The immune response in horses involves a complex network of cells, tissues, and molecules that work together to protect the animal from pathogens and other harmful agents. This process includes both innate and adaptive immune mechanisms. Innate immunity provides the first line of defense and involves components such as physical barriers, phagocytic cells, and the complement system. Adaptive immunity, on the other hand, is characterized by the activation of lymphocytes and the production of antibodies, which provide a targeted response to specific antigens. Key components of the equine immune system include T cells, B cells, and various cytokines that facilitate communication between immune cells. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, regulation, and implications of immune responses in equine health.
Todd EW.Antiproteinase sera were prepared by immunizing horses with filtrates from a selected strain of group A streptococcus. This strain, which produced high titred proteinase but no erythrogenic toxin, was selected from forty-two strains of group A streptococci which produced varying amounts of proteinase. A few strains belonging to groups B, C, and G were also tested; they were all proteinase-negative. Methods are described for titrating streptococcal proteinase in crude culture filtrates and for measuring the antiproteinase activity of serum. The antiproteinase titres of sera from immunized horse...
Olitsky PK, Harford CG.Young (12 to 15 day old) mice are approximately as susceptible to the virus of equine encephalomyelitis, Eastern or Western strain, when it is given intraperitoneally as are adult mice when the virus is injected intracerebrally. With this susceptibility by the intraperitoneal route as a basis, the injection of immune serum-virus mixtures intraperitoneally was found to result in protection in dilutions which give rise to infection after intracerebral inoculation. The difference of protective power by the two indicated routes was shown not to depend on the amount of inoculum nor on the age of th...
Inada R, Ido Y, Hoki R, Ito H, Wani H.Horses immunized with cultures of Spirochaeta icterohaemorrhagiae yield an immune serum having therapeutic properties. With rare exceptions the serum destroys completely the spirochetes contained in the circulating blood. The development of antibodies is promoted by the serum injections. The number of spirochetes in the organs is reduced by the treatment. Secondary manifestations due to the serum are slight and disappear promptly. The ultimate effects of the serum treatment on the symptoms and final outcome of the disease have still to be determined.
Smith T.The foregoing and earlier data taken together demonstrate that an active immunity lasting several years can be produced in guinea-pigs, by the injection of toxin-antitoxin mixtures which have no recognizable harmful effect either immediate or remote. They also show, what might have been anticipated, that under the same conditions mixtures which produce local lesions and which, therefore, contain an excess of toxin produce a much higher degree of immunity than the neutral mixtures, and that an excess of antitoxin reduces the possibility of producing an active immunity, and may extinguish it alt...
Although equine herpesvirus myeloencephalopathy (EHM) is a relatively uncommon manifestation of equine herpesvirus-1 (EHV-1) infection, it can cause devastating losses during outbreaks. Antemortem diagnosis of EHM relies mainly on the molecular detection of EHV-1 in nasal secretions and blood. Management of horses affected by EHM is aimed at supportive nursing and nutritional care, at reducing central nervous system inflammation and preventing thromboembolic sequelae. Horses exhibiting sudden and severe neurologic signs consistent with a diagnosis of EHM pose a definite risk to the surrounding...
Respiratory diseases are a major cause of morbidity and mortality in the horses of all ages including foals. There is limited understanding of the expression of immune molecules such as tetraspanins and surfactant proteins (SP) and the regulation of the immune responses in the lungs of the foals. Therefore, the expression of CD9, SP-A and SP-D in foal lungs was examined. Results: Lungs from one day old (n = 6) and 30 days old (n = 5) foals were examined for the expression of CD9, SP-A, and SP-D with immunohistology and Western blots. Western blot data showed significant increase in the...
Fifteen horses harboring naturally acquired, patent Parascaris equorum and Oxyuris equi infections were equally allotted to 3 treatment groups given (1) injectable vehicle; (2) injectable ivermectin at the dose rate of 200 microgram/kg of body weight; and (3) injectable ivermectin at the rate of 300 microgram/kg. All treatments were given IM in the neck. All animals were killed 14 days after treatment and examined for the targeted nematodes. Regardless of dose rate, ivermectin proved 100% effective in the removal of adult O equi and P equorum infections. Levels of immature P equorum were decre...
