why are antigens so damn specific to antibodies & how?
142880
Antibodies are highly specific for one particular antigen, which is why the immune system (in theory) works so well. \n\nAn antibody kind of looks like a "Y". The base of the Y (the straight part) is a CONSTANT region, meaning that it is the same for every type of antibody, no matter what antigen the antibody recognizes. The constant region contains amino acid sequences necessary for the antibody to bind to other cells of the immune system, but not the antigen.\n\nThe top part of the "Y" is known as the VARIABLE region, and contains specific amino acid sequences that recognize a specific antigen. When the B cell that produces antibodies (plasma cell) is maturing in the lymph node's medullary cords, it undergoes what is called VDJ rearrangement, which means that the V, D, and J regions of the antibody protein are assembled in such a way as to make a unique antibody. There are several areas each of the V, D, and J gene, but only one is selected for each type.\n\nTherefore, a large amount of antibodies can be made that all have unique variable regions thanks to VDJ rearrangement. This means that one antibody can have one particular VDJ sequence, while another antibody has a different VDJ sequence. Therefore, these two antibodies can specifically recognize different antigens.
262510
Cells of the immune system more specifically B cells produce antibodies with shapes similar to the receptors on the foreign cells. Therefore these antibodies fit into the receptor sites on the membrane of the foreign cell and causes its membrane to break down.
1010410
protein molecules serve as antibodies to fight of any foreigners such as bacteria and viruses
776733
I assume the end of the question was "antibodies" or "antigens" and the answer is false for both.\n\nHowever there have been a few moderately successful attempts at engineering antibodies with catalytic activity. But in normal cellular physiology only specific enzymes speed up chemical reactions.
529232
There can be a 3 months window period, after this, if u have a negative result, so u are negative with Elisa. But if u are possitve with the Elisa, u have to make it with western blot. Some places take it to 1 month, the window period. 95% of the people seroconversion from 2 to 6 weeks. \n\nHope this can be usefull
675044
Normally, the body learns to defend itself through experience - by encountering, battling and remembering one enemy after another. For decades, medical science has taken advantage of this ability by using vaccination to create immunity - the immunologic "memory" of a disease. Allergic reactions occur after the immune system mistakenly learns to recognize innocent foreign substances (allergens) as potentially harmful.\n\nThe following story illustrates how an allergy can develop:\n\nOver a field of ragweed plants floats an invisible cloud of pollen grains, soon carried by the wind into a nearby town. The pollen is inhaled by a child whose body has never been exposed to this substance before.\n\nBecause of some genetic predisposing factor, this child's immune system overreacts and produces large numbers of IgE antibodies, all specially designed to respond to ragweed pollen. Several of the antibodies attach themselves to cells in the child's nasal passages and upper respiratory tract.\n\nThese cells (known as mast cells) contain strong chemicals called mediators, the best-known of which is histamine.\n\nLater, when the child inhales the same kind of pollen again, proteins from the pollen bind in a lock-and-key fashion to the specially designed antibodies on the surface of the mast cells. This sets off an explosion of sorts, as the mediators burst from inside the mast cells, destroying the pollen and also damaging surrounding tissues. The results are sneezing, a stuffy head, sniffling, stuffed-up head and red, watery eyes - well-known hallmarks of allergies.
115334
Generally polyclonal anitbodies are used to bind non-specifically to antigens. For instance, you might use monoclonal antibodies to specifically bind to your protein of intererst. You might then use polyclonal Ab to bind the rest of the proteins i.e. to block off the other available 'slots'
689200
It is not chemistry.  There is some unknown trigger that causes your body (B cells that have differentiated into plasma cells to be specific)to begin producing antibodies to your own proteins or DNA or RNA, etc.  These antibodies are called autoantibodies.
756226
The proteins shape determines its function.  Most proteins have to bind to something else in order to do its job.  If it's not a specif shape, it can't bind.
