ABSTRACT
The adoptive transfer of resistance to Listeria monocytogenes can be significantly enhanced by in vitro incubation of primed murine spleen cells with concanavalin A (ConA) before transfer into syngeneic recipients. The level of transferred resistance, as measured by clearance of infectious organisms, can approach that observed in actively immunized mice. When delayed-type hypersensitivity (DTH) responses of passive transfer recipients were compared, there was no difference in the level of hypersensitivity exhibited by mice receiving either nonstimulated or ConA-stimulated, Listeria-immune spleen cells. In addition, the level of these adoptively transferred responses never approached the level of DTH observed in actively immunized mice. This inability of ConA-stimulated cells to enhance passive DTH in recipient mice was not dependent on the antigenic preparation of Listeria used to elicit the DTH response. Transfer of cultured, ConA-stimulated, Listeria-immune spleen cells did not lead either to specific or to nonspecific suppression of DTH responsiveness in actively immunized mice. These results indicate the possible existence of antigen-specific T-cells subpopulations which, after stimulation with ConA, exhibit differing efficiencies when responding in assays of cell-mediated immunity.
