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The ability of the immune system to respond to pathogens is diminished in both the young and the elderly, with immune responses beginning to decline at around 50 years of age due to immunosenescence. [ 112 ] [ 113 ] In developed countries , obesity , alcoholism , and drug use are common causes of poor immune function, while malnutrition is the ...
An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellular bacteria, protozoa, helminths, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.
The mechanisms of absence of immune response may vary and involve complex immunological interactions, but can include absent or insufficient co-stimulatory signals from antigen-presenting cells. Haptens have been used to study allergic contact dermatitis (ACD) and the mechanisms of inflammatory bowel disease (IBD) to induce autoimmune-like ...
In immunology, clonal selection theory explains the functions of cells of the immune system (lymphocytes) in response to specific antigens invading the body. The concept was introduced by Australian doctor Frank Macfarlane Burnet in 1957, in an attempt to explain the great diversity of antibodies formed during initiation of the immune response.
Cellular immunity, also known as cell-mediated immunity, is an immune response that does not rely on the production of antibodies. Rather, cell-mediated immunity is the activation of phagocytes , antigen-specific cytotoxic T-lymphocytes , and the release of various cytokines in response to an antigen .
Normally antibodies can detect and differentiate molecules from outside of the body and those produced inside the body as a result of cellular activities. Self molecules as ignored by the immune system. However, in certain conditions, the antibodies recognise self molecules as antigens and triggers unexpected immune responses.
The history of phagocytosis represents the scientific establishment of immunology as the process is the first immune response mechanism discovered and understood as such. [1] [2] The earliest definitive account of cell eating was given by Swiss scientist Albert von Kölliker in 1849. [3]
The immune system may respond in multiple ways to an antigen; a key feature of this response is the production of antibodies by B cells (or B lymphocytes) involving an arm of the immune system known as humoral immunity. The antibodies are soluble and do not require direct cell-to-cell contact between the pathogen and the B-cell to function.