and airway inflammation. In horses with severe EA (sEA), lower airway inflammation is invariably neutrophilic, making sEA a potential model for severe neutrophilic asthma in humans. Alveolar macrophages (AM) and airway neutrophils...
B B, G M, L G, G A, B B, T F, A G, D B, A K, G T, G S, A B, M F, L R.Equine penile tumors are common in horses and are often related to infection with equine papillomavirus type 2 (EcPV2). This study investigated the immune cell infiltrate (ICI) of these tumors in horses, focusing on the role of EcPV2. Using multiplex immunohistochemistry (mIHC) for CD3, CD20, and IBA-1 and immunohistochemistry (IHC) for FoxP3, 27 horses with papillomas (5/27), in situ carcinomas (CISs) (3/27), and squamous cell carcinomas (SCCs) (19/27) were evaluated. Eighteen cases tested positive for EcPV2 by either or both in situ hybridization (ISH) and polymerase chain reaction (PCR) (18...
Kang H, Lee GKC, Bienzle D, Hammermüller J, Arroyo LG, Lillie BN, Beeler-Marfisi J.Macrophage populations in the lung, including resident alveolar macrophages (AMs) and recruited monocyte-derived macrophages (MDMs), recognize the inhaled particulates in barn dust that cause severe equine asthma and orchestrate an immune response though the cytokines they produce. Despite their importance, the specific contributions of these macrophage subsets to lower airway inflammation remain poorly understood. This exploratory in vitro study investigated the likely contributions of AMs and MDMs from healthy horses to the early inflammatory response using RNA-seq. If biologically importan...
Chaimbeul SF, Rodrigues NNP, Thurston DD, Scoggin KE, Janes J, Jacobs CA, MacLeod JN, Stone AV, Menarim BC.Synovitis resolution is critical for joint homeostasis and prevents the progression of osteoarthritis (OA). Treatments like NSAIDs and intra-articular corticosteroids relieve symptoms by blocking pro-inflammatory mediators, but also impair the production of pro-resolving mediators, contributing to the likelihood of chronic synovitis. PPARγ signaling is an essential mechanism of synovitis resolution, which is decreased in OA tissues. To evaluate the potential of PPARγ agonists to promote pro-resolving pathways, equine macrophages cultured in autologous, normal, or inflamed synovial fluid ( = ...
Meeremans M, Devriendt B, Bairiot S, Van Poucke M, Peelman L, Demeyere K, Meyer E, Van Vlierberghe S, De Schauwer C.Macrophages play key roles in tissue homeostasis and regeneration-associated inflammation. Unlike humans, a reliable protocol to obtain and polarise equine monocyte-derived macrophages is lacking. In this study the polarisation of equine macrophages, derived from CD172a peripheral blood monocytes is described. After differentiation, IFN-γ/LPS or IL-4 were used to induce pro- and anti-inflammatory phenotypes, respectively. Evaluation criteria included morphology, mRNA (RT-qPCR) and protein expression (flow cytometry, immunofluorescence), nitric oxide and arginase production, cytokine secretion...
Zamith Cunha R, Gobbo F, Morini M, Salamanca G, Zanoni A, Bernardini C, Gramenzi A, Chiocchetti R.Evidence suggests that the endocannabinoid system (ECS) is crucial for regulating inflammation, cell proliferation and pain. The ECS is composed of cannabinoid receptors such as type 1 (CBR1), type 2 (CBR2) and GPR55, endocannabinoids and enzymes. Proteins of ECS have previously been localized in the epidermal cells of the horse hooves. Given the physio-pathological role and cellular distribution of the ECS across species, the authors hypothesized that cannabinoid receptors are expressed within the inflammatory cells, fibroblasts and endothelial cells of the equine hoof laminae, going beyond t...
Moroni R, Fanelli D, Maltinti S, Orefice M, Rota A, Camillo F, Melanie P, Cantile C, Miragliotta V, Pirone A, Lazzarini G, Passamonti F, Marmorini P....Equine persistent breeding-induced endometritis can lead to chronic uterine inflammation and fibrosis, reducing fertility. Intrauterine ozone (O₃) has recently been proposed as a potential treatment for mares unresponsive to conventional therapies. This case series describes O₃ treatment in eleven mares barren for at least one year despite multiple inseminations attempts. During the first oestrous cycle, low-volume uterine lavage and endometrial biopsy were performed, followed by 3 consecutive days of intrauterine O₂-O₃ gas insufflation. In the subsequent cycle, both procedures were re...
Sugimoto K, Nakamura J, Deng D, Hirano E.Indoxyl sulfate (IS) is a dietary metabolite of tryptophan that is produced in the liver. It is a uremic toxin that facilitates the progression of chronic kidney disease (CKD). We previously observed that equine placental extract (ePE) inhibited IS synthesis in an inhibition assay using the liver S9 fraction. Unassigned: This study was designed to investigate the effects of ePE on adenine-induced renal failure in mice at the histological and molecular levels to understand the mechanism of action of ePE. Unassigned: We assessed this effect through biochemical and histological analyses using a...
Hananeh W, Al Rukibat R, Hammad H, Mukbel R.Leishmaniosis is an endemic parasitic infection in Jordan and the Middle East. Despite the endemicity of leishmaniosis in Jordan and frequently reported humancases, no singleclinical case has been documented in animals throughout the country. This report documents the first two animal Leishmania cases in two different animal species with a current literature review. Cutaneous leishmaniosis was diagnosed in an adult horse that presented with multiple variably sized skin nodules, some of which ulcerated. Visceral leishmaniosis was diagnosed in a stray dog. Cytological, histopathological, and mol...
