258 OLIVE OILS AND HEALTH allowing for a quicker recognition upon re-exposure. This immunity involves B lymphocytes, which produce antibodies, and T lymphocytes. Antibodies take time to develop, but after initial exposure, the immune system usually recognises the pathogen and responds more rapidly thanks to memory. Vaccines are based on this principle. They are biological medicines made from microorganisms (bacteria or viruses), dead or live but attenuated so they are harmless. They can also be created using fragments of pathogens, which do not cause disease, or specific components such as proteins or genetic material (RNA), as in some CoViD-19 vaccines. This sensitises the immune system to produce B and T lymphocytes that will protect against future attacks by the same disease-causing agent. - phagocytic activity Phagocytic activity (phagocytosis) refers to the action carried out by certain types of leukocytes (monocytes, macrophages, neutrophils) and dendritic cells, which surround and destroy microorganisms, ingest foreign materials, and eliminate dead cells. (See all these components in the introduction to this topic.) - immunoglobulin A Immunoglobulin A (IgA) is mainly found, and in large quantities, in mucosal secretions of the body: tears, saliva, colostrum, and breast milk. It is also present in the mucosa of the gastrointestinal, urogenital, and respiratory tracts, protecting these systems against infections. For this reason, it is considered to be the first line of defence, as mucosal surfaces are the most common entry points for pathogens. It acts as a barrier to prevent infectious agents from settling in the tissues and penetrating the bloodstream. This immunoglobulin is resistant to destructive enzymes in secretions and can also withstand the acidity of the intestine. It is also found in the blood and can be measured through laboratory tests. IgA works by preventing pathogens from attaching to cells, binding to them to form stable complexes. Additionally, it marks these pathogens and makes them visible to facilitate the action of immune system cells. Pathological increases in IgA occur in infections of the mucosa such as respiratory or intestinal infections. Selective IgA deficiency refers to the total or partial absence of this immunoglobulin. It is usually hereditary, although there are rare cases related to medication use. When there is an IgA deficiency, the body tries to compensate by increasing the production of other immunoglobulins (IgM and IgG). As a result, symptoms generally do not appear unless the deficiency is very severe. - interleukin-1 beta Is a protein produced by leukocytes and other cells in the body. This interleukin is an important mediator of the inflammatory response. It is also involved in multiple immune functions and various cellular activities, including cell proliferation, differentiation, and apoptosis. - Interleukin-6 Interleukin-6 (IL-6) is a cytokine produced by various types of cells involved in immunity (leukocytes, T lymphocytes, macrophages), as well as other cells like endothelial cells and fibroblasts. IL-6 acts on a wide range of cells and tissues and may promote or inhibit the growth of certain cells. It has a dual and sometimes opposing role in inflammation, being primarily pro-inflammatory but also having anti-inflammatory effects. Its measurement can be useful to assess immune system activation, as IL-6 levels increase in infections, sepsis, autoimmune diseases, cardiovascular disease, and some cancers. It is also considered a potential inflammatory marker for severe CoViD-19 infection.
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