Dynamic changes in thymic sub-populations during acute and long-term infections with virulent and virulence-attenuated Salmonella Typhimurium strains in C57BL/6 and autoimmune-prone lpr mice

Salmonella: Typhimurium infection in mice results in drastic loss of immature CD4- CD8- double negative (DN) and CD4+ CD8+ double positive (DP) thymic subsets compared to mature single positive (SP) subsets. We investigated changes in thymocyte sub-populations post infection with a wild type (WT) virulent strain and Delta rpoS, a virulence-attenuated strain, of Salmonella Typhimurium in C57BL/6 (B6) and Fas-deficient autoimmune-prone lpr mice. The WT strain caused acute thymic atrophy with greater loss of thymocytes in lpr mice compared to B6 mice. Infection with Delta rpoS caused progressive thymic atrophy in B6 and lpr mice. Analysis of thymocyte subsets revealed that immature thymocytes including the DN, immature single positive (ISP), and DP thymocytes underwent extensive loss. SP thymocytes were more resistant to loss in WT-infected B6 mice, whereas WT-infected lpr and Delta rpoS-infected mice exhibited depletion of SP thymocytes. Overall, thymocyte sub-populations exhibited differential susceptibilities depending on bacterial virulence and the host background.

Automated summary

Salmonella Typhimurium infection in mice causes significant loss of immature double negative and double positive thymic subsets, while mature single positive subsets are more resistant. The study investigated the impact of a wild type virulent strain and a virulence-attenuated strain on the thymocyte sub-populations in different mouse strains. The results showed that the virulent strain caused acute thymic atrophy, with greater loss of thymocytes in autoimmune-prone mice. The attenuated strain caused progressive thymic atrophy in all mouse strains, with extensive loss of immature thymocytes. The susceptibility of thymocyte sub-populations varied depending on bacterial virulence and host background.