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In Poland, Hemorrhagic Enteritis Virus (HEV) was first isolated in 1987. Over nearly thirty years numerous studies concerning the pathology of HEV infection of turkeys were conducted at the Department of Poultry Diseases in Olsztyn. The results of these studies contributed to one postdoctoral dissertation, five doctoral dissertations and one master’s thesis, as well as numerous publications and papers presented at national and international conferences. Over time, through the use of state of art laboratory techniques, such as flow cytometry and molecular biology, it has been demonstrated that Polish isolates of HEV are low pathogenic, but they possess strong immunosuppressive activity; moreover, these viruses occur very frequently in turkey flocks and are involved in pathological conditions of turkeys in our country. It has been further demonstrated that even the HEV isolates which are low pathogenic cause a subclinical course of the disease which impairs both humoral and cell mediated immune mechanisms, leading to exacerbation of ongoing disease processes and decreased vaccine induced immunity development, which consequently cause large economic losses in the turkey industry.
Genetic manipulation conducted for many years has resulted in breeding turkeys with very intensive growth rate and high percentage of muscle tissue. These features promote dysfunctions in the cardiovascular system. The aim of this article was to present current data on the etiology of cardiovascular system diseases in turkeys. In this paper the most recent data on dilated cardiomyopathy (round heart disease), spontaneous aortic rupture and perirenal hemorrhage syndrome are described.
In terms of its anatomy and functions, the reproductive system of birds is significantly different from the one found in mammals. It consists of only the left ovary and the left oviduct, which is constantly exposed to ascending infections because of its connection with the cloaca. Hence, the proper functioning of humoral and cell-mediated local immune mechanisms in this system is very important for maintaining its physiological functions. The expression of Toll-like receptors and the presence of T and B lymphocytes have been demonstrated in both the ovary and the oviduct of chickens. CD4⁺ T cell subpopulation is distributed mainly in the lamina propria of the oviduct, whereas in the submucous membrane and muscular layer these cells are found less frequently. CD8⁺ T lymphocytes are equally distributed in all abovementioned layers of the oviduct wall. IgY⁺ B cells are distributed among the epithelial cells, and they are closely connected with the glandular tissue of the oviduct, mainly in the infundibulum, magnum, and uterus regions. IgA⁺ and IgM⁺ B cells are present in the entire oviduct, but mainly in the glandular tissue of the magnum. IgY⁺ B cells have not been detected in the ovary, unlike IgM⁺ B cells, which have been demonstrated in the ovary stroma. In addition to T and B cells, antigen-presenting cells are present in the follicle wall and in the oviduct. During the early stages of reproductive maturation, a decrease in the number of immunocompetent cells is observed in the reproductive system, and the local immnosuppression increases the susceptibility of birds to Salmonella Enteritidis infections. The number of T and B lymphocytes in the mucous membrane of the oviduct decreases with age, which facilitates infections of the reproductive system. Additionally, the local immune mechanisms of the reproductive system in birds involve the transfer of protective IgY, IgA and IgM maternal antibodies to hatching eggs. The local immune mechanisms of the reproductive tract are responsible for preventing infections that disturb the physiological functions of the reproductive system and for protecting eggs from contamination.
This review article presents fundamental mechanisms of the local mucosal immunity in selected regions of the respiratory tract in healthy birds and in some pathological conditions. The respiratory system, whose mucosa come into direct contact with microorganisms contaminating inhaled air, has some associated structures, such as Harderian gland (HG), conjunctive-associated lymphoid tissue (CALT) and paranasal glands (PG), whose participation in local mechanisms of the mucosal immunity has been corroborated by numerous scientific studies. The nasal mucosa, with structured clusters of lymphoid tissue (NALT – nasal-associated lymphoid tissue) is the first to come into contact with microorganisms which contaminate inhaled air. Lymphoid nodules, made up of B cells with frequently developed germinal centres (GC), surrounded by a coat of CD4+ cells, are the major NALT structures in chickens, whereas CD8+ cells are situated in the epithelium and in the lamina propria of the nasal cavity mucosa. Studies into respiratory system infections (e.g. Mycoplasma gallisepticum) have shown the reactivity of the tracheal mucosa to infection, despite a lack of essential lymphoid tissue. Bronchus-associated lymphoid tissue (BALT) takes part in bronchial immune processes and its structure, topography and ability to perform defensive function in birds is largely age-dependent. Mature BALT is covered by a delicate layer of epithelial cells, called follicle-associated epithelium (FAE). Germinal centres (GC), surrounded by CD4+ cells are developed in most mature BALT nodules, while CD8+ lymphocytes are dispersed among lymphoid nodules and in the epithelium, and they are rarely present in GC. Macrophages make up the first line of defence mechanisms through which the host rapidly responds to microorganisms and their products in the respiratory mucosal system. Another very important element are polymorphonuclear cells, with heterophils being the most important of them. Phagocytic cells obtained from lung lavages in birds are referred to as FARM (free avian respiratory macrophages). Their number in chickens and turkeys is estimated to be 20 times lower than that in mice and rats, which indicates a deficit in the first-line of defence in the birds’ respiratory system. There are numerous B cells and antibody secreting cells (ASC) present throughout the respiratory system in birds. Their role comes down to perform antigen-specific protection by producing antibodies (IgM, IgY or IgA class) as a result of contact with pathogenic factors.
