The numbers of antigen-specific MHC class I restricted effector CD8+ T cells induced in mice spleens 9 days after primary infection and 5 days after challenge with the wild type Lm (2×103) was determined through evaluation of the number of IFN-γ producing CD8+ T cells induced showing reactivity against the dominant H-2Kd restricted LLO91–99 epitope [25] in an in vitro ELISPOT assay. Here, CD8A is linked to infection.