Topic:Immune Response
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.
Correlation between nuclear factor-kappaB activity in bronchial brushing samples and lung dysfunction in an animal model of asthma. Asthma is a chronic inflammatory disease of the airways, in which many inflammatory genes are overexpressed. Transcription factor, nuclear factor-kappaB (NF-kappaB), which is thought to control the transcriptional initiation of inflammatory genes, has been poorly investigated in asthma. In the present report, bronchial cells (BCs), recovered by bronchial brushing in healthy and heaves-affected horses (i.e., an animal model of asthma), were assessed for NF-kappaB activity. Small amounts of active NF-kappaB were present in BCs of healthy horses, whereas high levels of NF-kappaB activity was foun...
Actions and interactions of ADP, 5- HT, histamine and PAF on equine platelets. Platelets are thought to play a role in equine diseases such as acute laminitis and verminous arteritis and may be involved in allergic disease. Mediators implicated in the pathophysiology of these conditions activate platelets and responses may be enhanced by interactions between mediators. The present study compared platelet aggregation, thromboxane production and release of radiolabelled [(3)H]5- HT in response to 5- HT, histamine, ADP and PAF alone and in combination in vitro.PAF caused concentration-related aggregation, [(3)H]5- HT release and thromboxane production. In contrast, ADP caus...
Effect of single bouts of moderate and high intensity exercise and training on equine peripheral blood neutrophil function. The effects of single bouts of moderate (30 to 40 per cent VO(2)max) and high (115 per cent VO(2)max) intensity exercise on equine peripheral blood leucocyte function were evaluated by determining neutrophil phagocytosis and oxidative burst activity before and after treadmill exercise and training. Prior to all exercise tests, the possible effect of diurnal variation was evaluated in samples obtained from four resting horses. Subsequently eight horses underwent moderate and high intensity exercise protocols and then commenced a 17-week training period. High intensity exercise tests were repeat...
Equine vaccination. Equine infectious disease remains a constant and important threat to the health of domesticated horses. Vaccination plays a critical role in protecting against such disease, but at the present time the efficacy of some equine vaccination strategies is in doubt. The best strategy for resolving these concerns is an improved knowledge of the immunologic basis of successful vaccination, combined with the appropriate integration of effective vaccines into well-designed disease control policies.
Equine immunity to parasites. Helminths are among the most significant parasites of horses in developed countries. This article examines immune responses against helminth parasites and the implications that immunologic investigations have on vaccine development, improvement of diagnostic procedures, and disease eradication.
Immunodiagnostic testing in horses. Technologic advances in immunodiagnostic testing have enhanced our understanding of the pathogenesis of a broad array of diseases, including infectious diseases, immunodeficiency disorders, and immune-mediated disorders. If applied rationally, with an understanding of the questions the tests answer as well as the limitations that constrain their use, these tests can serve as valuable aids in the diagnosis and management of equine diseases.
Equine T-cell cytokines. Protection and pathology. The ultimate reason for better characterizing the immune response to infectious agents is the hope that this knowledge may lead to the development of better preventative or therapeutic measures. As more information becomes available, it becomes possible to incorporate these findings into the design of better vaccines and treatments. Likewise, attempts to either enhance or suppress specific helper T-cell responses may be required to control immunopathologic reactions. Although cytokine intervention in the clinical setting remains theoretic at this time, future manipulation based on the TH1/TH2 ...
Equine immunity to bacteria. The remarkable ability of the horse and other animals to prevent infection by most bacterial pathogens encountered is the result of a complex set of distinct but overlapping defense mechanisms. This article summarizes the current state of knowledge on innate and adaptive immunity to bacterial pathogens and reviews various ways in which some bacteria have evolved in order to evade components of the host response.
Secondary immunodeficiencies of horses. FPT of immunoglobulin in foals is the commonest form of acquired immunodeficiency in horses. FPT predisposes foals to bacterial infections and septicemia and easily is preventable and treatable if breeding farms and veterinarians are attentive to optimum foaling management practices. Other forms of acquired immunodeficiencies are uncommon in horses, although immune function may be transiently suppressed by a wide variety of drugs, infections, or other conditions. As immunologic testing becomes more sophisticated and more readily available to equine practitioners, acquired immunodeficiencies ar...
Inflammation in horses. After inflammation is initiated by detection of antigen, plasma components and activated leukocytes are concentrated at the inflammatory site. Cellular and chemical effectors of inflammation are focused on the offending antigen, usually resulting in its destruction and elimination. Activation of endogenous counter-regulatory systems damps down the inflammatory process and is the first stage of repair. In addition to local effects, the inflammatory focus may initiate a continuum of systemic acute phase responses ranging from the systemic inflammatory response syndrome (SIRS) to generalized immu...
Equine immunity to viruses. The identification of some of the adaptive immune responses to infection with equine viruses has been the first step toward rational immunoprophylactic design. Sufficient knowledge of infection-induced immunity and informed estimates of the requirements for long-term immunity for EIV have now been obtained. Thus, the future for inactivated EIV vaccines is promising now that new adjuvants have been applied to induce cellular immunity and safe methods have been designed to stimulate virus-neutralizing (VN) antibody at mucosal surfaces. Adenoviruses induce circulating VN antibody, the presence of...
