Epitopes and antigen-receptor formation

[Jedi of Zen]

This is actually a question from my microbiology class, but I thought this might be the more appropriate board -

What is the difference between an epitope and an antigen? Would I be correct in assuming that an epitope is a small, more specific portion of the (larger sized) antigen?

Also, where do antigen receptors and antibodies actually come from? I'm referring specifically to helper T-cells, which have antigen receptors. Thanks!

[canalon]

1) right. AN antigen can have many epitopes. The pitope is actually the part of the molecule recognized by the Antibody.

2) You can start by reading that http://www.biology-online.org/tutorials/1_cell_biology.htm
and if you do not find a satisfying answer rush to your library to find a good textbook of immunology.

[Jedi of Zen]

Thanks for your response.

I did indeed do some reading on the link you mentioned.

I'm also wondering - how do epitopes compare to idiotypes? Do the 2 fit together (ie, in terms of the "lock and key" concept behind the antigen-antibody complex)?

Thanks again.