682548
oh my god - some of these answers are scary.\n\nthe question is very excellent though and very correct. the anti-A and anti-B CAN destroy the patients red cells if transfused to a group A or group B or group AB individual.\n\nhowever:\n\nthe antibodies are in the plasma and modern practices in blood processing split the components into their various parts - plasma and platelets and red cells. the red cells has very little plasma on them so very little anti-A or anti-B is transfused\n\ndonations with plasma on them are tested to see if the levels of anti A or anti B might be considered harmful and those donations with high titre (levels) of anti-A or anti-B are marked as not for transfusion to group A or B or AB patients.\n\nthe term universal donor is a very misleading one, in general it is true and group O can give to any other group, but precautions are necessary and are taken by transfusion services
177972
try these links. they are a quite a helpful read. \n\nwww.merck.com/mrkshared/ mmanual/section11/chapter143/143c.jsp\n\nwww.pnas.org/cgi/content/full/102/2/419\n\nwww.autoimmuneinc.com/R_and_D/tech.html\n\nwww.sciencemag.org/cgi/content/figsonly/309/5739/1380\n\ngood luck and have fun!!!
417322
Been a while since immunology, I'll try my best. There are two types of region on an antibody, a constant region and a variable region. The genes coding for the constant region or invariant but the genes coding for this variable region undergo a process known as somatic hypermutation. It is difficult to explain succinctly so know that the genes for the variable segment are arranged into what we call V, D, and J segment. There are multiple V, J, and D segments in the gene for the variable region and their different arrangements into a coding unit account for the majority of antibody diversity.
895535
Antigens were originally defined as non-self molecules which bound specifically to antibodies. In practice, the term antigen is used to mean any molecule recognized by the immune system. \n\nAntigens which induce adaptive immunity are called immunogens. All immunogens are antigens, and are usually called antigens unless their ability to induce an immune response is being discussed. Some antigens, called haptens, are not immunogenic unless they are covalently linked to immunogenic carriers (usually proteins). Haptens can bind antibodies once the antibodies are produced, but haptens will not induce antibody synthesis on their own. Small non-protein organic molecules, for example the antibiotic penicillin, are haptens.\n\nImmunogenicity is influenced by \n\nthe chemical nature of the antigen. \nthe antigen's size. \nthe antigen's usual presence in the body. \nantigen dose and route and timing of administration. \nwhether the antigen is easily phagocytosed. \nwhether antigen is efficiently presented to T cells on MHC. \nthe maturity of the immune system and specific lymphocytes. \nNote that immunogenicity depends on the immune system as well as on the antigen. \n\nImmunogenicity is generally higher for proteins than for other organic molecules. Protein antigens, which are the predominant sort that activate helper T cells, consequently induce more B cell antibody production, synthesis of IgG or IgA, and generation of memory B and T cells. T-independent antigens, which activate only B cells, induce IgM synthesis but not other adaptive immune responses.\n\nImmunogenicity increases with molecular size and complexity. Haptens are generally non-proteins or they are too small to be immunogenic unless they are covalently attached to a carrier protein molecule. Some carbohydrate antigens can stimulate B cells to secrete IgM in the absence of T cell help but do not elicit IgG or memory cells. Human infants make poor responses to carbohydrate antigens, so early vaccinations with bacterial polysaccharide antigens employ protein carriers. Aggregated proteins are easily phagocytosed and more immunogenic than soluble proteins. Adjuvants, including bacterial products, alum, or oil emulsification of antigen, attract and activate antigen-presenting cells (dendritic cells and macrophages) and slow antigen release to prolong exposure and improve immunogenicity.\n\nEach part of the antigen bound by a unique antibody is called an epitope. Most proteins have several epitopes that are recognized by different B cells and induce a polyclonal antibody response. In a polyclonal response, several clones of B cells each make different antibodies, all able to bind to the same antigen but at different epitopes. Epitopes may be shared by closely related antigens (cross-reactivity), so that antibody made to tetanus toxoid binds tetanus toxin. A protein epitope may be a linear sequence of amino acids or it may be assembled by protein folding. Epitopes with definite three-dimensional shapes and charged amino acids are particularly well recognized by antibodies. External membrane and cell wall molecules, often present in many copies on the pathogen, are common B cell antigens. A small peptide of 4-6 amino acids could fit into an antibody binding site, but larger proteins have more extended epitopes across their surfaces.\n\nActive immunity is induced by exposure to antigen. Antigen dose and the route and timing of antigen contact, as well as immunogenicity, influence the magnitude and nature of the immune response. Very high or very low doses of antigen induce tolerance, the inability to respond to that antigen, while intermediate doses induce immunity. We are generally tolerant to cell-bound and soluble antigens present in our own bodies. Oral tolerance to foods is common, although some foods induce allergic reactions. \n\nAntigens encountered in body tissues through subcutaneous or intramuscular injection are carried by lymph and macrophages into the lymph
708697
For any molecule to perform its function it must recognize other molecules in the cell that it will react with them. the only way the reactants can meet is through binding to each other through their shapes. for example, if antibodies do not have their specific structures that can recognize specific antigens there will be no immune system and no disease will be treated. Another example is enzymes, the special 3-D structures create unique site called active sites that fit only the substrate of that enzyme, so any subtle change in the active site will make the enzyme nonfunctional and no reaction will be carried out.
