Do antibiotics attenuate immune response on subsequent exposure to same bacteria?
A quick search on ISI Web of Knowledge yielded this paper:


  R J North, P A Berche and M F Newborg (1981) Immunologic consequences of antibiotic-induced abridgement of bacterial infection: effect on generation and loss of protective T cells and level of immunologic memory. Journal of Immunology 127: 342-346


The authors investigated the effects of ampicillin treatement in mice infected with Listeria monocytogenes. They reported an abridgement of T cell-mediated antibacterial immunity and in particular an effect upon the development of memory:


  Moreover, Ampicillin-induced abridgement of infection, either before or at the time of peak primary response, resulted in the expression of greatly reduced levels of immunologic memory at a later time. This indicates that memory cells are generated throughout the entire course of the primary anti-Listeria response, including the period of its decay.


Presumably any treatment that reduces the need for an immune response will have an effect upon the production of useful memory T cells.