FIG 6.

Depletion of Tregs abolishes intradermal low-dose-enhanced susceptibility to T. congolense infection. Groups of mice (n = 4 or 5) were injected weekly with 10² T. congolense parasites or PBS (for 2 consecutive weeks). On the 3rd week, mice were treated with anti-CD25 MAb PC61 (100 μg/mouse) or the isotype-matched control MAb and rechallenged (chall. inf.) with 10³ T. congolense parasites the next day. Daily parasitemia (A) and survival period (B) were monitored as described in Materials and Methods. At the humane endpoint, mice were sacrificed, and sera were assessed for TGF-β (C) and IL-10 (D) by ELISA. In another experiment, groups of mice were injected with anti-CD25 or isotype control MAb (n = 3 or 4 mice/group) at each point of the primary (pri. inf.) low-dose (10² parasites) T. congolense infection (once weekly for 2 weeks). On the 3rd week, the mice were challenged with 10³ T. congolense parasites, and parasitemia (E) and survival period (F) were determined. The data presented are representative of 3 (A to D) and 2 (E and F) different experiments with similar results. Bars show means ± SEM. *, P < 0.05; **, P < 0.01. ns, not significant; ND, not detected (i.e., below the ELISA sensitivity).