The aim of the research was to determine the efficiency of in ovo immunisation of turkeys against the haemorrhagic enteritis virus, while simultaneously applying a synthetic immunomodulator - methisoprinol - by the same route of administration. Dindoral SPF vaccine, in a dose of 0.1 ml of the solution prepared ex tempore after dissolving the vaccine in 100 ml of water for injection, and methisoprinol in a dose of 5 mg per egg, were administered in ovo on the 26th d of incubation. The control groups consisted of turkeys hatched from eggs into which only the methisoprinol or the vaccine was administered, as well as birds hatched from eggs that were not interfered with. The susceptibility of turkeys to HE virus infection was determined on the basis of the presence of HE antibodies in serum, the evaluation of a splenic index, and attempts to register the virus presence in the spleen 120 h after the control infections. The research proved the effectiveness of immunising turkeys against the haemorrhagic enteritis virus by administering Dindoral SPF vaccine in ovo. It was also demonstrated that the simultaneous application of methisoprinol, showing an antiviral effect, and the vaccine inhibited the development of post vaccinal immunity against this virus.
The aim of the research was to determine the influence of a synthetic immunomodulator methisoprinol applied in ovo as a 10% solution in doses of 5 mg per egg (group I) and 20 mg of active substance per egg (group II) on the 26th day of incubation on T-lymphocyte subpopulations in the blood and spleen of 5-day-old turkeys hatched from the treated eggs. The control group (group III) were turkeys hatched from eggs in standard hatchery conditions (without in ovo injections). The percentage of T-lymphocyte subpopulations was determined by flow cytometry using specific monoclonal anti-T CD3⁺, CD4⁺ and CD8⁺antibodies and an EPICS XL apparatus. It was demonstrated that methisoprinol applied in ovo in doses of 5 mg per egg stimulated non-specific mechanisms of humoral immunity in 5-day-old turkey poults hatched from the treated eggs, which resulted in a higher percentage of CD3⁺ and CD4⁺ T-lymphocytes in their blood and spleen. Methisoprinol applied in ovo in doses of 20 mg per egg stimulated mainly non-specific mechanisms of cellular immunity in 5-day-old turkey poults hatched from the treated eggs, as evidenced by a higher percentage of CD8⁺ T-lymphocytes in the spleen.
This review article presents immunological issues in the course of the turkey rhinotracheitis (TRT) emphasizing local immunity mechanisms, both humoral and cell-mediated, in the upper respiratory system. Studies on the influence of the humoral immunity in the course of infection and vaccinations against TRT have revealed many times the absence of correlation between the titre of specific IgY anti-aMPV (avian Metapneumovirus) antibodies in the serum and in the upper respiratory washings and the immunity against the occurrence of the clinical form of the TRT. Considering the above, T cells are increasingly often regarded as the main factor involved in the upper respiratory immunity against the TRT. However, there have been just a few reports on the role of the T cells in the local immunity processes in the infection with aMPV in turkeys. Additionally, studies of the T-cell-associated immunity against the TRT have given ambiguous results. Immunoprophylaxis issues against the aMPV infections are a significant part of the work where the authors confront current vaccination programmes against the perspectives of use of the future vaccines against the TRT. Future vaccines should face the following criteria: absence of the risk of immunosuppressive effect and reversion of vaccine strains virulence, ease-of-use combined with the possibility of administration of the vaccine to the large numbers of turkeys. The leading role in future vaccination programs for birds against the TRT is likely to be played by the in ovo technique and the recombinant vaccines. Great hopes are also linked with the development of subunit vaccines against the aMPV.
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