Models of the differentiation of memory CD8+ T cells that replicate during secondary infections differ over whether such cells had acquired effector function during primary infections. We created a transgenic mouse line that permits mapping of the fate of granzyme B (gzmB)-expressing CD8+ T cells and their progeny by indelibly marking them with enhanced yellow fluorescent protein (EYFP). Virus-specific CD8+ T cells express gzmB within the first 2 days of a primary response to infection with influenza, without impairment of continued primary clonal expansion. On secondary infection, virus-specific CD8+ T cells that became EYFP+ during a primary infection clonally expand as well as all virus-specific CD8+ T cells. Thus, CD8+ T cells that have acquired an effector phenotype during primary infection may function as memory cells with replicative function.
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Animals, CD8-Positive T-Lymphocytes, Cell Differentiation, Cell Division, Granzymes, Immunologic Memory, Influenza A Virus, H1N1 Subtype, Influenza A Virus, H3N2 Subtype, Luminescent Proteins, Lung, Mice, Mice, Transgenic, Orthomyxoviridae Infections, Phenotype, Spleen, T-Lymphocyte Subsets