| antigenic shift | Mutation, i.e., sudden change in molecular structure of RNA/DNA in microorganisms, especially viruses, which produces new strains of the microorganism; hosts previously exposed to other strains have little or no acquired immunity to the new strain; antigenic shift is believed to be the explanation for the occurrence of strains of microorganisms, such as the influenza virus, associated with large scale epidemics. (05 Mar 2000) |
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| antigenic switching | <immunology> The process by which a pathogenic microbe's genetic structure is altered tochange its surface antigens inorder to avoid being detected by the host's immune system. (09 Oct 1997) |
| antigenic variation | The phenomenon of changes in surface antigens in parasitic populations of Trypanosoma and Plasmodium (and some other parasitic protozoa) in order to escape immunological defense mechanisms. at least 100 different surface proteins have been found to appear and disappear during antigenic variation in a clone of trypanosomes. Each antigen is encoded in a separate gene. Antigenic variation is also known to occur in free living Protozoa and certain bacteria. (18 Nov 1997) |
| idiotypic antigenic determinant | The antigenic specificites defined by the unique sequences (idiotopes) of the antigen combining site. Thus anti-idiotype antibodies combine with those specific sequences, may block immunological reactions and may resemble the epitope to which the first antibody reacts. (18 Nov 1997) |