Covering a pathogen's antigen in antibodies make the pathogen less infectious and less pathogenic. In the image on the right, virus entry to the cell is prevented by<unk> es binding to the virus. In order to enter cells, pathogens such as circulating virus particles or extracellular bacteria use molecules on their surfaces to interact with the cell surface receptors of their target cell which allows them to enter the cell and start their replication cycle.<unk> es can inhibit the infectivity by binding to the pathogen and block the molecules needed for cell entry. This can be due to the antibodies statically interfering with the pathogens or toxins attaching to host cell receptors. In case of a virus infection,<unk> bs can bind to glycoproteins of enveloped viruses or capsid proteins of non-enveloped viruses. Furthermore,<unk> es can act by preventing particles from undergoing structural changes often needed for successful cell entry. For example,<unk> es can prevent conformational changes of viral proteins that mediate the membrane fusion needed for entry into the host cell. In some cases, the virus is unable to infect even after the antibody dissociates. The pathogen-antibody complex is eventually taken up and degraded by macrophages.<unk> es are also important in<unk>  the toxic effects of bacterial toxins. An example of a<unk>  is diphtheria antitoxin, which can neutralize the biological effects of diphtheria toxin.<unk> es are not effective against extracellular bacteria, as the binding of antibodies does not prevent bacteria from replicating. Here, the immune system uses other functions of antibodies, like opsonisation and complement activation, to kill the bacteria. Difference between<unk> es and binding antibodies Not all antibodies that bind a pathogenic particle are<unk> . Non-neutralizing antibodies, or binding antibodies, bind specifically to the pathogen, but do not interfere with their infectivity. That might be because they do not bind to the right region. Non-neutralizing antibodies can be important to flag the particle for immune cells, signaling that it has been targeted, after which the particle is processed and consequently destroyed by recruited immune cells.<unk> es on the other hand can neutralize the biological effects of the antigen without a need for immune cells. In some cases, non-neutralizing antibodies or insufficient amounts of<unk> es binding to virus particles can be utilized by some virus species to facilitate uptake into their host cells. This mechanism is known as antibody-dependent enhancement. It has been observed for Dengue virus and Zika virus.
Neutralizing antibody
Microantibody
Donor-specific antibody
Heterophile antibody
Blocking antibody
Isoantibodies
Panel-reactive antibody
Antibody