As depicted in Fig. 3A, a clear upregulated pattern of expression of CD40, CD80 and CD86, but not CD40L, can be seen on the surface of CD11c+PDCA-1+
cells obtained from the LN. In contrast, we detect only the upregulation of CD40 on CD11c+PDCA-1+ splenocytes at day 10 after infection (Fig. 3B). In addition, we also stained LN and spleen cells for CD11c expression in conjuction with CD8α in addition to the activation markers CD40, CD40L, and CD86 at different times after infection. A limited pattern of upregulation of expression of Lumacaftor cell line CD86 can be seen on the surface of CD11c+CD8α+ cells collected from the LN or spleen on days 3–7 following infection (Fig. 4A and B). Similar analyses were also conducted for CD11C+CD8a− cells collected
from the spleen and LN, but we did not detect an upregulation of expression of the activation markers CD40, CD40L, CD80, or CD86 at any time point from 3 to 30 days in the spleen or LN (data not shown). To determine whether indeed CD11c+PDCA-1+ cells could present antigen for specific CD8 lymphocytes, we purified CD11c+PDCA-1+. After sorting the cells from naïve or 5-day infected Selleckchem Trichostatin A LN cells, we obtained cells that were 95.3 and 83% pure as determined by the PDCA-1 marker (Fig. 5A and B, respectively). For some unknown reason, during the purification process, some cells become negative for the marker for CD11c marker but still
retained the PDCA-1 marker. The PDCA-1+ cells obtained from mice that were infected expressed significantly higher amounts of MHC-II-IAb and CD80 (Fig. 5C and D, respectively). PDCA-1+ Urease cells were used to stimulate purified CD8+ splenic cells obtained from T. cruzi infected mice. As shown in Fig. 5E, IFN-γ producing cells were detected only when CD8+ were incubated with PDCA-1+ cells obtained from infected mice. The fact that CD11c+ cells from the spleen exhibit a limited activation phenotype suggested that perhaps most of the specific T cells found in the spleen might not be primed there. If this assumption is correct, the re-circulation of T cells could account for the CD8+ T-cell mediated functions detected in this organ. To test whether lymphocyte re-circulation was responsible for the immune response observed in the spleen, we treated infected mice with FTY720. This immunosupressive drug inhibits S1P1 signalling, thus efficiently blocking re-circulation of naïve and activated T cells from the LNs into peripheral tissues, thereby preventing development peripheral T-cell responses ,  and . Mice were infected with T. cruzi parasites and FTY720 or diluent were administered on the same day of challenge and every 2 days thereafter as described in Section 2.