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 ...
Zhou B, Chen K, Liang H, Qi T, Guo X, Wen Y-J, Du C, Wang X.Equine arteritis virus (EAV) is a positive-sense, single-stranded RNA virus that belongs to the family , which also includes porcine reproductive and respiratory syndrome virus (PRRSV). EAV is the causative agent of equine viral arteritis (EVA), an economically important systemic, reproductive, and respiratory disease of equids. EAV infection triggers host innate immunity, yet the precise strategies employed by the virus to evade immune defenses and achieve productive infection are poorly characterized. In this study, it was observed that EAV infection can induce a cellular IFN response; howev...
Zhou Y, Ren W, Zeng Y, Wang J, Meng J, Yao X, Zhai M.Kazakh horses are typical seasonal breeders, and ovarian activity is markedly reduced during the non-breeding period. Hormonal stimulation can induce ovarian functional responses during seasonal anestrus; however, the early ovarian transcriptional changes associated with this response remain incompletely understood. In this study, ovarian transcriptome sequencing was performed in 12 Kazakh mares examined during the seasonal anestrous period. The mares were classified into a non-hormonally stimulated seasonal quiescent group (DB, = 6) and a hormone-induced ovarian activation group (DY, = 6) f...
Dembek K.Critical illness-related corticosteroid insufficiency is a transient dysfunction of the hypothalamic-pituitary-adrenal axis, leading to inadequate cortisol responses during severe stress from endotoxemia and sepsis in horses and foals. This condition is associated with poor outcomes, and its diagnosis is complicated by interindividual variability in cortisol response. Recent advances in dynamic testing and point-of-care hormone tests offer promise for better assessment and treatment, enabling more precise steroid replacement therapy in affected equine patients.
Ammons D, Chow L, Goodrich L, Barrett M, Nelson B, Impastato R, Stoneback JW, Dow S, Pezzanite LM.Define temporal cellular changes following joint injury using single-cell RNA sequencing in experimental equine posttraumatic osteoarthritis (PTOA). Unassigned: PTOA was induced in 4 Quarter Horses (3 to 5 years) via carpal osteochondral fragmentation and high-speed treadmill exercise. Synovial fluid (SF) cells and synovium were sampled over 18 weeks (November 2023 to April 2024). Single-cell suspensions were processed (10x Genomics Chromium iX), then aligned to the equine genome (Cell Ranger). Downstream analysis was completed in the R Seurat package. Differential gene expression (log2[fold c...
Williams Louie E, Cercone M, Delvescovo B, Chevalier J, Mitchell K.Horses with endotoxemia have variable myocardial function, but little is known about the severity or persistence of myocardial dysfunction (MD). Objective: Horses with experimentally induced endotoxemia have systolic and diastolic MD. Methods: Twelve systemically healthy horses. Methods: Horses were given Escherichia coli lipopolysaccharide 30 ng/kg over 60 min. Echocardiography and cardiac troponin I (cTnI) measurements were performed at baseline, 1, 3, and 5 h post-endotoxin. Fluid therapy (10 L), polymyxin B (6000 IU/kg), and flunixin meglumine (1.1 mg/kg) were administered intravenou...
Hunyadi LM, Hyde SC, Sundman EA.The role of inflammation, allergy, and air quality in the pathogenesis of equine asthma has not yet been fully elucidated. Objective: To evaluate serum inflammatory cytokines, intradermal skin testing (IDT), and air quality in asthmatic horses. It was hypothesized that there would be an association between environmental allergies and poor air quality with asthma. Methods: 52 client-owned horses with clinical signs consistent with asthma were enrolled in this cross-sectional study. Horses were diagnosed with asthma based on the results of bronchoalveolar fluid (BALF) cytology. Blood samples wer...
