Fig 3.

Analysis of functional polarization in chronically infected mice that were subjected to sustained challenge with homologous T. cruzi parasite cells. Unchallenged mice, chronically infected mice, and chronically infected mice that were submitted to sustained challenge with homologous parasites were bled and euthanized 1 to 2 months after the last challenge dose and analyzed for (A) T. cruzi-specific serum IgG2a and IgG1 antibody levels (O.D values, 1/12,000 dilution), (B) in vitro T. cruzi antigen-induced production of TH1 and TH2 cytokines by spleen cells, and (C) the numbers of CD4⁺ FoxP3⁺ cells in the spleen. Data represent the results determined with unchallenged (■) and challenged (□) chronically infected mice. In panel B, the horizontal bars represent the mean values of cytokine levels in T. cruzi antigen-stimulated spleen cell cultures from noninfected mice. *, P < 0.05; **, P < 0.01; #, P < 0.001 (compared to unchallenged chronically infected mice). Representative experiments are shown.