What is a protective epitope? An epitope is basically a part of antigen. So does it mean that when the epitope combines with an antibody, it helps in the functioning of the antibody instead of going against it?
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Lets define the nomenclature first: An antigen is a large structure (protein, virus, bacteria and so an) which is recognized by the immune system as foreign. The word antigen derives from the abbreviation ANTIbody GENerator. Exposure of our immune system to an antigen results in an immune response and the generation of many antibodies.
An epitope is a small part of an antigen - typically these are small structural elements or small peptides (8-11 amino acids in length) which are recognized by the binding site of an antibody. See the picture below (from here):
Here the antigen is the albumin protein. On the surface you can see 8 different epitopes which lead to the generation of 8 highly specific antibodies against the epitopes (antikörper is the german word for antibody). Every antibodies is highly specific for its epitope and will recognize no other epitope and helps raising an immune response against it. What happens after an antibody bound to its epitope can be read here.
Antibodies directed against a protective epitope are directed against (highly) conserved structures of the antigen. For example the recognize a highly conserved structure of a virus which means that even when this virus mutates (like influenza does) it will still recognize the conserved epitope and give protection against this virus (or better: antigen).
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$\begingroup$ understood. But what does a protective epitope mean? $\endgroup$– girl101Aug 21, 2014 at 11:07
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$\begingroup$ Ah, sorry, forgot to answer that. I will updated the answer, better now? $\endgroup$– Chris ♦Aug 21, 2014 at 11:40
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$\begingroup$ what is a protective epitope? I still dont find the answer of y question. what exactly is a protective epitope? $\endgroup$– girl101Aug 21, 2014 at 13:12
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1$\begingroup$ It is a normal epitope. But one which is widely distributed between different strains of a virus/bacteria etc. and gives you a very good protection against these antigens. $\endgroup$– Chris ♦Aug 21, 2014 at 15:44
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1$\begingroup$ The word protective is an adjective which describes the function of the noun epitope. It is an effective protector against infection. Like @Chris said its protectiveness is derived from recognizing a conserved region of a molecule. Recognizing a conserved region of a molecule is what merits the special adjective 'protective'. $\endgroup$ Aug 22, 2014 at 1:29