Styková E, Mudroňová D, Gancarčíková S, Žert Z, Kačírová J, Valocký I.Chronic equine proliferative pododermatitis (canker) is a hypertrophic hoof disease characterized by excessive proliferation of horn-producing tissues resulting from dyskeratosis of keratinocytes. Since its etiology remains unknown, this study investigated potential etiological agents and evaluated biochemical and immunological profiles. Ten horses with hoof canker and ten healthy controls of the Norik of Muran breed were included. Dermatophytes and bovine papillomavirus 1 and 2 (BPV 1/2) were not detected. Candida glabrata was the most frequently identified species in both affected and health...
Korac L, St George L, McCrae P, MacNicol J, Golestani N, Souccar-Young J, Karrow N, Cánovas Á, Avison A, Pearson W.Recently, a synovitis model using 75 ng intra-articular recombinant equine interleukin-1 (reIL 1β), showed promise for inducing a mild, self-limiting inflammatory response without overtly altering upper-body movement asymmetry in = 3 horses. This study aimed to evaluate the effect of this 75 ng reIL-1β model on gait biomechanics and synovial fluid (SF) inflammatory, pro-resolution, and cartilage turnover biomarkers in a larger equine sample. SF samples were collected from the left intercarpal joint of = 11 horses at baseline and at 6- and 12-hours following 75 ng reIL-1β injection and...
Luedke L, Clark A, Hendrickson DA, Bass L, Kawahisa-Piquini G, Impastato R, Sabino I, Chow L, Dow S, Pezzanite LM, Griffenhagen GM.Liposomal local anesthetics have been shown to extend analgesia duration and improve pain scores dose-dependently in horses. Our objective was to assess concurrent impact on systemic inflammatory markers. Unassigned: 18 mares (age, 2 to 20 years) with normal ovarian anatomy were enrolled. Laparoscopic bilateral ovariectomies were performed standing with sedation. Local analgesia was: 80 mL bupivacaine hydrochloride (BHCl; n = 6), 30 mL 0.75% BHCl + 20 mL (low-dose) liposomal bupivacaine (LB) expanded to 80 mL with saline (LB20, n = 6), or 30 mL 0.75% BHCl + 40 mL (high-dose) LB expanded to equ...
Alleaume C, Laloy E, Dupuis-Tricaud MC, Kuk N, Kariya E, Keck N, Depaquit J, Lachaud L, Ravel C.In this study, we describe the first documented cases of equine cutaneous leishmaniasis caused by Leishmania (Mundinia) martiniquensis in France and provide clinical and parasitological data relevant for the recognition of this emerging infection in horses. Three horses presenting localized cutaneous lesions were diagnosed with L. martiniquensis infection in different regions of France without spatial or temporal clustering. Lesions were clinically nonspecific and initially compatible with common equine dermatological conditions, including sarcoid-like tumors. Histopathological examination rev...
Crook RA, Branch AE, Kapadia CL, Klinglesmith BA, Hatzel JN, Sones JL, Fedorka CE.Successful establishment of pregnancy requires maternal immune tolerance to paternal antigens introduced by insemination. Regulatory T cell (Treg)-associated responses are thought to play a central role in this process, whereas pro-inflammatory T helper 1 (Th1) responses may disrupt pregnancy success. In other species, seminal plasma (SP) has been shown to modulate maternal immune adaptation; however, this relationship remains poorly defined in mares, where SP is frequently reduced during routine breeding practices. The objectives of this study were to (1) characterize temporal changes in syst...
