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Immunity can be acquired either actively or passively. Immunity is acquired actively when a person is exposed to foreign substances and the immune system responds. Passive immunity is when antibodies are transferred from one host to another. Both actively acquired and passively acquired immunity can be obtained by natural or artificial means.
He further formalised the theory in his 1959 book The Clonal Selection Theory of Acquired Immunity. He explained immunological memory as the cloning of two types of lymphocyte. One clone acts immediately to combat infection whilst the other is longer lasting, remaining in the immune system for a long time and causing immunity to that antigen.
Adaptive (or acquired) immunity creates an immunological memory leading to an enhanced response to subsequent encounters with that same pathogen. This process of acquired immunity is the basis of vaccination. Dysfunction of the immune system can cause autoimmune diseases, inflammatory diseases and cancer.
Immunity developed as an individual is exposed to antigens is called adaptive or acquired immunity, in contrast to immunity developed at birth, which is innate immunity. Acquired immunity depends upon the interaction between antigens and a group of proteins called antibodies produced by B cells of the blood. There are many antibodies and each ...
Passive immunity is the immunity acquired by the transfer of ready-made antibodies from one individual to another. Passive immunity can occur naturally, such as when maternal antibodies are transferred to the foetus through the placenta, and can also be induced artificially, when high levels of human (or horse ) antibodies specific for a ...
Innate immune memory (also called trained immunity) is neither antigen-specific nor dependent on gene rearrangement, but the different response is caused by changes in epigenetic programming and shifts in cellular metabolism. Innate immune memory was observed in invertebrates as well as in vertebrates. [3] [4]
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Ironically, Darwinian evolution may act on these neo-Lamarckian acquired characteristics as well as the cellular mechanisms producing them (e.g. methyltransferase genes). Epigenetic inheritance may confer a fitness benefit to organisms that deal with environmental changes at intermediate timescales. [67]