Attrition of T cell memory: Selective loss of LCMV epitope-specific memoryCD8 T cells following infections with heterologous viruses

Using a variety of techniques, including limiting dilution assays (LDA), in tracellular IFN gamma assays, and D-b-IgG1 MHC dimer staining to measure vi ral peptide-specific T cell number and function, we show here that heterolo gous virus infections quantitatively delete and qualitatively alter the mem ory pool of T cells specific to a previously encountered virus. We also sho w that a prior history of a virus infection can alter the hierarchy of the immunodominant peptide response to a second virus and that virus infections selectively reactivate memory T cells with distinct specificities to earli er viruses. These results are consistent with a model for the immune system that accommodates memory T cell populations for multiple pathogens over th e course of a lifetime.