Figure 5.

T_EM cells migrating into reactive lymph nodes maintain DCs in a mature immunostimulatory state. (a, d, and g) Experimental design. (a) Mice were transferred with Thy1.1⁺ DO11.10 OVA-specific T cells and either left untreated or primed with one or two s.c. injections of OVA-pulsed DCs to generate T_EM cells and acute or chronic reactive lymph nodes. Some mice were injected weekly with 100 μg of control antibodies or anti-CD62P blocking antibodies. (b) Expression of CD40 and MHC class II on CD11c⁺ DCs purified 30 d after priming from resting (gray lines) or reactive (black lines) lymph nodes. (c) On day 30, mice were transferred with CFSE-labeled HA-specific 6.5 naive T cells and challenged with an i.v. injection of 10 μg HA in PBS. Shown are the percentages and the CFSE profiles of 6.5⁺ T cells in resting or reactive lymph nodes 5 d after challenge. (d) Mice received an s.c. injection of CFA to generate chronic reactive lymph nodes. Control mice received an s.c. injection of PBS. (e) Expression of CD40 and MHC class II on CD11c⁺ DCs purified 30 d after priming from resting or chronic reactive lymph nodes. (f) On day 30, mice were transferred with CFSE-labeled 6.5 naive T cells and challenged with an i.v. injection of 10 μg of HA protein in PBS. Shown are the percentages and the CFSE profiles of 6.5⁺ T cells in resting or chronic reactive lymph nodes 5 d after challenge. (g) Naive mice were adoptively transferred with CFSE-labeled 6.5 naive T cells, and a reactive lymph node was induced by s.c. injection of LPS. 5 d later, mice received an s.c. injection of HA in PBS together with an i.v. transfer of DO11.10 T_EM cells that had been treated with control or CD40L-blocking antibodies. (h) Proliferative response of 6.5⁺ T cells in reactive lymph nodes in the absence or presence of untreated or anti-CD40L–treated T_EM cells. Results are representative of two to five separate experiments.