FIG.3.

Survival (solid lines) and parasitemia (dotted lines) of BALB/c, IL-4^−/−, and IL-4rα^−/− mice i.v. infected with 400 sporozoites and treated with L-NIL (a) or aminoguanidine (AG) (b) 1 day before infection until 2 days p.i. All animals treated with L-NIL died (a). Statistical analyses of the survival rates were done with the Kaplan-Meier test, and significant differences were found between the L-NIL-treated groups and the untreated groups. Similar results were observed by using aminoguanidine instead of L-NIL (b). The survival rate of the untreated BALB/c wild type mice in this experiment was 50%. This result was different from the survival rates in the experiments shown in Fig. 1, due to lower infectivity of this sporozoite preparation, and represents the interexperimental variation. Analyses of the parasitemia from the L-NIL (a)- or aminoguanidine (b)-treated groups of mice showed no significant differences at day 8 p.i. The BALB/c mouse group treated with L-NIL (a) or aminoguanidine (b) developed a significantly higher parasitemia at day 15 p.i. than the L-NIL (a)- or aminoguandine (b)-treated KO groups. Each group contained four animals. The data are representative of two independent experiments. The sporozoites were prepared from one batch of infected A. stepehensi mosquitoes. All groups of mice were infected with this batch to avoid differences in the survival rates in one experiment due to different viabilities of the sporozoites. (c) Survival (solid lines) and parasitemia (dotted lines) of BALB/c, IL-4^−/−, and IL-4rα^−/− mice i.v. infected with 400 sporozoites. Depletion of NK cells was achieved by i.v. treatment with anti-asialo GM₁ antibody 1 day before the infection. Control groups of mice were given normal rabbit serum. Parasitemia of anti-asialo GM₁ antibody-treated BALB/c mice demonstrated no significant differences at day 8 p.i. versus NK cell-depleted KO groups. NK cell-depleted BALB/c mice developed a significantly higher parasitemia at day 12 p.i. than the NK cell-depleted KO mouse groups. Statistical analyses of the survival rates were done with the Kaplan-Meier test. The NK cell-depleted groups showed significantly higher lethality than the normal rabbit serum-treated groups. Each group contained five animals. The data are representative of two independent experiments. The sporozoites were prepared from one batch of infected A. stepehensi mosquitoes. All groups of mice were infected with this batch to avoid differences in the survival rates in one experiment due to different viabilities of the sporozoites.