Fig 2.

Analysis of CD4⁺ and CD8⁺ splenocytes 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 euthanized 1 to 2 months after the last challenge dose and the spleen cell suspensions analyzed for (A) total numbers of CD4⁺, CD8⁺, and B (B220⁺) cells, (B) numbers of CD4⁺ and CD8⁺ cells producing IFN-γ, either spontaneously or after in vitro stimulation for 12 h with anti-CD3/anti-CD28 MAbs, and (C) frequencies of proliferating (CFSE^LOW) CD4⁺ and CD8⁺ cells in response to stimulation with anti-CD3 (α-CD3)/anti-CD28 MAbs, T. cruzi antigen (Tc Ag), or medium alone (—). Data represent the results determined with unchallenged (■) and challenged (□) chronically infected mice. *, P < 0.05; *, P < 0.01; #, P < 0.001 (compared to unchallenged chronically infected mice). Representative experiments are shown.