Another means of regulation that has been proposed is the idiotypic network hypothesis

Another means of regulation that has been proposed is the idiotypic network hypothesis

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Another means of regulation that has been proposed is the idiotypic network hypothesis. This theory suggests that the idiotypic determinants of antibody molecules are so unique that they appear foreign to the immune system and are, therefore, antigenic. Thus, production of antibody in response to antigen leads to the production of anti-antibody in response, and anti- anti-antibody and so on. Eventually, however, the level of [anti] n -antibody is not sufficient to induce another round and the cascade ends. CROSSREACTIVITY Crossreactivity can occur when two (or more) antigens share similar structural features. Consider three different antigens, as shown on the right. Antibody produced in response to Ag1 is very specific and would, therefore, have a large affinity constant (K) when combining with Ag1. However, Ag2 is similar in shape to Ag1 and is capable of interacting with anti-Ag1 antibody via two of three sites. The interaction between Ab and Ag2 is not as strong as the interaction between Ab and Ag 1 (i.e. K is much smaller)
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Unformatted text preview: but is still strong enough to allow binding. Hence, Ag1 and Ag2 are said to cross-react . Ag3, in contrast, cannot interact very well with anti-Ag1 antibody and would have a K value so low that significant binding would not occur. Ag3, therefore, would not cross-react with Ag1. Would antibody produced in response to Ag2 bind Ag3? Would antibody produced in response to Ag2 bind Ag1? Crossreactivity also forms the basis for several diagnostic tests. For example, infection with Treponema pallidum (syphilis) causes the production of antibodies that cross-react with a substance found in cardiac muscle, cardiolipin. Since it is much easier to obtain pure cardiolipin than pure Treponemal antigens, this cross-reaction is used to test for syphilis (Wassermann test). Likewise, antibodies produced against certain Rickettsia cross-react with antigens from Proteus . Since the latter are much easier to obtain, they can be used to test for the former....
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This note was uploaded on 11/05/2011 for the course BIOLOGY MCB2010 taught by Professor Jessicadigirolamo during the Fall '10 term at Broward College.

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Another means of regulation that has been proposed is the idiotypic network hypothesis

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