Figure 4.

Classical macrophage activation is not altered in IL-13^tg mice after infection with T. cruzi. Transgene-negative littermate control (closed bars) and IL-13^tg (closed bars) mice were infected i.p. with 500 T. cruzi blood trypomastigotes. (A,B) mRNA expression of Irgm (A) and Nos2 (B) in spleens were quantified by real-time PCR at the indicated time points post infection (“moribund” indicates the time point at which the first animal had to be euthanized; 16 days post infection in this particular experiment). Results are expressed as the means ±SD of 4–6 mice per group of one representative out of two experiments. Statistical analysis was performed using the Mann Whitney U test defining differences between IL-13^tg and wildtype mice as significant (^**p ≤ 0.01). (C) For immunohistochemical analysis, spleens were isolated at the time point “moribund” at which the first animal had to be euthanized (16 days post infection in this particular experiment). Histological sections were stained for NOS2 and counterstained with hematoxylin. Representative photomicrographs from 4 to 6 mice per group of one representative out of two experiments are shown (bar, 200 μm; arrow, NOS2-positive cells). (D) Nitrate/nitrite levels in spleen homogenates were determined by the Griess reaction after reduction of nitrate to nitrite. Results are expressed as means of 4–6 mice per group of one experiment.