Transfer of protection to murine typhoid conferred by L-form Salmonella typhimurium in dependence of cooperation between L form-adopted macrophages and L form-induced Lyt-2+ T cells.

The effector cells responsible for protection to Salmonella typhimurium in C3H/HeJ mice, conferred by L-form S. typhimurium, were determined by cell transfer test. Nonfractionated spleen cells from 6-week immune mice but not from 24-week immune animals transferred anti-S. typhimurium immunity. Treatment with anti-macrophage antiserum and complement most effectively abolished protective capacity in 6-week immune cells, while anti-T cell monoclonal antibody plus complement reduced it to a lesser extent. However, adoptive protection was achieved only by transfer of immune macrophages along with Lyt-2+ T cells selected from 6-week immune spleen cells. These Lyt-2+ T cells were cytotoxic to Kupffer cells from C3H/HeJ mice which had been infected 48 hr previously and from the mice which had been immunized 1 week previously, but not to the cells from 6-week immune mice and from normal animals. Moreover, protective capacity in immune macrophages seemed to be correlated to the degree of colonization by the L forms, and the inability to transfer immunity of 24-week immune spleen cells may be due to the decrease in the L form-colonization. These results suggest that cooperation between the L form-colonized macrophages and L form-induced cytotoxic Lyt-2+ T cells contributes to anti-S. typhimurium immunity, and might imply the immunological difference between the 6-week immune phagocytes and the cells at an early stage of infection or immunization.