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Antibodies

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Antibodies

Postby biology_06er » Sun Jun 10, 2007 6:52 am

Hi there..

Just wondering when it says that antibodies help destry pathogens etc this can only happen if the body has been exposed to this same pathogen before right?...so say for example "strain A" enters my body, the immune response takes place with the final result being plasma/memory cells being produced...these plasma cells secrete the antibodies that will forever be in my system right? and the memory cells are incase "strain A" ever comes back into my body can help destroy this strain along with the antibodies right?...so once these antibodies hv been secreted via plasma cells does this mean that they destroy the rest of Strain A within me

if this is the case i just read that there are 3 main ways of destryong antigens...like neutralizaion, opsonization and complement...does this mean that in order for the antibodies to bind to these forign objects my system shld hv come across these bugs before???

one last thing...when a pathogen enters us are cells such as macrophages the 'first line of defense' ie meaning that antibodies will not be secreted due to the fact these macrophages/neutrophils can destroy it

can someone please help, i have an exam on friday and wanna make sure i have these concepts correct

cheers,
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Postby MrMistery » Sun Jun 10, 2007 11:32 am

well, phagocytes are the first line of defense because they operate quickly. It takes time to make antibodies.
Opsonisation, precipitation, complement activation and neutralisation is HOW the antibody distroys the antigen. If the antibody simply binds to the antigen that usually does not inactivate the pathogen ;)
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Postby Darby » Sun Jun 10, 2007 5:48 pm

For most diseases (ones that you survive), you have a lot of quick responses that fight it off (although it often doesn't feel that quick); unless the organisms can evade those general defenses, they don't last long enough to deal with antibodies, which usually react to later exposures.
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Postby biology_06er » Sun Jun 10, 2007 9:17 pm

Hi there...

but if antibodies are how how pathogens are removed via those pathways, neutralization the antibodies have to be produced first right via the humoral response..so say we have a bug enter us...antibodies are made and its these antibodies that bind to the bug and eliminated it right via the pathways??

is this correct

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Postby blcr11 » Mon Jun 11, 2007 4:51 pm

There are two broad categories of immune response: an antibody or serological response, and a cellular response. Different antigens can ellicit one or the other or even both types of response depending on the antigen and how it is presented to the immune system. An antigen is quite literally anything that can stimulate some kind of immune response. Most natural antigens are parts of proteins or complex carbohydrates and are borne by cells of all sorts, including your own, mine, everyone else’s, bacteria, parasites…and so on.

When a bacterium invades a naïve system (one that has not seen the bug before), usually there are enough B-cells already present that express antibody with at least some affinity for antigens present on the pathogen. (If it has been seen before, the response can come more quickly, but it won’t necessarily be a different response.) So some serological response is usually possible from the beginning. The B-cells can secrete antibodies that “neutralize” an infectious agent, most likely by interfering with a cell-pathogen interaction required for infection; or antibodies that cause agglutination or clumping into large aggregates which will be cleared by the kidneys (though, too much of this can damage the glomeruli); or that attract macrophages by way of the Fc ends and Fc-receptors on the macrophage, which then can either engorge the pathogen, if it is small enough, or release lytic enzymes that will damage the invader, and or release cytokines that act to call in other lytic cells; or, finally, antigen-antibody complexes can activate complement, which is similar to the macrophage response in that it involves the activation and release of lytic enzymes that are intended to damage the pathogen and restrict its ability to infect.

If the initial response is enough to get rid of the pathogen, then, aside from the production of some memory cells, that’s it; nothing else is needed. There are additional things that can happen if the infection isn’t removed by the simple serological response—like try to make antibodies with greater affinity toward antigens by undergoing further rounds of vdj recombination. Or the response could shift from primarily a serological response to a cellular one moderated by T-cells and company
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