Active and memory immunity to Listeria monocytogenes infection in mice is mediated by phenotypically distinct T-cell populations.

The results of this study show that acquired protective immunity to Listeria monocytogenes, measured as the capacity of splenic T cells to passively transfer acquired resistance to normal syngeneic recipients, was mediated by a population of cyclophosphamide-sensitive CD4- CD8+ T cells. The results further show, in contrast, that memory immunity to listeriosis, which was defined as resistance transferred by T cells harvested from infected animals that had received ampicillin chemotherapy, was shown to be mediated by cyclophosphamide-resistant CD4+ CD8- T cells.