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Antibodies contribute to immunity in three ways: They prevent pathogens from entering or damaging cells by binding to them; they stimulate removal of pathogens by macrophages and other cells by coating the pathogen; and they trigger destruction of pathogens by stimulating other immune responses such as the complement pathway. [56]
Polyclonal antibodies are collection of antibodies that target the same pathogen but bind to different epitopes. Polyclonal antibodies are obtained from human donors or animals that have been exposed to the antigen. The antigen injected into the animal donors can be designed in such a way to preferably produce neutralizing antibodies. [25]
1) Antibodies (A) and pathogens (B) circular in the blood. 2) The antibodies bind to pathogens with complementary antigen sequences, engaging in opsonization (2a), neutralisation (2b), and agglutination (2c). 3) A phagocyte (C) approaches the pathogen, and Fc region (D) of the antibody binds to one of the Fc receptors (E) on the phagocyte.
The antigens and antibodies combine by a process called agglutination. It is the fundamental reaction in the body by which the body is protected from complex foreign molecules, such as pathogens and their chemical toxins. In the blood, the antigens are specifically and with high affinity bound by antibodies to form an antigen-antibody complex.
Here, a pathogen spends most of its life-cycle inside host cells, where it is shielded from direct contact with immune cells, antibodies and complement. Some examples of intracellular pathogens include viruses, the food poisoning bacterium Salmonella and the eukaryotic parasites that cause malaria ( Plasmodium spp. ) and leishmaniasis ...
Step 5: When the B cells are activated, some B cells turn into plasma cells and are released in the blood, while other B cells become B memory cells that quicken response for a second exposure. Step 6: Plasma cells then secrete antibodies, which bind to antigens to fight the invading pathogens.
The typical ADCC involves activation of NK cells by antibodies in a multi-tiered progression of immune control. [5] A NK cell expresses Fcγ receptors.These receptors recognize and bind to the reciprocal portion of an antibody, such as IgG, which binds to the surface of a pathogen-infected target cell.
Active immunity is acquired through the exposure to a pathogen, which triggers the production of antibodies by the immune system. [7] Passive immunity is acquired through the transfer of antibodies or activated T-cells derived from an immune host either artificially or through the placenta; it is short-lived, requiring booster doses for ...