FIG. 3.

Course of parasitemia and survival in immunized CD4⁺ T cell depleted A/J mice or in wild-type or GKO C57BL/6 mice. To deplete CD4⁺ in vivo, A/J mice were treated i.p. with GK1.5 monoclonal antibody or with an equivalent amount of rat IgG as a control 3 days prior to challenge infection and three times per week during infection. Two weeks after boosting, mice were challenged i.p. with 10⁶ P. chabaudi AS PRBC and the course of parasitemia was determined (A). Female wild-type (B) and GKO (C) C57BL/6 mice were immunized with antigen (Ag) plus IL-12 in alum, and 2 weeks after boosting, mice were challenged i.p. with 10⁶ P. chabaudi AS PRBC and the course of parasitemia was determined. Similar results were obtained in a replicate experiment using male wild-type and GKO mice. In panel A, the asterisk designates a P value of <0.001 for control versus CD4⁺-T-cell-depleted mice. In panel B, the asterisk designates a P value of <0.0001 for untreated versus immunized C57BL/6 mice.