Yerlikaya Z, Miranda-CasoLuengo R, Jahns H, Byrne O, Meijer WG, Mulcahy G, Walshe N.Cyathostomins are the most prevalent and currently considered the most pathogenic gastrointestinal nematodes in horses. Their life cycle includes an encystment phase within the large intestinal mucosa, where up to 90 % of the total worm burden resides. Clinical disease ranges from chronic protein-losing enteropathy to acute, sometimes fatal, typhlocolitis. Despite their significance, the ecological interplay between cyathostomins, the host immune response, and the gut microbiota remains poorly understood. To our knowledge, this is the first study to investigate these interactions at the mucos...
Huguet A-S, Gourbeyre O, Bousquet-Mélou A, Ferran AA, Lallemand EA. is an opportunistic intracellular pathogen responsible for severe respiratory infections in foals, requiring prolonged antibiotic treatment. Despite its susceptibility to multiple antibiotics, the eradication of intracellular remains challenging due to its ability to persist and survive within alveolar macrophages. This study aimed to assess the extracellular and intracellular activity of rifampicin, doxycycline, and four macrolides against while assessing current methodologies used to differentiate intracellular and extracellular bacteria. We found that the removal of extracellular wit...
De Ciucis CG, Fruscione F, Dell'Anno F, Zinellu S, Giaconi E, Loi S, Columbano N, Franzoni G, Razzuoli E.Toll-like receptors (TLRs) are a group of pattern recognition receptors (PRRs), that play critical roles in initiating host immune defenses. TLR-2 agonists can activate innate immune cells and thus are attracting increasing attention as prophylactic and/or therapeutic agents against infectious diseases or in cancer immunotherapy. In this work, the impact of three synthetic diacylated lipopeptides (Mag-Pam2Cys_P48, MagPam2Cys_P80, and Mag-Pam2Cys_MAG1000) on equine monocyte-derived macrophages (moMΦ) phenotype and functionality was thoroughly investigated. MoMΦ were generated from circulatin...
Liso G, Winter K, Triebe TJ, Ulrich R, Brehm W, Wagner B, Schnabel CL, Troillet A, Roth SP.Synovial macrophages' role in equine osteoarthritis (OA) is not well understood, despite horses being a model for human degenerative joint disorders. Equine synovial macrophages' characterization is limited and age-related changes are not described. This study aimed to evaluate surface marker distribution and expression from potential synovial tissue macrophages in foals, adult non-affected, and OA-affected horses. Unassigned: Surface markers (CD14, CD16, CD206) were quantitatively evaluated on dorsal villous synovial biopsies from the metacarpophalangeal joint of foals (F), non-affected (cont...
Jagannathan V, Leeb T, Gerber V, Sage SE. Bulk RNA sequencing (RNA-seq) averages signals across heterogeneous cell populations. Computational deconvolution methods aim to infer cell type composition and cell type-specific gene expression from bulk data, but their performance in equine samples has not been evaluated. In this study, we assessed the ability of computational deconvolution to recover cellular composition and differential expression signals in bronchoalveolar lavage fluid (BALF) from horses with severe equine asthma (SEA) and controls (CTL). Cryopreserved BALF samples from six SEA and five CTL horses previously analyzed b...
Chen K, Du C, Duan Y, Guo K, Liu D, Wang F, Wang X, Wen Y.Macrophage phenotypic adaptation critically regulates inflammatory balance during infection; however, progress in equine immunology has been limited by a lack of specific tools for standardized identification. To address this gap, we established a reliable, antibody-based detection method for characterizing equine macrophage M1-like and M2-like marker profiles. After initially validating canonical marker genes via qPCR, we developed specific monoclonal antibodies targeting the differentially expressed surface proteins CD80 (M1-like) and CD163 (M2-like). These novel antibodies enabled the creat...
Martinoli G, De Biase D, Ressel L, Brunetti B, Avallone G, Grillini A, Franceschini T, Fiorentino M, Sarli G, Bacci B.This study investigates the molecular and immune characteristics of equine ocular squamous cell carcinoma (eoSCC). Immunohistochemistry (IHC) and next-generation sequencing (NGS) were used to detect protein expression and TP53 mutations, respectively. T lymphocytes (CD3+), regulatory T cells (FoxP3+), B lymphocytes (CD20+), and macrophages (IBA-1+) were quantified. A total of 29 cases of eoSCC were evaluated, consisting of 3/29 carcinomas in situ (CISs) and 26/29 squamous cell carcinomas (SCCs). p53 positivity by IHC was detected in 19/29 cases while by NGS, 21 TP53 mutations were found in 13/...
Barbazanges P, Richard EA, Debonnaire C, Le Digarcher G, Lemonnier LC, Toquet MP, Couroucé A.Guttural pouch (GP) disorders are clinically important in horses, yet the relationship between endoscopic findings and GP cytology remains poorly defined. Objective: To establish reference cytological values for GP lavage fluid in horses and to investigate associations between inflammatory cytology and endoscopic findings. Methods: Asymptomatic racing horses sampled in the field and horses referred for investigation of respiratory disorders. Methods: Prospective cross-sectional study. Horses underwent clinical examination, upper airway endoscopy, and bilateral transendoscopic GP lavage. A GP i...
