This is a variation of the "does the immune system run out of memory" question.
Here's a (possibly imperfect) thought experiment: You take two twins. One of them lives in a bubble from birth. One of them is Mike Rowe from Dirty Jobs, and gets exposed to all sorts of antigens as well as vaccines. When they are 30 years old, you expose both of them to an antigen that neither has seen before. What happens?
PS: Note that while this example is illustrative, my question is really about whether there is any way at all in which the response of a naive immune system to a novel antigen is different from that of a very educated immune system (which has also not seen the antigen before). For instance, would the same amount of antigen be required to stimulate the immune system? Would the antibody count several months or years post-exposure differ?