Parasites immunity

Basophils are the least numerous and least well characterized of the circulating leukocytes. While they are not derived from the same progenitor cell as tissue mast cells, basophils and mast cells have several similar functions, including their participation in hypersensitivity reactions. Basophils have also been attributed roles in plasma lipolysis, parasite immunity, tumor cell cytotoxicity, and hemostasis. Increases have been associated with persistent lipemia, parasitism, allergic diseases, certain neoplastic diseases, and administration of certain drugs (e.g., heparin, penicillin). 

T-Lymphocytes (4,5) and other cellular components of the immune system also have equally wide implications in regulation of the normal immune system. The T-lymphocytes play a central role in the body s response to harmful antigens and tumor—host interaction (4). Responses involve antigens derived from vimses, bacteria, parasites, and tumors. T-ceUs also participate in the immune surveillance response, where self-antigens are recognized, but usually sequestered within the cell and, when exposed, become markers of cellular damage. 

The immune system in vertebrates provides a defense mechanism against foreign parasites such as viruses and bacteria. Three main properties are essential to its successful operation specific recognition of foreign molecules, the ability to destroy the foreign parasite, and a memory mechanism that allows a more rapid response to a second infection by the same microorganism. 

The action should not disturb the immune system, such as cell defence action known as phagocytosis and the production of antibody, which take place naturally in the presence of parasites. 

IFNs are natural glycoproteins produced by the cells of most vertebrates in response to the challenge by foreign agents, such as infectious organisms (viruses, bacteria, fungi, and parasites), and by tumor cells. IFNs can be produced by cells of the innate and adaptive immune systems and by non-immune cells such as fibroblasts and epithelial cells. 

The science of immunology not only encompasses the body s immune responses to bacteria and viruses but is extensively involved in tumour recognition and subsequent rejection the rejection of transplanted organs and tissues the elimination of parasites ftom the body allergies and autoimmunity (the condition when the body mounts a reachon agairrst its own tissues). 

Although acquired immunity to some parasitic diseases may lower the level of infection, absolute immunity as seen in bacterial and viral infections is seldom seen in parasitic diseases. Since parasitic infections produce a wide variety of antigens because of the many life cycle phases, it is more difficult to identify a constant antigenic protein against which specific antibodies are protective. However, malaria remains a likely candidate for a vaccine and there are ongoing studies to develop one. 

The drawback with late lambing is its dependence either on a buoyant store lamb market in September and October or else on the feasibility of growing a catch crop, such as stubble turnips or rape, on the farm, so that lambs can be fattened satisfactorily outdoors during the autumn and early winter. Again, intestinal parasites can be a problem, with the period of maximum risk, late July and August, occurring before the younger lambs have had a chance to build up their own immunity. 

Herve, M., et al. (2003). Pivotal roles of the parasite PGD2 synthase and of the host D prostanoid receptor 1 in schistosome immune evasion. Eur. J. Immunol 33, 2764-72. 

For much of its life cycle a parasite s environment is its host. A principal, and potentially lethal, feature of this environment is the host immune response. Diversity in parasites interactions with this aspect of their environment may therefore be expected. The host immune response varies between different hosts and so, if this is considered as a selection pressure, it may produce the ideal conditions for the generation of diversity in immune-mediated parasite-host interactions. 

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