199115
on red blood cells there are two major antigens A and B among other minor antigens.these designate one's blood group.\nBlood group O is indicative of one having no blood group antigens on his/her red blood cells.\nfor any blood group antigen there's a corresponding blood group antibody in the blood fluid i.e plasma or serum.for example if you are blood group A then your blood will have antibody B,if you have blood group B then you have antibody A.however if one is blood group O then that means that you have both antibodies A and B,and if you are blood group AB then you have no major blood group antibodies i.e neither antibody A nor B is present in your plasma.now if a blood group A person receives any blood group other than A or O then the antibodies in the plasma cause clumping(coming together)of the foreign blood cells.this causes blocking of the blood vessels with disastrous results.please note that it's the foreign blood cells that are clumped by the native antibodies if they match i.e A with Antibody A,B with antibody B,O with either A or B and AB by none.for this reason O can donate blood to any blood group but cannot receive blood except from another O and AB can receive blood from anyone but cannot donate their blood to anyone except AB.there is another group of antigens known as the rhesus factors.one is either rhesus positive(+) or negative(-).therefore a blood group O+ can donate blood to any rhesus+ blood group and blood group AB+ can receive any rhesus+ blood group.hence to answer your question blood group O can take blood only from an O of the correct rhesus factor
313806
Affinity purification is a method commonly used in protein chemistry to isolate a product from a mixture that interacts with another known, and previously isolated, product.  Negative affinity purification, on the other hand, is a method used to deplete a known contaminant from a protein mixture based upon its ability to bind to a different molecule.\n\nFor example, a scientist wants to make an antibody specific for a novel protein. He/she produces the protein as a fusion product linked to GST (glutathione-S-transferase), since there are many methods to allow isolation of this fusion protein (by affinity purification techniques).  This fusion product is then injected into a mouse or rabbit and after some time the animal produces antibody in its blood.  \n\nWhile it might be acceptable to use the whole serum (containing the protein specific antibody) from this animal for subsequent experiments, the antibody of interest is only a small fraction of the total protein in the serum.  So, the scientist purifies the antibody directed against the protein of interest using a column containing the GST-fusion product used for inoculation (again, affinity purification) and elutes the antibody fraction that recognizes this protein.  Great, but the scientist knows that the GST component of the fusion protein will also induce the mouse to make antibodies, and that these GST-specific antibodies will be purified by the previous step.  So, he/she decides to do NEGATIVE Affinity Purification by passing the purified antibody mix over a column that contains the GST protein alone (not the fusion product) and then collects the antibody that DOES NOT bind to the GST alone.  Voila, protein specific antibody without contaminating GST-specific antibody... using negative affinity purification.
697002
It's used in serological testing.  The basic premise of serology the interaction of antibody and antigen.  When doing an experiment, like an ELISA or EIA,  you are looking for antibody/antigen binding.  You use a labeld antibody to visualize the reaction.\n\nOnce example would be if you had antibody attached to the well of a microplate, and you wanted to see if there was antibody in a person serum.  You would add the serum, wait a bit, then wash it off very well, so that the only antibody still left woud be attaced to the antigen.  Then you would add your labeled antibody, choosing one that binds to all human antibodes.  Wait, then wash, then add the last step to turn the label on. You could also start out with antibody in the wells, and be looking for antigen in the serum.  It's a bit tricky to explain, so I linked to some pictures of it.  It's the second to the last step that uses the labeled antibody.  \n\nThere are several different types of labels attached to antibodies.  Some change color, so emit a certain wavelenght of light, at one time, radioactive ones were popular, but those have gone the way of safer tests.