RESOLUTION OF PRIMARY MURINE LISTERIOSIS AND ACQUIRED-RESISTANCE TO LETHAL SECONDARY INFECTION CAN BE MEDIATED PREDOMINANTLY BY THY-1+ CD4- CD8- CELLS

Mice depleted of CD4+, CD8+, Thy-1+ CD4- CD8-, or all three types of cells by appropriate monoclonal antibody treatment were tested for their ability to express resistance against a primary and secondary Listeria monocytogenes infection. It was found that mice depleted of CD8+, 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-1+ CD8- CD4- cells that remain after CD4+ and CD8+ T cells had been removed, rendered them incapable of resolving a sublethal primary infection or of expressing acquired immunity to a lethal secondary infection. The results point to the possibilities that Thy1+ CD4- CD8- alpha-beta T cells, Thy1+ CD4- CD8- gamma-delta T cells, Thy-1+ NK cells, or all three types of these host cells are involved in anti-L. monocytogenes resistance.