257 Virgin Olive Oil Benefits Neutrophils: the first cells to arrive at an infection site. They secrete enzymes that help destroy invading microbes. Neutrophils are the primary component of pus and the most abundant white blood cell type during infections. Basophils: cells responsible for inflammatory processes. They contain small granules that release enzymes which trigger an inflammatory response when infection occurs. Allergies and asthma are caused by uncontrolled basophil activity in response to antigens that are not inherently harmful to the body, leading to inflammatory reactions that may become severe. Eosinophils: cells specialised in responding to parasitic infections, including protozoa (e.g., amoebas, giardia, Plasmodium -the malaria parasite-), worms (e.g., anisakis larvae, roundworms, tapeworms), and ectoparasites (e.g., ticks, fleas, lice, mites). Monocytes and macrophages: the largest type of leukocytes. Monocytes form in the bone marrow and circulate in the blood, migrating to tissues where they differentiate into macrophages. Macrophages destroy microbes, ingest foreign material, remove dead cells, and stimulate immune responses. They present antigens on their surface for recognition by lymphocytes, which then initiate a specific immune response. For this reason, they are called antigen-presenting cells. Dendritic cells and natural killer cells are also part of the immune system. Dendritic cells are found in the blood, skin, and other tissues. They present antigens to T cells, stimulating an immune response. Like macrophages, they can ingest pathogens. Natural killer cells act similarly to CD8+ T cells, destroying cells that pose a threat. Disorders of the immune system can lead to various diseases. Some conditions (e.g., AIDS) or factors (e.g., ageing) can impair the immune system, causing immunodeficiency and increased susceptibility to infections and cancer. In contrast, autoimmune diseases result from an overactive immune system attacking normal tissues as if they were foreign organisms. Humans have two main types of immunity. Innate (non-specific) immunity is present from birth, remains constant over time, and provides a general defence without memory. Adaptive (specific) immunity develops throughout life in response to exposure to pathogens and retains memory for future protection. Both types of immunity act in a coordinated and integrated manner to defend the body against invading agents. Some authors recognise a third type of immunity, referred to as passive immunity. This term refers to the protection provided by an external source, such as the antibodies passed from the mother to the newborn through breast milk. It provides temporary immunity against the diseases to which the mother has previously been exposed. - innate or non-specific immunity Innate immunity is also called natural or non-specific immunity. It is present from birth (congenital), inherited, and remains active throughout life. It does not require prior exposure to a pathogen to function, meaning it lacks the memory characteristic of adaptive immunity. It provides an immediate response to invading agents. The cells of this immune system surround and isolate the pathogens so that they can later be destroyed within the immune cells. In addition to immune cells, this type of immunity includes physical barriers that prevent the entry of pathogens, such as the skin or stomach acid. - adaptive or specific immunity Develops throughout a person’s life and is acquired progressively through exposure to pathogens. It has more effective and complex mechanisms, provides a longer-lasting response, and retains memory of the invading microorganism’s characteristics,
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