Figure 4. Continuous contact with CFA sustains superior memory.

(A) Naïve CFSE-labeled DO11.10 T cells were transferred into Rag2^−/− and BALB/c mice and the hosts were immunized with 125μg OVA/CFA. Three days later the mice were divided into two groups, the Rag2^−/− mice remained as is (the T cells continue contact with CFA) and the BALB/c mice were used to harvest the LN effectors which were re-transferred into Rag2^−/− mice for parking (no CFA). In this group the T cells are no longer exposed to CFA. Four months later, the splenic cells from both groups were harvested, stimulated with graded concentrations of OVA peptide (triangle) or 10 μM HA peptide (rectangles) as control, and IFNγ responses were measured by ELISA. (B) The LN from the CFA (gray bars) and no CFA (black bars) groups were harvested after 4 or 16 weeks parking and the cells were analyzed for IL-7R expression and apoptosis by 7-AAD using flow cytometry. (C) Naïve CFSE-labeled DO11.10 T cells were transferred into BALB/c mice and the hosts were immunized with 125μg OVA/CFA. Three days later the LN effectors were isolated and re-transferred into Rag2^−/− hosts. One day later, one group of mice was given CFA and the other was left without CFA. After 120 days of parking the spleen cells were harvested and the percent KJ1-26⁺ CD4⁺ T cells were estimated among total splenic cells. The graph represents the mean of four independent experiments. *p< 0.05, **p< 0.01, ***p< 0.005.