FIG. 8.

Protection against secondary Listeria infection does not require soluble TNF. (A) WT and memTNF mice were infected with 200 CFU of Listeria intravenously, and 8 weeks after the initial infection, naïve and immune mice were infected with 10⁵ CFU of Listeria. The data are the time to euthanasia for between 8 and 10 mice/group. Significance was determined by the log rank Mantel-Cox test. The asterisk indicates that the P value was <0.001 for a comparison of immune and naïve mice. (B) WT and memTNF mice were infected with 200 CFU of Listeria intravenously, and 14 days later, single-spleen-cell suspensions were prepared from immune and naïve mice, and T cells were isolated by negative selection (CD3⁺, >90%). Two hundred colony-forming units of Listeria and 5 × 10⁶ purified T cells were injected intravenously into TNF^−/− mice that had been irradiated 24 h previously with 500 rads. The data are the time to euthanasia for 11 to 15 mice/group. Significance was determined by the log rank Mantel-Cox test. The dagger indicates that the P value was <0.002 for comparisons of WT immune and WT naïve mice and memTNF immune and memTNF naïvemice.