Tissue gamma/delta T cells in experimental urinary tract infection relationship between other immuno-competent cells

We studied the gamma/delta T cells, which are thought to be one of the local immune-defense system, in an experimental ascending urinary tract infection model in mouse. The experimental infection was induced in the BALB/c mouse by transurethral instillation of Escherichia coli. gamma/delta T cells were stained immunohistochemically with ABC method and the localization in the uninfected and infected murine urinary tract was determined. Then, to determine the CD4 or CD8 phenotype of gamma/delta T cells in the infected site, a two-color immunohistological study was done. In the uninfected state, gamma/delta T cells were observed in the bladder epithelium and submucosa, not in the kidney. It is thought that the difference of gamma/delta T cell distribution between kidney and bladder is affected by the bacteriological milieu, because the chance for foreign antigen exposure of bladder may be greater than that of the kidney. Six hours after inoculation of E. coli, the gamma/delta T cells infiltrated in to the bladder and kidney, following a gradual increase in number. Especially at 105 days after inoculation, severe accumulation of gamma/delta T cells in the renal scarring lesion was observed. Two-color immunohistological study revealed that the phenotypes of gamma/delta T cells in the renal scarring lesion were both CD4-CD8- double negative and CD4-CD8+ single positive. The CD4-CD8+ gamma/delta T cells were probably activated by the bacterial antigen.