Resolution of primary murine listeriosis and acquired resistance to lethal secondary infection can be mediated predominantly by Thy-1+ CD4CD8- cells

monoclonal antibody treatment were tested for their ability to express resistance against a pri-mary and secondary Listeria monocytogenes infection. It was found that mice depleted of CDS+, CD4+, or both of these subsets of T cells remained capable of controlling and then resolving both a primary infection and a secondary infection lethal for normal animals. In contrast, depleting mice of a population of Thy-l + CDS- CD4- cells that remain after CD4+ and CDS+ T cells had been removed, rendered them incapable of resolving a sublethal primary infection or of express-ing acquired immunity to a lethal secondary infection. The results point to the possibilities that Thyl + CD4- CDS- a{3 T cells, Thyl + CD4- CDS- 'YO T cells, Thy-l + NK cells, or all three types of these host cells are involved in anti-L. monocytogenes resistance. A substantial amount of evidence has accumulated over the past 30 years [1-3] showing that immunity in mice to infection with the facultative intracellular bacterium, Lis-teria monocytogenes, is T cell mediated. All of this evidence, however, is based on the results ofan adoptive immunization assay that shows that splenic or exudate T cells from mice i