Mice Deficient in T-bet Form Inducible NO Synthase-Positive Granulomas That Fail to Constrain Salmonella.

ABSTRACT: Clearance of intracellular infections caused by Salmonella Typhimurium (STm) requires IFN-? and the Th1-associated transcription factor T-bet. Nevertheless, whereas IFN-?-/- mice succumb rapidly to STm infections, T-bet-/- mice do not. In this study, we assess the anatomy of immune responses and the relationship with bacterial localization in the spleens and livers of STm-infected IFN-?-/- and T-bet-/- mice. In IFN-?-/- mice, there is deficient granuloma formation and inducible NO synthase (iNOS) induction, increased dissemination of bacteria throughout the organs, and rapid death. The provision of a source of IFN-? reverses this, coincident with subsequent granuloma formation and substantially extends survival when compared with mice deficient in all sources of IFN-?. T-bet-/- mice induce significant levels of IFN-?- after challenge. Moreover, T-bet-/- mice have augmented IL-17 and neutrophil numbers, and neutralizing IL-17 reduces the neutrophilia but does not affect numbers of bacteria detected. Surprisingly, T-bet-/- mice exhibit surprisingly wild-type-like immune cell organization postinfection, including extensive iNOS+ granuloma formation. In wild-type mice, most bacteria are within iNOS+ granulomas, but in T-bet-/- mice, most bacteria are outside these sites. Therefore, Th1 cells act to restrict bacteria within IFN-?-dependent iNOS+ granulomas and prevent dissemination.

SUBMITTER: Perez-Toledo M 

PROVIDER: S-EPMC7372318 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature