Role of T lymphocytes in liver abscess formation by Bacteroides fragilis in mice.

The underlying mechanisms of liver abscess formation have not been fully elucidated with regard to the interaction between bacterial virulence factors and the immune response. The objective of this study was to determine the role of the host T cells in liver abscess formation caused by Bacteroides fragilis. We developed a liver abscess mouse model with inoculation of B. fragilis through the hepatic portal vein and examined the role of T cells by studying T cell-deficient mice, as well as conducting adoptive T cell transfer experiments. No microabscess was formed in the αβ T cell receptor-positive (αβTCR(+)) T cell-depleted mice, in contrast to the results for the control mice. In addition, the αβTCR knockout (KO) mice showed significantly lower numbers of microabscesses, and the abscesses were smaller in size than those in the wild-type mice. Adoptive transfer of T cells purified from the wild-type mice into the αβTCR KO mice resulted in liver abscess formation in those mice. These findings suggest that T cells play an essential role in liver abscess formation caused by B. fragilis in mice.