The immune system has adapted to effect different mechanisms to combat the multitude of potential pathogens in our environment. In particular, CD8 T cells are participants in the immune response to intracellular pathogens, which include viruses, certain types of bacteria, and protozoa. Classified as members of the adaptive immune system, antigen-specific CD8 T cells after activation eventually form a pool of memory. Memory cells have an enhanced ability to protect against subsequent infections. The generation of antigen-specific CD8 T cells, therefore, is a potential approach in the design of vaccines, especially for those pathogens in which the humoral response is insufficient to protect the host.