Leal M, Silva E, Alpoim-Moreira J, Pinto-Bravo P, Rebordão MR, Quaresma M, Jalali B, Molcan T, Szóstek-Mioduchowska A, Skarzynski D, Ferreira-Dias G.Equine persistent post-breeding endometritis may lead to endometrosis, characterized by excessive fibrosis, which is a major cause of subfertility/infertility. Endometrial proteomic changes induced by endometritis, when associated with fibrosis, were investigated to identify the biological processes (BP) involved. Cyclic mares´ endometrial biopsies were histologically classified (Kenney and Doig's) as: category IIA (n = 5), category IIA with endometritis (IIA-E; n = 4), category IIB (n = 5), or category IIB with endometritis (IIB-E; n = 5). Proteome was assessed by LC-MS/MS. I...
Akula S, Zhang B, Riihimäki M, Wernersson S, Raine A.The skin serves as the primary barrier tissue in horses and is frequently affected by immune-mediated dermatological conditions, most notably insect bite hypersensitivity (IBH). Yet, the cellular composition and transcriptional landscape of normal equine skin have never been characterized at single-cell resolution. Here, we present a single-cell RNA sequencing dataset of healthy equine skin comprising 85,574 high-quality transcriptomes from two horses, with one skin biopsy collected from each horse, divided into two portions for independent processing via manual or automated tissue dissociatio...
Miranda RPDR, de Miranda BA, Aranha AB, Gomes Ramos MFB, Oliveira EP, Dallago BSL, Adorno J, Macêdo IL, Castro MB, Campebell RC.Skin wounds are common in horses due to species-specific behavioral responses. Equine skin morphology, vascularization, and inflammatory responses to wounds are comparable to those in humans, supporting the translational relevance of equine wound-healing studies. Investigating biomaterials such as tilapia and frog skin may improve wound management. This study demonstrated that sterilized tilapia and frog skin exhibit promising wound-healing properties. Unassigned: Macroscopic, microscopic, and thermographic aspects of second-intention wound healing were compared in six horses with surgically i...
Cappai MG, Sarah M, Alice S, Andrea T, Giampaolo B, Raffaele C.Breeding stallions are subjected to sustained seasonal metabolic, endocrine, and immune demands requiring systemic energy engagement. Prospective longitudinal data in the same individuals are limited. Objective: To screen adaptive responses of breeding stallions of clinical relevance through longitudinal characterisation of temporal changes across the mating season and negative photoperiod: (i) health and nutritional status; (ii) oxidative status and immune modulation; and (iii) metabolic and endocrine biomarkers as correlates of reproductive potential. Methods: Prospective longitudinal observ...
Charbonnel A, Thorin C, Allain S, Guicheux J, Boutet MA, de Fourmestraux C.Endoscopy and synovial membrane histology are complementary modalities for evaluating synovial inflammation. Cytokine involvement in non-septic arthritis is well documented but remains poorly characterized in septic synovitis. Objective: This study aimed to characterize the inflammatory cytokine profile associated with septic and non-septic synovitis and assess correlations among endoscopic, histological, and synovial fluid biomarker findings. Methods: Three groups were defined: horses undergoing elective or therapeutic endoscopy (Group 1, n=26), horses with confirmed septic synovitis (Group 2...
Matas-Quintanilla M, Castillo C, Whitacre L, Ipharraguerre IR, Gutiérrez-Panizo C, Hernández J, Gutiérrez AM.Gastric ulceration is common in horses and remains challenging to diagnose, as gastroscopy is the gold standard. This study aimed to characterise the salivary and serum protein changes associated with a feed-deprivation protocol. Eight horses underwent this protocol, and gastric lesions were assessed by gastroscopy at the end of the experimental period. Saliva and blood samples were collected pre- and post-protocol, and pooled samples from each biological fluid and condition were analysed by two-dimensional gel electrophoresis to compare protein profiles. Fifteen salivary and five serum protei...
Tóth J, Buijs L, Lorenz R, Bakos Z.Eosinophilic keratoconjunctivitis (EKC) is an inflammatory eye disease of horses with an unknown cause and suspected immune-mediated pathogenesis. This single-center retrospective case series included 114 horses (163 affected eyes) examined at a German equine referral hospital from January 2012 to December 2020. Of these horses, 71 (62.3%) were Warmbloods, 77 (67.5%) were presented from July to September, and 49 (43.0%) had bilateral disease. The cornea was involved in 139 of 163 eyes (85.3%). During the study period, 114 EKC cases occurred among 5742 ophthalmology cases (2.0%), with an increa...
