function of antibody?
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Antibodies are capable of having an impact on organisms in the absence of effector cells or effector molecules such as complement. For the most part, the impact of antibodies by themselves can be measured in vitro as neutralization of organism infectivity. Neutralization is herein referred to as the ability of antibody by itself to inhibit infection of susceptible cells or, in the case of some extracellular organisms, to inhibit an initial pathogenic step. Importantly, as described below, neutralization involves many potential mechanisms. Furthermore, it should be emphasized that other antibody functions in addition to neutralization may ultimately be involved in prevention or clearance of infection, even by antibodies that neutralize the relevant organism in vitro .
Neutralization of infectivity In vitro, antibodies are capable of blocking the infectivity or pathogenesis of viruses, bacteria, parasites, and fungi. Neutralization generally occurs as a result of interfering with an organism's attachment to host tissues. However, it is now clear that several mechanisms account for neutralization and that a single antibody or antibodies with different specificities can neutralize a given organism, at least in vitro, through multiple mechanisms.
Pre-attachment neutralization
Some antibodies have been shown to inhibit infectivity by binding to organisms and causing them to aggregate. Aggregation or agglutination by IgA may allow more efficient entrapment of bacteria in mucous and subsequent clearance by peristalsis (2,3). Although aggregation is more likely to occur with polymeric IgA and IgM, some neutralizing IgG antibodies can aggregate polio virus; the aggregation results in less infectivity, probably by reducing the number of encounters between virus and host cells (4,5).
Antibodies have also been shown to immobilize or “paralyze” organisms, such as the channel catfish pathogen Ichtyophthirius multifiliis . The IgA mAb Sal4 can render Salmonella enterica immobile, independently of agglutination, although Sal4 also specifically interferes with uptake into epithelial cells. Antibodies directed against Pseudomonas aeruginosa flagella inhibit motility of that organism . Polyclonal antibodies, induced by immunizing mice with Vibrio cholerae outer membrane vesicles, protect suckling mice from oral V. cholerae challenge, likely by inhibiting the motility of the organism . Antibody may slow the random movement of HIV-1 in vaginal mucous, presumably reducing the number of times the virus can make contact with the epithelial surface; this antibody function appears to rely in part on Fc interactions with components of the mucous.
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Neutralization of infectivity In vitro, antibodies are capable of blocking the infectivity or pathogenesis of viruses, bacteria, parasites, and fungi. Neutralization generally occurs as a result of interfering with an organism's attachment to host tissues. However, it is now clear that several mechanisms account for neutralization and that a single antibody or antibodies with different specificities can neutralize a given organism, at least in vitro, through multiple mechanisms.
Pre-attachment neutralization
Some antibodies have been shown to inhibit infectivity by binding to organisms and causing them to aggregate. Aggregation or agglutination by IgA may allow more efficient entrapment of bacteria in mucous and subsequent clearance by peristalsis (2,3). Although aggregation is more likely to occur with polymeric IgA and IgM, some neutralizing IgG antibodies can aggregate polio virus; the aggregation results in less infectivity, probably by reducing the number of encounters between virus and host cells (4,5).
Antibodies have also been shown to immobilize or “paralyze” organisms, such as the channel catfish pathogen Ichtyophthirius multifiliis . The IgA mAb Sal4 can render Salmonella enterica immobile, independently of agglutination, although Sal4 also specifically interferes with uptake into epithelial cells. Antibodies directed against Pseudomonas aeruginosa flagella inhibit motility of that organism . Polyclonal antibodies, induced by immunizing mice with Vibrio cholerae outer membrane vesicles, protect suckling mice from oral V. cholerae challenge, likely by inhibiting the motility of the organism . Antibody may slow the random movement of HIV-1 in vaginal mucous, presumably reducing the number of times the virus can make contact with the epithelial surface; this antibody function appears to rely in part on Fc interactions with components of the mucous.
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Antibodies are glycoproteins and are also called immunoglobulins. They are present in the blood and function together with the human immune system. They are used by the immune system to identify, attack and kill foreign objects such as bacteria and viruses. They can also be produced by medical science and used to boost the immunity of patients to prevent infection.
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