TABLE 1.

Trypanocidal activity in and NO release of IFN-γ-activated macrophages from WT and TNFRp55^−/− mice^a

IFN-γ added	WT			TNFRp55−/−
	No. of parasites/100 cells (% infected cells)	NO2− release (μM)		No. of parasites/100 cells (% infected cells)	NO2− release (μm)
		Medium	Medium + l-NIL		Medium	Medium + l-NIL
No	273 ± 50 (28 ± 7)	2 ± 2	3 ± 2	351 ± 58 (35 ± 7)	11 ± 9	5 ± 1
Yes	10 ± 6b (5 ± 3)c	49 ± 1c	3 ± 2	36 ± 2b (3 ± 1)c	79 ± 16c	6 ± 3

^aRecombinant murine IFN-γ (5 U/ml) and/or 0.5 mM l-NIL was added to macrophages 24 h before infection with T. cruzi. Four hours after infection, free parasites were washed and reagents were replenished. The nitrite concentration in the supernatant was measured by the Griess assay 3 days after infection. Supernatants from noninfected cells contained nondetectable levels of nitrite after 4 days in culture. The mean numbers of infected cells and the numbers of parasites per 100 cells ± standard errors of the means from triplicate determinations as recorded 48 h after infection are shown. 

^bDifference from the nontreated infected control value is significant (P < 0.05, Mann-Whitney-U Wilcoxon test). 

^cDifference from the nontreated infected control value is significant (P < 0.05, Pearson chi-square test).