Røgild ER, Mármol-Sánchez E, Toft K, Hansen S, Cirera S.Equine asthma (EA) is a highly prevalent, chronic, inflammatory disease of the lower airways ranging from mild-to-moderate to severe clinical presentations. Diagnosis currently relies on bronchoalveolar lavage fluid (BALF) cytology, an invasive method associated with interobserver variability, which highlights the need for more reproducible approaches. MicroRNAs (miRNAs) are small noncoding RNAs involved in gene regulation. They are stable and readily detectable in body fluids and have shown promising results as biomarkers in human asthma. The aim of this pilot study was to characterize miRNA ...
Wierzbicka M, Minett D, Pawliński B, Siemieniuch-Tartanus M.Equine asthma is increasingly recognised as a biologically heterogeneous syndrome in which similar clinical manifestations may arise from distinct molecular mechanisms. Although clinical phenotypes have substantially improved disease classification, increasing evidence indicates that molecular endotypes more accurately reflect the biological mechanisms underlying disease heterogeneity. This review summarises current knowledge regarding the pathophysiological mechanisms of equine asthma, with particular emphasis on inflammatory pathways, molecular endotypes, genetic susceptibility, airway remod...
Apaoblaza S, Albornoz A, Henriquez C, Quiroga J, Burgos RA, Moran G.Ivermectin has been reported to exert immunomodulatory effects on the innate immune system; however, the available evidence is contradictory, with both anti-inflammatory and, paradoxically, pro-inflammatory effects described depending on species, dose, and experimental context, while data specific to horses remain scarce. We hypothesised that ivermectin would exert a context-dependent immunomodulatory effect on equine leucocytes. To test this, total leucocytes isolated from six healthy horses were incubated with ivermectin (2 and 4 µg/mL) before stimulation with lipopolysaccharide (LPS) and n...
Källse A, Källberg M, Ström L.To evaluate long-term clinical outcomes, recurrence rates, and complications following photodynamic therapy (PDT) in horses with immune-mediated keratitis. Unassigned: Medical records of horses treated with PDT at the Swedish University of Agricultural Sciences Equine Clinic from May 2018 through October 2025 were reviewed retrospectively. Eyes with a clinical diagnosis of recurrent immune-mediated keratitis that had responded to immunosuppressive therapy and been subjected to PDT therapy were included. Infracyanine green was injected intrastromally, followed by irradiation with an 810-nm diod...
Leal M, Silva E, Alpoim-Moreira J, Rebordão MR, Quaresma M, Li J, Szóstek-Mioduchowska A, Skarzynski D, Ferreira-Dias G.Endometrosis, characterized by excessive endometrial fibrosis, is a major reproductive disorder that impairs fertility and remains a significant challenge in equine breeding. The molecular mechanisms underlying equine endometrosis are not fully understood. This study investigated endometrial proteomic changes induced by endometrosis to identify the biological processes (BP) and pathways involved. Cyclic mares' endometrial biopsies were categorized as category IIA (n = 5) or category IIB (n = 5), according to Kenney and Doig's classification. LC-MS/MS assessed the endometrial proteome, ...
Rajesh A, Harman RM, Van de Walle GR.Neutrophil chemotaxis and phagocytosis are critical for protection against bacteria, but can be compromised by methicillin-resistant Staphylococcus aureus (MRSA). MRSA can also circumvent macrophage surveillance by affecting polarization and reactive oxygen species (ROS) production. We previously demonstrated that the secretome of equine mesenchymal stromal cells (MSCs), comprised of all secreted bioactive factors and collected as conditioned medium (CM), reduces the growth of MRSA both in vitro and in vivo. This study aimed to determine if the equine MSC secretome has additional anti-MRSA pro...
