Spleen cells of mice infected with Listeria monocytogenes were adoptively transferred to normal mice. Such lymphocytes conferred resistance to a lethal challenge with Listeria. Hyperimmunization of the donor reduces the number of cells necessary to transfer effective immunity. Such spleen cells if treated with anti-θ serum do not transfer resistance to Listeria. Hence, thymus (T) lymphocytes are involved in the resistance to infection with the facultative intracellular bacteria L. monocytogenes