Nitric oxide inhibits aggrecan degradation in explant cultures of equine articular cartilage. Arthroses are debilitating diseases of articular joints which result in erosion of the cartilage extracellular matrix. Nitric oxide (NO) is a major component of the inflammatory response, and has been implicated as a mediator of some of the effects of the proinflammatory cytokine, interleukin-1 (IL-1). In this study, we investigated the role of NO in the regulation of proteoglycan degradation in equine articular cartilage. NO fully mediated the suppressive effect of IL-1 on proteoglycan synthesis. However, NO was also antagonistic to proteoglycan degradation, irrespective of whether degradatio...
Immune responses in mice, cattle and horses to a DNA vaccine for vesicular stomatitis. Vesicular stomatitis (VS) virus causes an important clinical disease of cattle and horses in North America. In order for a vaccine to be useful in the control of VS, it must not only protect against disease, but allow ready differentiation of infected and vaccinated animals. In these studies, we evaluated neutralizing antibody responses in outbred mice, calves, and horses that received a DNA vaccine that expressed the glycoprotein (G) gene of VS New Jersey virus. The vaccine elicited antibody titers in individuals from each species, especially when two doses were administered, but the level of...
Uterine clearance and resistance to persistent endometritis in the mare. The objective of this article is to review the role of uterine defense mechanisms in natural resistance to chronic or persistent endometritis. A breakdown of uterine physical clearance mechanisms is currently believed to play a major role in susceptibility to persistent endometritis. Mares with increased susceptibility to persistent endometritis have impaired myometrial contractility in response to an acute inflammation, resulting in an accumulation of fluid and inflammatory products within the uterine lumen. The origin of this defect remains unknown. Recent studies have demonstrated that sper...
Hepatic abscesses in three horses. Hepatic abscesses were diagnosed in 3 adult horses. Two were < 4 years old and had evidence of concurrent immune-mediated conditions, including aseptic arthritis, immune-mediated thrombocytopenia, and immune-mediated anemia. Predisposing factors for hepatic abscess formation in these horses included prior abdominal surgery, proximal duodenitis/jejunitis, inflammatory bowel disease, and a penetrating foreign body in the large colon. Serum hepatic enzyme activities were within or slightly greater then reference limits in all 3 horses. The most pronounced and consistent abnormalities on CBC and s...
Tissue sites of persistent infection and active replication of equine infectious anemia virus during acute disease and asymptomatic infection in experimentally infected equids. Equine infectious anemia virus (EIAV) infection of horses is characterized by recurring cycles of disease and viremia that typically progress to an inapparent infection in which clinical symptoms are absent as host immune responses maintain control of virus replication indefinitely. The dynamics of EIAV viremia and its association with disease cycles have been well characterized, but there has been to date no comprehensive quantitative analyses of the specific tissue sites of EIAV infection and replication in experimentally infected equids during acute disease episodes and during asymptomatic ...
Possible mechanisms of mammalian immunocontraception. Ecological and conservation programs in ecosystems around the world have experienced varied success in population management. One of the greatest problems is that human expansion has led to the shrinking of wildlife habitat and, as a result, the overpopulation of many different species has occurred. The pressures exerted by the increased number of animals has caused environmental damage. The humane and practical control of these populations has solicited the scientific community to arrive at a safe, effective, and cost-efficient means of population control. Immunocontraception using zona pellu...
Immune cell populations in the equine corpus luteum throughout the oestrous cycle and early pregnancy: an immunohistochemical and flow cytometric study. Recent evidence indicates that the cells of the immune system and their large network of secretory products, or cytokines, play an active role in the ovary throughout the oestrous cycle. In the present study, immune cell populations (T and B lymphocytes, macrophages, granulocytes and eosinophils) and expression of major histocompatibility complex (MHC) class II were investigated in corpora lutea from mares in early (days 2-4), mid- (days 7-10) and late (days 12-14) dioestrus, the post-luteolytic phase (days 16-17) and early pregnancy. The number of T lymphocytes within the corpus luteum increa...
Immunity to equine influenza: relationship of vaccine-induced antibody in young Thoroughbred racehorses to protection against field infection with influenza A/equine-2 viruses (H3N8). Field outbreaks of influenza that occurred in vaccinated Thoroughbred racehorses in Newmarket in 1995 and 1996 were investigated by nucleoprotein ELISA and serology. Investigations showed that serum levels of vaccine-induced single radial haemolysis (SRH) antibody correlated closely with protective immunity against equine influenza and were consistent with observations made in previous experimental studies using nebulised aerosol challenge. In the second part of this study, antibody levels stimulated by vaccination were investigated to examine probable protection in high risk groups, such as y...
