CD8A and bacterial infectious disease: To our knowledge, our study is the first to clearly demonstrate effector imprinting by IL-12 in CD8+ effector memory T cells formed in response to microbial infection, an effect that may have been masked in viral and bacterial infection systems, due to the production of multiple and redundant “signal 3” cytokines and to the common practice of using peptide-pulsed rather than naturally-infected antigen presenting cells for restimulation.