Induction of acquired cellular resistance following transfer of thymus-dependent lymphocytes from syphilitic rabbits.

Syphilitic rabbits have previously been shown to resist challenge with Listeria monocytogenes. Thirty days after rabbits were infected with Treponema pallidum, transfer of 4 to 6 times 10-8 viable spleen cells along with T. pallidum conferred resistance to Listeria on normal recipients. Treatment of the spleen cells with anti-thymus serum and complement inhibited or abolished their ability to transfer resistance to Listeria. These results support the hypothesis that the ability of syphilitic rabbits to suppress the growth of Listeria reflects stimulation of cell-mediated immunity during active infection with T. pallidum.