Influence of oral beta-alanine and L-histidine supplementation on the carnosine content of the gluteus medius. The aim of this work was to test the hypothesis that in vivo carnosine biosynthesis is dependent upon endogenous beta-alanine availability, by studying the effect of sustained dietary beta-alanine supplementation in the horse on the carnosine concentration in types I, IIA and IIB skeletal muscle fibres. The diets of 6 Thoroughbred horses were supplemented 3 times/day with beta-alanine (100 mg/kg bwt) and L-histidine (12.5 mg/kg bwt) for a period of 30 days. Percutaneous biopsies of the m. gluteus medius from a depth of 6 cm were taken on the days immediately before and after the supplementatio...
The effects of an endurance ride on metabolism and neutrophil function. The effects of an endurance ride on neutrophil functions in endurance-trained horses were evaluated and related to metabolic changes and changes in cortisol concentrations. Blood samples were taken from 7 horses (aged 9-15 years) one day before, and then 30-60 min, 1 day and 8 days after the ride. The race resulted in elevated serum cortisol levels (< 465 nmol/l) and an increased neutrophil:lymphocyte ratio. Immediately post race, the neutrophil ability to engulf yeast was increased. One day after the race, a decrease in leukotriene B4 production (approximately 40%) and in the respiratory b...
Equid herpesvirus-induced immunosuppression is associated with lymphoid cells and not soluble circulating factors. A paresis isolate of equid herpesvirus 1 (EHV1, Ab4/8) and a plaque-purified virus derived from it (EHV1, Ab4/13), induced long-term suppression of both mitogenic and antigen-specific lymphocyte proliferations in adult outbred ponies. Peripheral blood mononuclear cells (PBMC) taken from a pony after EHV1 infection suppressed the in vitro function of normal cells but serum did not. This showed that the observed immune suppression was associated with circulating PBMC and/or their products rather than circulating soluble factors such as antigen or immune complexes. The results suggested that prod...
Immunolocalization of a novel protein (P19) in the endometrium of fertile and subfertile mares. One of the major progesterone-dependent endometrial proteins in the mare is a novel 19 kDa lipocalin (P19). This protein is secreted by the endometrial glands and is readily detectable in uterine secretions during the luteal phase of the oestrous cycle and early pregnancy. The function of P19 is unknown, but since most lipocalins act as carriers of small hydrophobic molecules, it probably transports a maternal factor to the conceptus during pregnancy. In this study, a high titre antiserum raised against recombinant-derived P19 was used to detect by immunohistochemistry the protein in endometri...
Oxytocin and PGF2alpha release in mares resistant and susceptible to persistent mating-induced endometritis. Mares resistant (n=7) and susceptible (n=9) to persistent mating-induced endometritis were artificially inseminated (AI) during oestrus with chilled extended semen. Blood samples were collected from 30 min before AI, for 2 h after AI and again between 16 and 18 h after AI. Samples were assayed for oxytocin and the PGF2alpha metabolite 13,14-dihydro-15-keto PGF2alpha (PGFM). AI caused a significant increase in oxytocin concentrations in both the resistant and susceptible mares and there was no significant difference in oxytocin release between the two groups of mares. Mean PGFM concentrations w...
The role of seminal plasma in post-breeding uterine inflammation. The effect of seminal plasma on polymorphonuclear neutrophil (PMN) chemotaxis, PMN phagocytosis and complement-induced cytolysis was determined using blood plasma pooled from four horses and seminal plasma pooled from two stallions. To investigate chemotaxis, complement in blood plasma was activated with E. coli lipopolysaccharide in the presence of 0-50% seminal plasma diluted with a standardized volume of McCoy's medium and placed in a chemotactic chamber. Chemotaxis of blood derived equine PMNs toward the chemoattractants was determined after incubation at 37 degrees C for 45 min. To invest...
Replication ability in vitro and in vivo of equine infectious anemia virus avirulent Japanese strain. An attenuated equine infectious anemia virus (EIAV), V26, was previously prepared by 50 passages of the Japanese virulent strain V70 in primary horse macrophage culture. The horses inoculated with this V26 virus were shown to raise neutralizing antibodies against V70 without any viremia. Here, we investigated the in vitro and in vivo replication ability of V26. Comparison of the long-terminal repeat (LTR) sequences between V26 and V70 revealed a large insertion within the LTR U3 hypervariable region of V26. V26 with the mutation in the LTR showed much higher promoter activity in vitro than V70...
Effect of prophylactic administration of hyperimmune plasma to prevent Rhodococcus equi infection on foals from endemically affected farms. The effect on foals of prophylactic administration of hyperimmune plasma to prevent R. equi infection was investigated on three farms at which R. equi infection was endemic. Sixteen foals between 10 and 39 days of age were intravenously given 1-21 of hyperimmune plasma. ELISA antibody titres against R. equi were significantly increased and maintained at high levels for over 30 days in most of the recipient foals. The prevalence of R. equi infection was 6.3% (1/16) in the foals that received the immune plasma, and 26.3% (5/19) in the control foals not given the immune plasma on the three farms....