Direction of the cross between A/J and C57BL/6 mice determines gender differences in the susceptibility to infection of the F1 offspring.

<p>Age-matched A/J, C57BL/6, F1(AXB) (offspring of A/J females and C57BL/6 males) and F1(BXA) (offspring of C57BL/6 females and A/J males) mice were infected i.p. with 1000 trypomastigotes of the Y strain of <i>T. cruzi</i>. Mortality of female (A) and male (B) mice was evaluated by daily inspection of the cages. Mouse numbers were as follows: A/J male (n = 10), A/J female (n = 10), C57BL/6 male (n = 11), C57BL/6 female (n = 08), F1(AXB) male (n = 08), F1(AXB) female (n = 11), F1(BXA) male (n = 7) and F1(BXA) female (n = 8). (C) Parasitemia of male mice was quantified by microscopically counting the parasites in 5 μl of citrated blood obtained from the tail lateral vein on days 7, 9, 11 and 13 post-infection. Data shown is one representative experiment of those found in three independent experiments. (*), (#), and (&) indicate <i>P</i><0.05 in relation to C57BL/6, A/J and F1(BXA) respectively. (D) Parasitemia of F1(AXB) (open triangle) and F1 (BXA) (closed triangle) male mice on days 7, 9, 11, 13 post-infection. The data shown is a pool of 8 independent experiments; each plotted symbol represents the parasitemia of a single mouse. (*) indicates <i>P</i><0.05.